/usr/share/doc/ghostscript/Language.htm is in ghostscript-doc 9.06~dfsg-2+deb8u7.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=us-ascii">
<title>Ghostscript and the PostScript language</title>
<!-- Originally: language.txt -->
<link rel="stylesheet" type="text/css" href="gs.css" title="Ghostscript Style">
</head>
<body>
<!-- [1.0 begin visible header] ============================================ -->
<!-- [1.1 begin headline] ================================================== -->
<h1>Ghostscript and the PostScript language</h1>
<!-- [1.1 end headline] ==================================================== -->
<!-- [1.2 begin table of contents] ========================================= -->
<h2>Table of contents</h2>
<blockquote><ul>
<li><a href="#Capabilities">Ghostscript's capabilities in relation to PostScript</a>
<li><a href="#Implementation_limits">Implementation limits</a>
<ul>
<li><a href="#Architectural_limits">Architectural limits</a>
<li><a href="#Typical_memory_limits">Typical memory limits in LanguageLevel 1</a>
<li><a href="#VM_consumption">Other differences in VM consumption</a>
</ul>
<li><a href="#Additional_operators">Additional operators in Ghostscript</a>
<ul>
<li><a href="#Graphics_and_text">Graphics and text operators</a>
<ul>
<li><a href="#Transparency">Transparency</a>
<ul>
<li><a href="#Transparency_graphics_state_operators">Graphics state operators</a>
<li><a href="#Transparency_rendering_stack_operators">Rendering stack operators</a>
<li><a href="#Transparency_ImageType">New ImageType</a>
</ul>
<li><a href="#Graphics_state">Other graphics state operators</a>
<li><a href="#Path">Path operators</a>
<li><a href="#Painting">Painting operators</a>
<li><a href="#Character">Character operators</a>
</ul>
<li><a href="#Other">Other operators</a>
<ul>
<li><a href="#Mathematical">Mathematical operators</a>
<li><a href="#Dictionary">Dictionary operators</a>
<li><a href="#String">String and name operators</a>
<li><a href="#Relational">Relational operators</a>
<li><a href="#File">File operators</a>
<li><a href="#Virtual_memory">Virtual memory operators</a>
<li><a href="#Miscellaneous">Miscellaneous operators</a>
<li><a href="#Device">Device operators</a>
</ul>
</ul>
<li><a href="#Filters">Filters</a>
<ul>
<li><a href="#Standard_filters">Standard filters</a>
<li><a href="#Non_standard_filters">Non-standard filters</a>
<li><a href="#Unstable_filters">Unstable filters</a>
</ul>
<li><a href="#Device_parameters">Device parameters</a>
<li><a href="#Banding_parameters">Banding parameters</a>
<li><a href="#User_parameters">User parameters</a>
<li><a href="#Miscellaneous_additions">Miscellaneous additions</a>
<ul>
<li><a href="#Extended_semantics_of_run">Extended semantics of 'run'</a>
<li><a href="#DecodingResources">Decoding resources</a>
<li><a href="#CIDDecodingResources">CIDDecoding resources</a>
<li><a href="#GlyphNames2Unicode">GlyphNames2Unicode</a>
<li><a href="#MultipleResourceDirectories">Multiple Resource directories</a>
</ul>
</ul></blockquote>
<!-- [1.2 end table of contents] =========================================== -->
<!-- [1.3 begin hint] ====================================================== -->
<p>For other information, see the <a href="Readme.htm">Ghostscript
overview</a>.
<!-- [1.3 end hint] ======================================================== -->
<hr>
<!-- [1.0 end visible header] ============================================== -->
<!-- [2.0 begin contents] ================================================== -->
<h2><a name="Capabilities"></a>Ghostscript's capabilities in relation to PostScript</h2>
<p>
The Ghostscript interpreter, except as noted below, is intended to execute
properly any source program written in the (LanguageLevel 3)
<b>PostScript</b> language as defined in the <cite>PostScript
Language Reference, Third Edition</cite> (ISBN 0-201-37922-8) published by
Addison-Wesley in mid-1999. However, the interpreter is configurable in
ways that can restrict it to various subsets of this language.
Specifically, the base interpreter accepts the Level 1 subset of the
PostScript language, as defined in the first edition of the <cite>PostScript
Language Reference Manual</cite> (ISBN 0-201-10174-2) Addison-Wesley 1985,
plus the file system, version 25.0 language, and miscellaneous additions
listed in sections A.1.6, A.1.7, and A.1.8 of the Second Edition
respectively, including allowing a string operand for the
"<code>status</code>" operator. The base interpreter may be configured
(see the <a href="Make.htm">documentation on building Ghostscript</a> for
how to configure it) by adding any combination of the following:
<ul>
<li>The ability to process PostScript Type 1 fonts. This facility is
normally included in the interpreter.
<li>The CMYK color extensions listed in section A.1.4 of the Second Edition
(including <code>colorimage</code>). These facilities are available
only if the <code>color</code>, <code>dps</code>, or
<code>level2</code> feature was selected when Ghostscript was built.
<li>The Display PostScript extensions listed in section A.1.3 of the Second
Edition, but excluding the operators listed in section A.1.2. These
facilities are available only if the <code>dps</code> feature or the
<code>level2</code> feature was selected when Ghostscript was built.
<li>The composite font extensions listed in section A.1.5 of the Second
Edition, and the ability to handle Type 0 fonts. These facilities are
available only if the <code>compfont</code> feature or the
<code>level2</code> feature was selected when Ghostscript was built.
<li>The ability to load TrueType fonts and to handle PostScript Type 42
(encapsulated TrueType) fonts. These facilities are available only if the
<code>ttfont</code> feature was selected when Ghostscript was built.
<li>The PostScript Level 2 "filter" facilities except the
<code>DCTEncode</code> and <code>DCTDecode</code> filters. These
facilities are available only if the <code>filter</code>,
<code>dps</code>, or <code>level2</code> feature was selected when
Ghostscript was built.
<li>The PostScript Level 2 <code>DCTEncode</code> and
<code>DCTDecode</code> filters. These facilities are available only if
the <code>dct</code> or <code>level2</code> feature was selected when
Ghostscript was built.
<li>All the other PostScript Level 2 operators and facilities listed in
section A.1.1 of the Second Edition and not listed in any of the other
A.1.n sections. These facilities are available only if the
<code>level2</code> feature was selected when Ghostscript was built.
<li>All PostScript LanguageLevel 3 operators and facilities listed in the
Third Edition, except as noted below. These facilities are available only
if the <code>psl3</code> feature was selected when Ghostscript was built.
<li>The ability to recognize DOS EPSF files and process only the PostScript
part, ignoring bitmap previews or other information. This facility is
available only if the <code>epsf</code> feature was selected when
Ghostscript was built.
</ul>
<p>
Ghostscript currently does not implement the following PostScript
LanguageLevel 3 facilities:
<ul>
<li>Settable <code>ProcessColorModel</code> for page devices, except for
a very few special devices.
<li><code>IODevice</code>s other than <code>%stdin</code>,
<code>%stdout</code>, <code>%stderr</code>, <code>%lineedit</code>,
<code>%statementedit</code>, <code>%os%</code>, and (if configured)
<code>%pipe%</code> and <code>%disk0%</code> through <code>%disk0%</code>.
</ul>
<p>
Ghostscript can also interpret files in the Portable Document Format (PDF)
1.7 format defined in the
<a href="http://www.adobe.com/devnet/pdf/pdf_reference.html"><em>PDF
Reference</em> Version 1.7</a>,
distributed by <a href="http://www.adobe.com/">Adobe Systems
Incorporated</a>, except as noted below. This facility can be
disabled by deselecting the <code>pdf</code> feature
when Ghostscript is built.
<p>
Ghostscript currently implements the majority of non-interactive
features defined in the PDF reference.
<p>
Ghostscript also includes a number of
<a href="#Additional_operators">additional operators</a> defined below that
are not in the PostScript language defined by Adobe.
<hr>
<h2><a name="Implementation_limits"></a>Implementation limits</h2>
<p>
The implementation limits show here correspond to those in Tables B.1 and
B.2 of the Second and Third Editions, which describe the quantities fully.
Where Ghostscript's limits are different from those of Adobe's
implementations (as shown in the Third Edition), Adobe's limits are also
shown.
<h3><a name="Architectural_limits"></a>Architectural limits</h3>
<blockquote><table cellpadding=0 cellspacing=0>
<tr><th colspan=7 bgcolor="#CCCC00"><hr><font size="+1">Architectural limits (corresponds to Adobe table B.1)</font><hr>
<tr valign=bottom>
<th align=left>Quantity
<td>
<th align=left>Limit
<td>
<th align=left>Type
<td>
<th align=left>Adobe
<tr> <td colspan=7><hr>
<tr valign=top> <td>integer
<td>
<td>32-bit
<td>
<td>twos complement integer
<td>
<td>
<tr valign=top> <td>real
<td>
<td>single-precision
<td>
<td>IEEE float
<td>
<td>
<tr valign=top> <td>array
<td>
<td>65535
<td>
<td>elements
<td>
<td>
<tr valign=top> <td>dictionary
<td>
<td>65534
<td>
<td>elements
<td>
<td>65535
<tr valign=top> <td>string
<td>
<td>65535
<td>
<td>characters
<td>
<td>
<tr valign=top> <td>name
<td>
<td>16383
<td>
<td>characters
<td>
<td>127
<tr valign=top> <td>filename
<td>
<td>128*
<td>
<td>characters
<td>
<td>
<tr valign=top> <td><code>save</code> level
<td>
<td>none
<td>
<td>(capacity of memory)
<td>
<td>15
<tr valign=top> <td><code>gsave</code> level
<td>
<td>none
<td>
<td>(capacity of memory)
<td>
<td>13
</table></blockquote>
<p>
* The limit on the length of a file name is 128 characters if the name
starts with a %...% IODevice designation, or 124 characters if it does not.
<h3><a name="Typical_memory_limits"></a>Typical memory limits in LanguageLevel 1</h3>
<blockquote><table cellpadding=0 cellspacing=0>
<tr><th colspan=7 bgcolor="#CCCC00"><hr><font size="+1">Memory limits (corresponds to Adobe table B.2)</font><hr>
<tr valign=bottom>
<th align=left>Quantity
<td>
<th align=left>Limit
<td>
<th align=left>Type
<td>
<th align=left>Adobe
<tr> <td colspan=7><hr>
<tr valign=top> <td><code>userdict</code>
<td>
<td>200
<td>
<td>
<td>
<td>
<tr valign=top> <td><code>FontDirectory</code>
<td>
<td>100
<td>
<td>
<td>
<td>
<tr valign=top> <td>operand stack
<td>
<td>800
<td>
<td>
<td>
<td>500
<tr valign=top> <td>dictionary stack
<td>
<td>20
<td>
<td>
<tr valign=top> <td>execution stack
<td>
<td>250
<td>
<td>
<tr valign=top> <td>interpreter level
<td>
<td>none
<td>
<td>(capacity of memory)
<td>
<td>10
<tr valign=top> <td>path
<td>
<td>none
<td>
<td>(capacity of memory)
<td>
<td>1500
<tr valign=top> <td>dash
<td>
<td>11
<td>
<td>
<tr valign=top> <td>VM
<td>
<td>none
<td>
<td>(capacity of memory)
<td>
<td>240000
<tr valign=top> <td>file
<td>
<td>none
<td>
<td>(determined by operating system)
<td>
<td>6
<tr valign=top> <td>image
<td>
<td>65535
<td>
<td>values (samples × components)<br>for 1-, 2-, 4-, or 8-bit samples
<td>
<td>3300
<tr valign=top> <td>
<td>
<td>32767
<td>
<td>values for 12-bit samples
<td>
<td>3300
</table></blockquote>
<h3><a name="VM_consumption"></a>Other differences in VM consumption</h3>
<p>
Packed array elements occupy either 2 bytes or 8 bytes. The average
element size is probably about 5 bytes. Names occupy 12 bytes plus the
space for the string.
<p>
The garbage collector doesn't reclaim portions of arrays obtained with
<tt>getinterval</tt>, rather it collects entire arrays.
<hr>
<h2><a name="Additional_operators"></a>Additional operators in Ghostscript</h2>
<h3><a name="Graphics_and_text"></a>Graphics and text operators</h3>
<h4><a name="Transparency"></a>Transparency</h4>
<p>
Ghostscript provides a set of operators for implementing the transparency
and compositing facilities of PDF 1.4. These are defined only if the
<code>transpar</code> option was selected when Ghostscript was built. We
do not attempt to explain the underlying graphics model here: for details,
see <a
href="http://partners.adobe.com/asn/developer/technotes.html#acrobat-pdf"
class="offsite">Adobe
Technical Note</a> #5407, "<a
href="http://partners.adobe.com/asn/developer/acrosdk/DOCS/PDF_Transparency.pdf"
class="offsite">Transparency
in PDF</a>". Note, however, that
Ghostscript's model generalizes that of PDF 1.4 in that Ghostscript
maintains separate alpha and mask values for opacity and shape, rather than
a single value with a Boolean that says whether it represents opacity or
shape.
<h5><a name="Transparency_graphics_state_operators"></a>Graphics state
operators</h5>
<dl>
<dt><code><modename> .setblendmode -</code>
<dd>Sets the blending mode in the graphics state. If the mode name is not
recognized, causes a <code>rangecheck</code> error. The initial value of
the blending mode is <code>/Compatible</code>.
</dl>
<dl>
<dt><code>- .currentblendmode <modename></code>
<dd>Returns the current blending mode.
</dl>
<dl>
<dt><code><0..1> .setopacityalpha -</code>
<dd>Sets the opacity alpha value in the graphics state.
The initial opacity alpha value is 1.
</dl>
<dl>
<dt><code>- .currentopacityalpha <0..1></code>
<dd>Returns the current opacity alpha value.
</dl>
<dl>
<dt><code><0..1> .setshapealpha -</code>
<dd>Sets the shape alpha value in the graphics state.
The initial shape alpha value is 1.
</dl>
<dl>
<dt><code>- .currentshapealpha <0..1></code>
<dd>Returns the current shape alpha value.
</dl>
<dl>
<dt><code><bool> .settextknockout -</code>
<dd>Sets the text knockout flag in the graphics state.
The initial value of the text knockout flag is <code>true</code>.
</dl>
<dl>
<dt><code>- .currenttextknockout <bool></code>
<dd>Returns the current text knockout flag.
</dl>
<h5><a name="Transparency_rendering_stack_operators"></a>Rendering stack
operators</h5>
<p>
The interpreter state is extended to include a (per-context) rendering stack
for handling transparency groups and masks (generically, "layers"). Groups
accumulate a full value for each pixel (paint plus transparency); masks
accumulate only a coverage value. Layers must be properly nested, i.e., the
'end' or 'discard' operator must match the corresponding 'begin' operator.
<p>
Beginning and ending layers must nest properly with respect to
<code>save</code> and <code>restore</code>: <code>save</code> and
<code>restore</code> do not save and restore the layer stack. Currently,
layers are not required to nest with respect to <code>gsave</code> and
<code>grestore</code>, except that the device that is current in the
graphics state when ending a layer must be the same as the device that was
current when beginning the layer. THIS AREA IS SUBJECT TO CHANGE.
<dl>
<dt><code><paramdict> <llx> <lly> <urx> <ury>
.begintransparencygroup -</code>
<dd>Begins a new transparency group. The <code>ll/ur</code> coordinates
are the bounding box of the group in the current user coordinate system.
<code>paramdict</code> has the following keys:
<dl>
<dt><code>/Isolated</code>
<dd>(optional) Boolean; default value = <code>false</code>.
<dt><code>/Knockout</code>
<dd>(optional) Boolean; default value = <code>false</code>.
</dl>
</dl>
<dl>
<dt><code>- .discardtransparencygroup -</code>
<dd>Ends and discards the current transparency group.
</dl>
<dl>
<dt><code>- .endtransparencygroup -</code>
<dd>Ends the current transparency group, compositing the group being ended
onto the group that now becomes current.
</dl>
<dl>
<dt><code><paramdict> <llx> <lly> <urx> <ury>
.begintransparencymaskgroup -</code>
<dd>Begins a new transparency mask, which is represented as a group.
The <code>ll/ur</code> coordinates
are the bounding box of the mask in the current user coordinate system.
<code>paramdict</code> has the following keys:
<dl>
<dt><code>/Subtype</code>
<dd>(required) Name, either <code>/Alpha</code> or
<code>/Luminosity</code>.
<dt><code>/Background</code>
<dd>(optional) Array of number.
<dt><code>/TransferFunction</code>
<dd>(optional) Function object (produced by applying
<code>.buildfunction</code> to a Function dictionary).
</dl>
</dl>
<dl>
<dt><code>- .begintransparencymaskimage -</code>
<dd>Begins a new transparency mask, which is represented as a single image.
</dl>
<dl>
<dt><code>- .discardtransparencymask -</code>
<dd>Ends and discards the current transparency mask.
</dl>
<dl>
<dt><code><masknum> .endtransparencymask -</code>
<dd>Ends the current transparency mask, installing it as the current opacity
(<code>masknum</code> = 0) or shape (<code>masknum</code> = 1) mask in
the graphics state.
</dl>
<dl>
<dt><code><masknum> .inittransparencymask -</code>
<dd>Resets the current opacity (<code>masknum</code> = 0) or shape
(<code>masknum</code> = 1) mask to an infinite mask with alpha = 1
everywhere.
</dl>
<h5><a name="Transparency_ImageType"></a>New ImageType</h5>
<p>
The transparency extension defines a new ImageType 103, similar to ImageType
3 with the following differences:
<ul>
<li>The required <code>MaskDict</code> is replaced by two optional
dictionaries, <code>OpacityMaskDict</code> and
<code>ShapeMaskDict</code>. If present, these dictionaries must have a
<code>BitsPerComponent</code> entry, whose value may be greater than 1.
Note that in contrast to ImageType 3, where any non-zero chunky mask value
is equivalent to 1, ImageType 103 simply takes the low-order bits of chunky
mask values.
<li>A <code>Matte</code> entry may be present in one or both mask
dictionaries, indicating premultiplication of the data values. If both
<code>MaskDict</code>s have a <code>Matte</code> entry and the values
of the two <code>Matte</code> entries are different, a
<code>rangecheck</code> error occurs.
<li><code>InterleaveType</code> appears in the <code>MaskDict</code>s,
not the <code>DataDict</code>, because each mask has its own
<code>InterleaveType</code>. <code>InterleaveType</code> 2
(interlaced scan lines) is not supported.
</ul>
<h4><a name="Graphics_state"></a>Other graphics state operators</h4>
<dl>
<dt><code><bool> .setaccuratecurves -</code>
<dd>Sets a graphics state flag that determines whether curves and arcs,
when flattened, always start and end with a line that is a segment of the
tangent; this also causes butt and square caps to be properly perpendicular
to the tangent. <code>initgraphics</code> sets this flag to false, to
match other PostScript implementations.
</dl>
<dl>
<dt><code>- .currentaccuratecurves <bool></code>
<dd>Returns the current value of the accurate curves flag.
</dl>
<dl>
<dt><code><int> .setcurvejoin -</code>
<dd>Obsolete, left for backward compatibility.
<dd>Sets a graphics state parameter that determines how to treat the joins
between the line segments produced when a curve is flattened. The parameter
value may be either -1 or a value acceptable to <code>setlinejoin</code>.
If the parameter value is -1, the join used for flattened curve line
segments is given by the current line join parameter in the graphics state
(except that if the line join value is "none", a bevel join is used), which
matches the Adobe Red Book, but not some old Adobe implementations; if the curve
join parameter value is a line join value, that type of join is used for
flattened curve line segments, regardless of the value of the graphics state
line join parameter. The initial (and default) value of the curve join
parameter is -1, causing the compatibility to Red Book and to modern Adobe
implementations. <code>initgraphics</code> sets the parameter to its
default value.
</dl>
<dl>
<dt><code>- .currentcurvejoin <int></code>
<dd>Obsolete, left for backward compatibility.
<dd>Returns the current value of the curve join parameter.
</dl>
<dl>
<dt><code><bool> .setdashadapt -</code>
<dd>Sets a graphics state flag that determines whether dash patterns do
(true) or do not (false) automatically scale themselves so that each line
segment consists of an integral number of pattern repetitions.
<code>initgraphics</code> sets this flag to false.
</dl>
<dl>
<dt><code>- .currentdashadapt <bool></code>
<dd>Returns the current value of the dash adaptation flag.
</dl>
<dl>
<dt><code><matrix> .setdefaultmatrix -</code>
<dd>Sets the default matrix that is returned by
<code>defaultmatrix</code> and installed by <code>initmatrix</code>.
Ordinary programs should not use this operator.
</dl>
<dl>
<dt><code><num> <bool> .setdotlength -</code>
<dd>Sets a graphics state parameter that determines the handling of
zero-length lines (dots). If the dot length is zero, dots are painted as
circles if round line caps are in effect, otherwise they are not painted at
all. If the dot length is non-zero, dots are treated exactly like lines of
the given length: the length is specified in user coordinates (like line
width) if <code>bool</code> is false, or in default user coordinates of
points (units of 1/72in; see the <a href="Devices.htm#Measurements">notes
on measurements</a> in the documentation on devices) if
<code>bool</code> is true. Dots occurring as part of dash patterns will
be oriented correctly; isolated dots will be oriented as though they were
part of a vertical line. <code>initgraphics</code> sets the dot length
to zero.
</dl>
<dl>
<dt><code>- .currentdotlength <num> <bool></code>
<dd>Returns the current dot length and dot length mode.
</dl>
<dl>
<dt><code><dx> <dy> .setfilladjust2 -</code>
<dd>Sets graphics state parameters that cause all filled and stroked
regions to be "fattened" by the given amount relative to an algorithm that
only paints pixels whose centers fall within the region to be painted.
<code>dx</code> and <code>dy</code> are numbers between 0 and 0.5,
measured in device space. The only two values that are likely to be useful
are 0, which gives a pure center-of-pixel rule, and 0.5, which gives
Adobe's any-part-of-pixel rule. (0.5 is treated slightly specially in
order to create half-open pixels per Adobe's specification.)
</dl>
<dl>
<dt><code>- .currentfilladjust2 <dx> <dy></code>
<dd>Returns the current fill adjustment values.
</dl>
<dl>
<dt><code><bool> .setlimitclamp -</code>
<dd>Sets a graphics state flag that determines whether attempts to set the
current point outside the internally representable range should clamp the
value to the largest representable value (true) or give a
<code>limitcheck</code> error (false). <code>initgraphics</code> sets
this flag to false, to match other PostScript implementations.
</dl>
<dl>
<dt><code>- .currentlimitclamp <bool></code>
<dd>Returns the current value of the limit clamp flag.
</dl>
<dl>
<dt><code><int> .setoverprintmode -</code>
<dd>Sets the overprint mode in the graphics state. Legal values are 0 or 1.
Per the PDF 1.3 specification, if the overprint mode is 1, then when the
current color space is <code>DeviceCMYK</code>, color components whose
value is 0 do not write into the target, rather than writing a 0 value.
THIS BEHAVIOR IS NOT IMPLEMENTED YET. The initial value of the overprint
mode is 0.
</dl>
<dl>
<dt><code>- .currentoverprintmode <int></code>
<dd>Returns the current overprint mode.
</dl>
<h4><a name="Path"></a>Path operators</h4>
<dl>
<dt><code>- .dashpath -</code>
<dd>If there is no current dash pattern, does nothing. Otherwise, does the
equivalent of <code>flattenpath</code> and then chops up the path as
determined by the dash pattern.
</dl>
<dl>
<dt><code><x> <y> <width> <height> .rectappend -</code>
<dt><code><numarray> .rectappend -</code>
<dt><code><numstring> .rectappend -</code>
<dd>Appends a rectangle or rectangles to the current path, in the same
manner as <code>rectfill</code>, <code>rectclip</code>, etc. Defined
only if the <code>dps</code> or <code>level2</code> option was
selected when Ghostscript was built.
</dl>
<dl>
<dt><code>- .getpath <array></code>
<dd>Export the current path to an array of executable arrays. This
operator is similar to <code>upath</code>, except
<ul>
<li>array of arrays is used to overcome 64K-1 limit on the
array lemgth.
<li>no <code>ucache</code> or <code>setbbox</code> entries are generated.
<li>operators are used instead of executable names.
<li>there's no special handling of an empty path or trailing <code>moveto</code>.
The saved path can be restored by <code>newpath { exec } forall</code>.
</ul>
</dl>
<dl>
<dt><code>- .sethpglpathmode</code>
<dd>If the single numerical parameter is non zero, then future path
creation operations will make an HPGL-style path. HPGL style paths
differ from postscript style paths in that moveto operations only
begin a new subpath if there is not already an open subpath. (i.e.
<code>a b moveto c d moveto e f lineto closepath</code> will draw
back to (a,b), not (c,d). HPGL paths treat these non-subpath starting
<tt>moveto</tt>s as <tt>lineto</tt> segments when filling, and as
unstroked gaps when stroking.
</dl>
<dl>
<dt><code>.currenthpglpathmode -</code>
<dd>Leave the current hpglpathmode on the stack. The initial value
of hpglpathmode is 0.
</dl>
<h4><a name="Painting"></a>Painting operators</h4>
<p>
Ghostscript supports an experimental extension of the PostScript imaging
model to include <code>RasterOp</code> and some related facilities.
This extension is available only if the <code>rasterop</code> option was
selected when building Ghostscript.
<p>
With the <code>RasterOp</code> extension, imaging operations compute a
function <b>D = f(D,S,T)</b> in RGB space, where <b>f</b> is an
arbitrary 3-input Boolean function, <b>D</b> is the destination (frame
buffer or print buffer), <b>S</b> is the source (described below), and
<b>T</b> is the texture (the current PostScript color, which may be a
pattern). The source and texture depend on the PostScript imaging
operation:
<ul>
<li>For <code>fill</code> and <code>stroke</code>, the source is
solid black, covering the region to be painted; the texture is the current
PostScript color.
<li>For <code>show</code> and <code>imagemask</code>, the source is
solid black, covering the pixels to be painted; the texture is the current
PostScript color.
<li>For <code>image</code> and <code>colorimage</code>, the source is
the image data; the texture depends on an optional Boolean parameter,
<code>CombineWithColor</code>, in the image dictionary. If
<code>CombineWithColor</code> is false (the default), the texture is
solid black. If <code>CombineWithColor</code> is true, the texture is
the current color. For the non-dictionary form of the image operator,
<code>CombineWithColor</code> is considered to be false.
</ul>
<p>
The <code>rasterop</code> option adds the following operators:
<dl>
<dt><code><int8> .setrasterop -</code>
<dd>Sets the <code>RasterOp</code> function in the graphics state. The
default function is 252, Source | Texture.
</dl>
<dl>
<dt><code>- .currentrasterop <int8></code>
<dd>Returns the current <code>RasterOp</code> function.
</dl>
<dl>
<dt><code><bool> .setsourcetransparent -</code>
<dd>Sets source transparency in the graphics state. When source
transparency is true, white source pixels prevent storing into the
destination, regardless of what the <code>RasterOp</code> function
returns. The default source transparency is false.
</dl>
<dl>
<dt><code>- .currentsourcetransparent <bool> -</code>
<dd>Returns the current source transparency.
</dl>
<dl>
<dt><code><bool> .settexturetransparent -</code>
<dd>Sets texture transparency in the graphics state. When texture
transparency is true, white texture pixels prevent storing into the
destination, regardless of what the <code>RasterOp</code> function
returns. The default texture transparency is false.
</dl>
<dl>
<dt><code>- .currenttexturetransparent <bool> -</code>
<dd>Returns the current texture transparency.
</dl>
<p>
For more information on RasterOp and transparency, please consult chapter 5
of the "PCL 5 Color Technical Reference Manual",
<a href="http://www.hp.com/cposupport/printers/support_doc/bpl01354.html">Hewlett-Packard
Manual Part No. 5961-0635</a>.
<h4><a name="Character"></a>Character operators</h4>
<dl>
<dt><code><string> <bool> .charboxpath -</code>
<dd>For each character <b>C</b> in the rendering of <string>, let the
bounding box of <b>C</b> <b><em>in device space</em></b> be the four
<b><em>user-space</em></b> points p1x/y, p2x/y, p3x/y, and p4x/y. For each
character in order, <code>.charboxpath</code> appends the following to
the current path:
<ul><li>If <code><bool></code> is true, the equivalent of:
<blockquote>
p1x p1y <code>moveto</code><br>
p2x p2y <code>lineto</code><br>
p3x p3y <code>lineto</code><br>
p4x p4y <code>lineto</code><br>
<code>closepath</code>
</blockquote>
</ul>
<p>
This creates a path whose <code>pathbbox</code> is the
<code>bbox</code> of the string.
<ul><li>If <code><bool></code> is false, the equivalent of:
<blockquote>
p1x p1y <code>moveto</code><br>
p3x p3y <code>lineto</code>
</blockquote>
</ul>
<p>
If the CTM is well-behaved (consists only of reflection, scaling, and
rotation by multiples of 90 degrees), this too creates a (simpler) path
whose <code>pathbbox</code> is the <code>bbox</code> of the string.
</dl>
<dl>
<dt><code><font> <charname|charcode> <charname> <charstring> .type1execchar -</code>
<dd>Does all the work for rendering a Type 1 outline. This operator, like
<code>setcharwidth</code> and <code>setcachedevice</code>, is valid
only in the context of a show operator -- that is, it must only be called
from within a <code>BuildChar</code> or <code>BuildGlyph</code>
procedure.
</dl>
<dl>
<dt><code><font> <charcode> %Type1BuildChar -</code>
<dd>This is not a new operator: rather, it is a name known specially to the
interpreter. Whenever the interpreter needs to render a character (during
a ...<code>show</code>, <code>stringwidth</code>, or
<code>charpath</code>), it looks up the name <code>BuildChar</code>
in the font dictionary to find a procedure to run. If it does not find
this name, and if the <code>FontType</code> is 1, the interpreter
instead uses the value (looked up on the dictionary stack in the usual way)
of the name <code>%Type1BuildChar</code>.
<p>
The standard definition of <code>%Type1BuildChar</code> is in the
initialization file <code>gs_type1.ps</code>. Users should not need to
redefine <code>%Type1BuildChar</code>, except perhaps for tracing or
debugging.
</dl>
<dl>
<dt><code><font> <charname> %Type1BuildGlyph -</code>
<dd>Provides the Type 1 implementation of <code>BuildGlyph</code>.
</dl>
<h3><a name="Other"></a>Other operators</h3>
<h4><a name="Mathematical"></a>Mathematical operators</h4>
<dl>
<dt><code><number> arccos <number></code>
<dd>Computes the arc cosine of a number between -1 and 1.
</dl>
<dl>
<dt><code><number> arcsin <number></code>
<dd>Computes the arc sine of a number between -1 and 1.
</dl>
<h4><a name="Dictionary"></a>Dictionary operators</h4>
<dl>
<dt><code>mark <key1> <value1> <key2> <value2> ... .dicttomark <dict></code>
<dd>Creates and returns a dictionary with the given keys and values. This
is the same as the PostScript Level 2 <code>>></code> operator,
but is available even in Level 1 configurations.
</dl>
<dl>
<dt><code><dict> <key> <value> .forceput - </code>
<dd>Equivalent to <code>put</code>, but works even if
<code>dict</code> is not writable, and (if <code>dict</code> is
<code>systemdict</code> or the current save level is 0) even if
<code>dict</code> is in global VM and <code>key</code> and/or
<code>value</code> is in local VM. <strong>This operator should be used
only initialization code, and only in executeonly procedures: it must not be
accessible after initialization.</strong>
</dl>
<dl>
<dt><code><dict> <key> .forceundef - </code>
<dd>Equivalent to <code>undef</code>, but works even if
<code>dict</code> is not writable. <strong>This operator should be used
only initialization code, and only in executeonly procedures: it must not be
accessible after initialization.</strong>
</dl>
<dl>
<dt><code><dict> <key> .knownget <value> true</code>
<dt><code><dict> <key> .knownget false</code>
<dd>Combines <code>known</code> and <code>get</code> in the
obvious way.
</dl>
<dl>
<dt><code><dict> <integer> .setmaxlength -</code>
<dd>Sets the capacity (<code>maxlength</code>) of a dictionary.
Causes a <code>dictfull</code> error if the dictionary has more
occupied entries than the requested capacity.
</dl>
<h4><a name="String"></a>String and name operators</h4>
<dl>
<dt><code><integer> .bytestring <bytestring></code>
<dd>Allocates and returns a bytestring, a special data type that can be
larger than the maximum size of a string (64K-1 bytes) and can be used in
place of a string with a very few operators.
</dl>
<dl>
<dt><code><name> .namestring <string></code>
<dd>Returns the (read-only) string for a name.
</dl>
<dl>
<dt><code><string> <charstring> .stringbreak <index|null></code>
<dd>Searches for a character in <code>string</code> that appears
somewhere in <code>charstring</code>. If such a character is found,
returns the index of the first such character; if no such character is
found, returns <code>null</code>.
</dl>
<dl>
<dt><code><obj> <pattern> .stringmatch <bool></code>
<dd>Matches <code>obj</code> against a pattern in which '*' matches 0 or
more characters and '?' matches any single character. If
<code>obj</code> is a string or a name, matches its characters against
the pattern; if <code>obj</code> is of any other type, the result is
<code>true</code> if the pattern is the single character "*" and
<code>false</code> otherwise.
</dl>
<dl>
<dt><code><state> <fromString> <toString> .type1encrypt <newState> <toSubstring></code>
<dd>Encrypts <code>fromString</code> according to the algorithm for
Adobe Type 1 fonts, writing the result into <code>toString</code>.
<code>toString</code> must be at least as long as
<code>fromString</code>, or a rangecheck error occurs.
<code>state</code> is the initial state of the encryption algorithm (a
16-bit non-negative integer); <code>newState</code> is the new state of
the algorithm.
</dl>
<dl>
<dt><code><state> <fromString> <toString> .type1decrypt <newState> <toSubstring></code>
<dd>Decrypts <code>fromString</code> according to the algorithm for
Adobe Type 1 fonts, writing the result into <code>toString</code>.
Other specifications are as for <code>type1encrypt</code>.
</dl>
<h4><a name="Relational"></a>Relational operators</h4>
<dl>
<dt><code><number|string> <number|string> max <number|string></code>
<dd>Returns the larger of two numbers or strings.
</dl>
<dl>
<dt><code><number|string> <number|string> min <number|string></code>
<dd>Returns the smaller of two numbers or strings.
</dl>
<h4><a name="File"></a>File operators</h4>
<dl>
<dt><code><file> .filename <string> true</code>
<dt><code><file> .filename false</code>
<dd>If the file was opened by the <code>file</code> or
<code>.tempfile</code> operator, returns the file name and
<code>true</code>; if the file is a filter, returns
<code>false</code>.
</dl>
<dl>
<dt><code><file> .fileposition <integer> true</code>
<dd>Returns the position of <code>file</code>. Unlike the standard
<code>fileposition</code> operator, which causes an error if the file is
not positionable, <code>.fileposition</code> works on all files,
including filters: for non-positionable files, it returns the total number
of bytes read or written since the file was opened.
</dl>
<dl>
<dt><code><string> findlibfile <foundstring> <file> true</code>
<dt><code><string> findlibfile <string> false</code>
<dd>Opens the file of the given name for reading, searching through
directories <a href="Use.htm#Finding_files">as described in the usage
documentation</a>. If the search fails, <code>findlibfile</code> simply
pushes false on the stack and returns, rather than causing an error.
</dl>
<dl>
<dt><code><file> <string> .peekstring <substring> <filled_bool></code>
<dd>Reads bytes from a file like <code>readstring</code>, but also leaves
the bytes in the file buffer so they will be read again by a subsequent read
operation. Currently gives a <code>rangecheck</code> error if
<code>string</code> is larger than the file's buffer.
</dl>
<a name=Tempfile></a>
<dl>
<dt><code><prefix_string|null> <access_string> .tempfile
<string> <file></code>
<dd>Creates and opens a temporary file
like the <code>file</code> operator, also returning the file name. There
are three cases for the <code><prefix_string|null></code> operand:
<ul>
<li><code>null</code>: create the file in the same directory and with the
same name conventions as other temporary files created by the Ghostscript
implementation on this platform. E.g., the temporary file might be named
<code>/tmp/gs_a1234</code>.
<p>
<li>A string that contains only alphanumeric characters, underline,
and dash: create the file in the standard temporary directory, but use
the
<code><prefix_string></code> as the first part of the file name.
E.g., if <code><prefix_string></code> is <code>xx</code>, the
temporary file might be named <code>/tmp/xxa1234</code>.
<p>
<li>A string that is the beginning of an absolute file name: use the
<code><prefix_string></code> as the first part of the file name.
E.g., if <code><prefix_string></code> is
<code>/my/tmpdir/zz</code>, the temporary file might be named
<code>/my/tmpdir/zza1234</code>.
<p>
When running in <code>SAFER</code> mode, the absolute path must
be one of the strings on the list given by the <code>PermitFileWriting</code>
userparameter. Temporary files created with <code>.tempfile</code> can
be deleted when in SAFER mode, and can be renamed to one of the paths
that is on <b>both</b> the PermitFileControl and PermitFileWriting
paths.
</ul>
</dl>
<dl>
<dt><code><file> <integer> .unread -</code>
<dd>Pushes back the last-read character onto the front of the file. If the
file is open only for writing, or if the integer argument is not the same
as the last character read from the file, causes an <code>ioerror</code>
error. May also cause an <code>ioerror</code> if the last operation on
the file was not a reading operation. This operator is now deprecated:
use <code>.peekstring</code> in new code.
</dl>
<p>
Ghostscript also supports the following <code>IODevice</code> in
addition to a subset of those defined in the Adobe documentation:
<ul>
<li>
<code>%pipe%command</code>, which opens a pipe on the given command.
This is supported only on operating systems that provide
<code>popen</code> (primarily Unix systems, and not all of those).
<p>
<li>
<code>%disk#%</code>, which emulates the %disk0
through %disk9 devices on some Adobe PostScript printers. This pseudo
device provides a flat filenaming system with a user definable location
for the files (/Root). These devices will only be present if the
diskn.dev feature is specified during the build.
<p>
This feature is intended to allow compatibility with font downloaders
that expect to store fonts on the %disk device of the printer.
<p>
Use of the %disk#% devices requires that the location of files be given
by the user setting the /Root device parameter. The syntax for setting
the /Root parameter is:<pre>
mark /Root (directory_specification) (%disk#) .putdevparams
</pre>
For example, to store the files of the %disk0 device on the directory
/tmp/disk0, use:<pre>
mark /Root (/tmp/disk0/) (%disk0) .putdevparams
</pre>
The files will be stored in the specified directory with arbitrary names.
A mapping file is used to store the association between the file
names given for the file operations on the %diskn# device and the file
that resides in the /Root directory.
</ul>
<h4><a name="Virtual_memory"></a>Virtual memory operators</h4>
<dl>
<dt><code><save> .forgetsave -</code>
<dd>Cancels the effect of a save, making it as though the save never
happened.
</dl>
<h4><a name="Miscellaneous"></a>Miscellaneous operators</h4>
<dl>
<dt><code><array> bind <array></code>
<dd>Depending on the command line parameters <code>bind</code> is redefined as:
</dl>
<blockquote><table cellpadding=0 cellspacing=0>
<tr valign=bottom>
<th valign=bottom align=left>Flag
<td>
<th valign=bottom align=left>Definition
<tr> <td colspan=3><hr>
<tr valign=top> <td>NOBIND
<td>
<td>/bind {} def ;
no operation, returns the argument
<tr valign=top> <td>DELAYBIND
<td>
<td>returns the argument, stores the argument for later use by <code>.bindnow</code>
</table></blockquote>
<dl>
<dt><code><array> .bind <array></code>
<dd>Performs standard <code>bind</code> operation as defined in PLRM regardless of
NOBIND or DELAYBIND flags.
</dl>
<a name="bindnow"></a>
<dl>
<dt><code>- .bindnow -</code>
<dd>Applies <code>bind</code> operator to all savad procedures after binding has been
deferred through -dDELAYBIND. Note that idiom recognition has no effect for the deferred
binding because the value returned from <code>bind</code> is discarded.
<p>
Since v. 8.12 <code>.bindnow</code> undefines itself and restores standard definition of
<code>bind</code> operator. In earlier versions after calling <code>.bindnow</code>,
the postscript <code>bind</code> operator needs to be rebound to the internal implementation
<code>.bind</code>, as in this fragment from the ps2ascii script:
<blockquote><pre><tt>DELAYBIND {
.bindnow
/bind /.bind load def
} if
</tt></pre></blockquote>
This is necessary for correct behavior with later code that uses the <code>bind</code> operator.
</dl>
<dl>
<dt><code><obj1> <obj2> ... <objn> <n> .execn ...</code>
<dd>This executes <code>obj1</code> through <code>objn</code> in that
order, essentially equivalent to
<blockquote><pre>
<obj1> <obj2> ... <objn> <n> array astore {exec} forall
</pre></blockquote>
<p>
except that it doesn't actually create the array.
</dl>
<dl>
<dt><code><string> getenv <string> true</code>
<dt><code><string> getenv false</code>
<dd>Looks up a name in the shell environment. If the name is found,
returns the corresponding value and true; if the name is not found, returns
false.
</dl>
<dl>
<dt><code>.defaultpapersize <string> true</code>
<dt><code>.defaultpapersize false</code>
<dd>Get the system default paper size, which is usually
<code>a4</code> for countries using the metric system, and
<code>letter</code> for countries using the imperial system.
</dl>
<dl>
<dt><code><name> <array> .makeoperator <operator></code>
<dd>Constructs and returns a new operator that is actually the given
procedure in disguise. The name is only used for printing. The operator
has the executable attribute.
<p>
Operators defined in this way do one other thing besides running the
procedure: if an error occurs during the execution of the procedure, and
there has been no net reduction in operand or dictionary stack depth, the
operand or dictionary stack pointer respectively is reset to its position
at the beginning of the procedure.
</dl>
<dl>
<dt><code><string> <boolean> .setdebug -</code>
<dd>Sets or clears any subset of the debugging flags included in
<code><string></code> based on the value of
<code><boolean></code>. These correspond to the debug
flags set by <code>-Z</code> on the command line and enable
debug and tracing output from various internal modules.
<p>Note that most tracing output is only produced if the Ghostscript
interpreter was built with the <code>DEBUG</code> preprocessor
symbol defined.
<p>The <code>zsetdebug()</code> C function, which implements this
operator, is a useful breakpoint for debuggers.
Inserting '<code>() true .setdebug</code>' in the interpreted code will
trigger a breakpoint at that location without side effects. The
current flag state is available in C as the <code>gs_debug[]</code>
array, indexed by character value. The <code>zsetdebug</code> function will
be entered, and <code>gs_debug[]</code> updated, whether or not Ghostscript
is built with the <code>DEBUG</code> preprocessor symbol defined, so this
is useful even with release builds.
</dl>
<dl>
<dt><code>- .oserrno <errno></code>
<dd>Returns the error code for the most recent operating system error.
</dl>
<dl>
<dt><code>- .oserrorstring <string></code>
<dd>Returns the error string for the most recent operating system error.
</dl>
<a name="Runandhide"></a>
<dl>
<dt><code><array> <procedure> .runandhide ... <array></code>
<dd>Runs the <i><tt><procedure></tt></i> after removing the
<i><tt><array></tt></i> from the stack. As long as <i><tt><array></tt></i>
is not contained in any readable dictionaries or elsewhere on stacks, it
will not be accessible to <i><tt><procedure></tt></i>.
<p>
This operator is intended to allow hiding a <i><tt><save></tt></i> object
during execution of procedures or files that run in <b>SAFER</b> mode.
If a <code>save</code> is performed prior to entering <b>SAFER</b> mode
with <code>.setsafe</code>, using the save object as the operand to
<code>restore</code> will return to <b>NOSAFER</b> mode. In order to
prevent the procedures running in <b>SAFER</b> mode from being able to
return to <b>NOSAFER</b> mode, this operator should be used.
Upon return from the file or procedure <code>restore</code> can be used
to return to <b>NOSAFER</b> mode.
<p>
<b>Note:</b> The array operand hidden during the execution of the file or
procedure will be placed at the top of the operand stack which may be on
top of objects that the file or procedure leaves on top of the stack.
Thus removing objects below the array may be needed to prevent an
<code>invalidrestore</code> error.
<p>
For example, in order for a script or job server to execute a file
<tt>somefile.ps</tt> with the <b>SAFER</b> mode restrictions in place, returning
to unrestricted <b>NOSAFER</b> mode when the procedure exits is as follows:
<pre>
Start Ghostscript with <b>-dNOSAFER</b>
... % perform any device set up w/o restrictions
[ save ] % create a save object before SAFER
(somefile.ps) (r) file cvx % open the file to process
.setsafe % enter SAFER mode
.runandhide % run the file hiding the save object
count 1 roll % place array below anything left over
count 1 sub { pop } repeat % pop left over stuff
cleardictstack % prevent invalidrestore from dicts
0 get restore % go back to NOSAFER mode
</pre>
Another refinement on the above would be to execute <code>.runandhide</code>
using <code>stopped</code> in order to report errors but continue processing.
</dl>
<dl>
<dt><code>- .setsafe -</code>
<dd>If Ghostscript is started with <code>-dNOSAFER</code> or
<code>-dDELAYSAFER</code>, this operator can be used to enter <b>SAFER</b>
mode (see <a href="Use.htm#Safer"><b>-dSAFER</b></a>)
<p>
Since <b>SAFER</b> mode is implemented with userparameters and device parameters,
it is possible to use <code>save</code> and <code>restore</code> before
and after <code>.setsafe</code> to return to <b>NOSAFER</b> mode, but care
should be taken to ensure that the <i><tt>save</tt></i> object is not
accessible to any procedures or file run in <b>SAFER</b> mode (see
<a href="#Runandhide"><b>.runandhide</b></a> above).
<p>
<b>Note: This uses setpagedevice to change .LockSafetyParams, so the page
will be erased as a side effect of this operator</b>
</dl>
<dl>
<dt><code>- .locksafe -</code>
<dd>
This operator sets the current device's <code>.LockSafetyParams</code>
and the <code>LockFilePermissions</code> userparameter true as well as
adding the paths on LIBPATH and FONTPATH and the paths given by the
system params /GenericResourceDir and /FontResourceDir to the current
PermitFileReading list of paths.
<p>
If Ghostscript is started with <code>-dNOSAFER</code> or
<code>-dDELAYSAFER</code>, this operator can be used to enter <b>SAFER</b>
mode with the current set of <code>PermitFile...</code> user parameters
in effect. Since <code>.setsafe</code> sets the <code>PermitFile...</code>
user parameters to empty arrays, a script or job server that needs to
enable certain paths for file Reading, Writing and/or Control can use this
operator to perform the locking needed to enter <b>SAFER</b> mode.
<p>
For example, to enable reading everywhere, but disallow writing and file
control (deleting and renaming files), the following can be used:
<pre>
{ << /PermitFileReading [ (*) ]
/PermitFileWriting [ ]
/PermitFileControl [ ]
>> setuserparams
.locksafe
} stopped pop
</pre>
In the above example, use of stopped will allow the use of this sequence on
older versions of Ghostscript where <code>.locksafe</code> was not an operator.
<p>
<b>Note: This uses setpagedevice to change .LockSafetyParams, so the page
will be erased as a side effect of this operator</b>
<p>
See also <a href="#LockSafetyParams">.LockSafetyParams</a> and
<a href="#User_parameters">User Parameters</a>.
<p>
</dl>
<dl>
<dt><a name=".setpdfwrite"></a>
<code>.setpdfwrite</code></dt>
<dd>This operator conditions the environment for the <tt>pdfwrite</tt> output device.
It is a shorthand for setting parameters that have been deemed benificial. While not strictly necessary, it is usually helpful to set call this when using the pdfwrite device.
For example, this is how the ps2pdf script calls Ghostscript:
<blockquote><code>
gs -q -dSAFER -dNOPAUSE -dBATCH -sOutputFile=file.pdf </code><em>[more options]</em><code> \<br>
-sDEVICE=pdfwrite -c .setpdfwrite -f </code><em>source1.ps [more files]</em>
</blockquote>
<p>Currently, the operator just sets a minimum 3 MB vmthreshold to allow for
accumulating shared object data and to reduce the incidence of garbage
collection as a performance improvement. Additional settings may be added in the future.
</dl>
<dl>
<dt><code>.color_test</code> and <code>.color_test_all</code></dt>
<dd>These operators are used for the verification of device encode_color and
decode_color routines. They are for internal use only. Their function
can, and probably will, change as Artifex's requirements change.
<p>
<dd>Currently these operators loop through a set of possible values for the inputs
to the encode_color routine and then veify that the decode_color routines produce
values that match the input set to within a tolerance which is based upon the number
of bits used to encode a pixel. The operators also verify that if the device
is 'separable' then that the values produced by gx_default_encode_color and
gx_default_decode_color (the default encode/decode color handlers for a separable
device) are consistent to within the same tolerance.
</dl>
<h4><a name="Device"></a>Device operators</h4>
<dl>
<dt><code><device> copydevice <device></code>
<dd>Copies a device. The copy is writable and installable. The copy is
created in the current VM (local or global), usually local VM for executing
ordinary PostScript files.
</dl>
<dl>
<dt><code><devicename> finddevice <device></code>
<dd>Creates a default instance of a device specified by name. The instance
is created in global VM. If <code>finddevice</code> is called more than
once with the same device name, it creates the default instance the first
time, and returns the same instance thereafter.
</dl>
<dl>
<dt><code><devicename> findprotodevice <device></code>
<dd>Finds the prototype of a device specified by name. A prototype can be
used with <code>.getdeviceparams</code> or other parameter-reading
operators, but it is read-only and cannot be set with
<code>setdevice</code>: it must be copied first.
</dl>
<dl>
<dt><code><device> <x> <y> <width> <max_height> <alpha?> <std_depth|null> <string> .getbitsrect <height> <substring></code>
<dd>Reads a rectangle of rendered bits back from a device. This is only
guaranteed to be implemented for image devices (see below).
<code>alpha?</code> is 0 for no alpha, -1 for alpha first, 1 for alpha
last. <code>std_depth</code> is null for native pixels, number of bits
per component for a standard color space.
</dl>
<dl>
<dt><code><index> .getdevice <device></code>
<dd>Returns a device from the set of devices known to the system. The
first device is numbered 0. If the <code>index</code> is out of
range, a <code>rangecheck</code> error occurs.
This device is actually a prototype, not a directly usable device,
and is marked read-only; it cannot have its parameters changed or be
installed as the current device.
</dl>
<dl>
<dt><code>- .getdefaultdevice <device></code>
<dd>Returns the default device. This device is actually a prototype,
and is marked read-only; it cannot have its parameters changed or
be installed as the current device.
Use <code>copydevice</code> to obtain a workable device.
</dl>
<dl>
<dt><code><matrix> <width> <height> <palette> makeimagedevice <device></code>
<dd>Makes a new device that accumulates an image in memory. <code>
matrix</code> is the initial transformation matrix: it must be orthogonal
(that is, [a 0 0 b x y] or
[0 a b 0 x y]). <code>palette</code> is a
string of 2^<small><sup><b>N</b></sup></small> or
3 × 2^<small><sup><b>N</b></sup></small> elements,
specifying how the 2^<small><sup><b>N</b></sup></small> possible pixel
values will be interpreted. Each element is interpreted as a gray value,
or as RGB values, multiplied by 255. For example, if you want a monochrome
image for which 0=white and 1=black, the palette should be
<code><ff 00></code>; if you want a 3-bit deep image with
just the primary colors and their complements (ignoring the fact that 3-bit
images are not supported), the palette might be <code><000000 0000ff
00ff00 00ffff ff0000 ff00ff ffff00 ffffff></code>. At present, the
palette must contain exactly 2, 4, 16, or 256 entries, and must contain an
entry for black and an entry for white; if it contains any entries that
aren't black, white, or gray, it must contain at least the six primary
colors (red, green, blue, and their complements cyan, magenta, and yellow);
aside from this, its contents are arbitrary.
<p>
Alternatively, palette can be 16, 24, 32, or null (equivalent to 24).
These are interpreted as:
<blockquote><table cellpadding=0 cellspacing=0>
<tr valign=bottom>
<th valign=bottom align=left>Palette
<td>
<th valign=bottom align=left>Bits allocated per color
<tr> <td colspan=3><hr>
<tr valign=top> <td>16
<td>
<td>5 red, 6 green, 5 blue
<tr valign=top> <td>24
<td>
<td>8 red, 8 green, 8 blue
<tr valign=top> <td>32
<td>
<td>8C, 8M, 8Y, 8K
</table></blockquote>
<p>
Note that one can also make an image device (with the same palette as an
existing image device) by copying a device using the
<code>copydevice</code> operator.
</dl>
<dl>
<dt><code><matrix> <width> <height> <palette> <word?> makewordimagedevice <device></code>
<dd>Makes an image device as described above. <code>word?</code> is a
Boolean value indicating whether the data should be stored in a
word-oriented format internally. No ordinary PostScript programs should
use this operator.
</dl>
<dl>
<dt><code><device> <index> <string> copyscanlines <substring></code>
<dd>Copies one or more scan lines from an image device into a string,
starting at a given scan line in the image. The data is in the same format
as for the <code>image</code> operator. It is an error if the device is
not an image device or if the string is too small to hold at least one
complete scan line. Always copies an integral number of scan lines.
</dl>
<dl>
<dt><code><device> setdevice -</code>
<dd>
<p>
Sets the current device to the specified device. Also resets the
transformation and clipping path to the initial values for the device.
Signals an <code>invalidaccess</code> error if the device is a
prototype or if <a href="Language.htm#LockSafetyParams">.LockSafetyParams</a>
is true for the current device.
<p>
Some device properties may need to be set with <tt>putdeviceprops</tt> before
<code>setdevice</code> is called. For example, the pdfwrite device will try
to open its output file, causing an <tt>undefinedfilename</tt> error if
<code>OutputFile</code> hasn't been set to a valid filename. Another
method in such cases is to use the level 2 operator instead:
<code><< /OutputDevice /pdfwrite /OutputFile
(MyPDF.pdf) >> setpagedevice</code>.
</dl>
<dl>
<dt><code>- currentdevice <device></code>
<dd>Gets the current device from the graphics state.
</dl>
<dl>
<dt><code><device> getdeviceprops <mark> <name1> <value1> ... <namen> <valuen></code>
<dd>Gets the properties of a device. See the section on
<a href="#Device_parameters">device parameters</a> below for details.
</dl>
<dl>
<dt><code><mark> <name1> <value1> ... <namen> <valuen> <device> putdeviceprops <device></code>
<dd>Sets properties of a device. May cause <code>undefined</code>,
<code>invalidaccess</code>, <code>typecheck</code>, <code>rangecheck</code>, or
<code>limitcheck</code> errors.
</dl>
<dl>
<dt><code>- flushpage -</code>
<dd>On displays, flushes any buffered output, so that it is guaranteed to
show up on the screen; on printers, has no effect.
</dl>
<hr>
<h2><a name="Filters"></a>Filters</h2>
<h3><a name="Standard_filters"></a>Standard filters</h3>
<p>
In its usual configuration, Ghostscript supports all the standard PostScript
LanguageLevel 3 filters, both encoding and decoding, except that it does not
currently support:
<ul>
<li>the <code>EarlyChange</code> key in the <code>LZWEncode</code>
filter.
</ul>
<p>
Ghostscript also supports additional keys in the optional dictionary
operands for some filters. For the <code>LZWDecode</code> filter:
<dl>
<dt><code>InitialCodeLength <integer></code> (default 8)
<dd>An integer between 2 and 11 specifying the initial number of data bits
per code. Note that the actual initial code length is 1 greater than this,
to allow for the reset and end-of-data code values.
</dl>
<dl>
<dt><code>FirstBitLowOrder <boolean></code> (default false)
<dd>If true, codes appear with their low-order bit first.
</dl>
<dl>
<dt><code>BlockData <boolean></code> (default false)
<dd>If true, the data is broken into blocks in the manner specified for the
GIF file format.
</dl>
<p>
For the <code>CCITTFaxEncode</code> and <code>CCITTFaxDecode</code>
filters:
<dl>
<dt><code>DecodedByteAlign <integer></code> (default 1)
<dd>An integer <b>N</b> with the value 1, 2, 4, 8, or 16, specifying that
decoded data scan lines are always a multiple of <b>N</b> bytes. The
encoding filter skips data in each scan line from Columns to the next
multiple of <b>N</b> bytes; the decoding filter pads each scan line to a
multiple of <b>N</b> bytes.
</dl>
<h3><a name="Non_standard_filters"></a>Non-standard filters</h3>
<p>
In addition to the standard PostScript LanguageLevel 3 filters, Ghostscript
supports the following non-standard filters. Many of these filters are used
internally to implement standard filters or facilities; they are almost
certain to remain, in their present form or a backward-compatible one, in
future Ghostscript releases.
<dl>
<dt><code><target> /BCPEncode filter <file></code>
<dt><code><source> /BCPDecode filter <file></code>
<dd>Create filters that implement the Adobe Binary Communications Protocol.
See Adobe documentation for details.
</dl>
<dl>
<dt><code><target> <seed_integer> /eexecEncode filter <file></code>
<dd>Creates a filter for encrypting data into the encrypted format described
in the Adobe Type 1 Font Format documentation. The
<code>seed_integer</code> must be 55665 for the <code>eexec</code>
section of a font, or 4330 for a <code>CharString</code>. Note that for
the <code>eexec</code> section of a font, this filter produces binary
output and does not include the initial 4 (or <code>lenIV</code>) garbage
bytes.
</dl>
<dl>
<dt><code><source> <seed_integer> /eexecDecode filter <file></code>
<dt><code><source> <dict> /eexecDecode filter <file></code>
<dd>Creates a filter for decrypting data encrypted as described in the Adobe
Type 1 Font Format documentation. The <code>seed_integer</code> must be
55665 or 4330 as described just above. PDF interpreters don't skip space characters
after operator <code>eexec</code>. Use <code>keep_spaces = true</code> for
decoding embedded PDF fonts. Recognized dictionary keys are:
<blockquote>
<code>seed <16-bit integer></code> (required)<br>
<code>lenIV <non-negative integer></code> (default=4)<br>
<code>eexec <bool></code> (default=<code>false</code>)<br>
<code>keep_spaces <bool></code> (default=<code>false</code>)
</blockquote>
</dl>
<dl>
<dt><code><target> /MD5Encode filter <file></code>
<dd>Creates a filter that produces the 16-byte MD5 digest of the input.
Note that no output is produced until the filter is closed.
</dl>
<dl>
<dt><code><source> <hex_boolean> /PFBDecode filter <file></code>
<dd>Creates a filter that decodes data in <code>.PFB</code> format, the
usual semi-binary representation for Type 1 font files on IBM PC and
compatible systems. If <code>hex_boolean</code> is true, binary packets
are converted to hex; if false, binary packets are not converted.
</dl>
<dl>
<dt><code><target> <dict> /PixelDifferenceEncode filter <file></code>
<dt><code><source> <dict> /PixelDifferenceDecode filter <file></code>
<dd>Implements the Predictor=2 pixel-differencing option of the LZW
filters. Recognized keys are:
<blockquote>
<code>Colors <integer></code> (1 to 4, default=1)<br>
<code>BitsPerComponent <integer></code> (1, 2, 4, or 8, default=8)<br>
<code>Columns <integer></code> (>= 0, required)
</blockquote>
<p>
See the Adobe <a href="http://partners.adobe.com/public/developer/pdf/index_reference.html"><em>PDF Reference Manual</em></a> for details.
</dl>
<dl>
<dt><code><target> <dict> /PNGPredictorEncode filter <file></code>
<dt><code><source> <dict> /PNGPredictorDecode filter <file></code>
<dd>Implements the "filter" algorithms of the
<a href="http://www.libpng.org/pub/png/">Portable Network Graphics (PNG)
graphics format</a>. Recognized keys are:
<blockquote><table cellpadding=0 cellspacing=0>
<tr><th colspan=5 bgcolor="#CCCC00"><hr><font size="+1">Keys recognized in PNG filter algorithms</font><hr>
<tr valign=bottom>
<th align=left>Key
<td>
<th align=left>Range
<td>
<th align=left>Default
<tr> <td colspan=5><hr>
<tr valign=top> <td><code>Colors <integer></code>
<td>
<td>1 to 16
<td>
<td>16
<tr valign=top> <td><code>BitsPerComponent <integer></code>
<td>
<td>1, 2, 4, 8, or 16
<td>
<td>8
<tr valign=top> <td><code>Columns <integer></code>
<td>
<td>>= 0
<td>
<td>1
<tr valign=top> <td><code>Predictor <integer></code>
<td>
<td>10 to 15
<td>
<td>15
</table></blockquote>
<p>
The <code>Predictor</code> is the PNG algorithm number + 10 for the
<code>Encoding</code> filter; the <code>Decoding</code> filter
ignores <code>Predictor</code>. 15 means the encoder attempts to
optimize the choice of algorithm. For more details see the PNG
specification
<blockquote>
<a href="http://www.w3.org/TR/WD-png-960128.html">http://www.w3.org/TR/WD-png-960128.html</a>
</blockquote>
</dl>
<dl>
<dt><code><target> /TBCPEncode filter <file></code>
<dt><code><source> /TBCPDecode filter <file></code>
<dd>Create filters that implement the Adobe Tagged Binary Communications
Protocol. See Adobe documentation for details.
</dl>
<dl>
<dt><code><target> /zlibEncode filter <file></code>
<dt><code><source> /zlibDecode filter <file></code>
<dd>Creates filters that use the data compression method variously known as
'zlib' (the name of a popular library that implements it), 'Deflate' (as in
<a href="http://www.ietf.org/rfc/rfc1951.txt">RFC 1951</a>, which is a
detailed specification for the method), 'gzip' (the name of a popular
compression application that uses it), or 'Flate' (Adobe's name). Note that
the PostScript <code>Flate</code> filters are actually a combination of
this filter with an optional predictor filter.
</dl>
<h3><a name="Unstable_filters"></a>Unstable filters</h3>
<p>
Some versions of Ghostscript may also support other non-standard filters for
experimental purposes. The current version includes the following such
filters, which are not documented further. No code should assume that these
filters will exist in compatible form, or at all, in future versions.
<dl>
<dt><code><target/source> <string> ByteTranslateEncode/Decode filter <file></code>
<dd><code>string</code> must be a string of exactly 256 bytes. Creates a
filter that converts each input byte <em>b</em> to
<code>string</code>[<em>b</em>]. Note that the <code>Encode</code>
and <code>Decode</code> filters operate identically: the client must
provide a <code>string</code> for the <code>Decode</code> filter that
is the inverse mapping of the <code>string</code> for the
<code>Encode</code> filter.
</dl>
<dl>
<dt><code><target/source> <dict> BoundedHuffmanEncode/Decode filter <file></code>
<dd>These filters encode and decode data using Huffman codes. Since these
filters aren't used anywhere, we don't document them further, except to note
the recognized dictionary keys, which must be set identically for encoding
and decoding:
<blockquote>
<code>FirstBitLowOrder <bool></code> (default=false)<br>
<code>MaxCodeLength <int></code> (default=16)<br>
<code>EndOfData <bool></code> (default=true)<br>
<code>EncodeZeroRuns <int></code> (default=256)<br>
<code>Tables <int_array></code>
</blockquote>
</dl>
<dl>
<dt><code><target/source> <dict> BWBlockSortEncode/Decode filter <file></code>
<dd>This filter implements the Burroughs-Wheeler block sorting compression
method, which we've heard is also used in the popular <code>bzip2</code>
compression application. See <a
href="http://sources.redhat.com/bzip2/">http://sources.redhat.com/bzip2/</a>
for more information. The only recognized dictionary key is:
<blockquote>
<code>BlockSize <integer></code> (default=16384)
</blockquote>
</dl>
<dl>
<dt><code><target/source> MoveToFrontEncode/Decode filter <file></code>
<dd>The <code>Encode</code> filter starts by initializing an internal
256-byte array <code>a</code> to the values 0 .. 255. This array will
always hold a permutation of these values. Then for each input byte
<em>b</em>, the filter outputs the index <em>i</em> such that
<code>a</code>[<em>i</em>] = <em>b</em>, and moves that element to the
front (element 0) of <code>a</code>, moving elements 0 .. <em>i-1</em> to
positions 1 .. <em>i</em>. The <code>Decode</code> filter inverts this
process.
</dl>
<hr>
<h2><a name="Device_parameters"></a>Device parameters</h2>
Ghostscript supports the concept of device parameters for all devices, not
just page devices. (For non-page devices, these are accessible through
<code>getdeviceprops</code> and <code>putdeviceprops</code>, as
indicated above.) Here are the currently defined parameters for all
devices:
<dl>
<dt><a name="LockSafetyParams"></a>
<code>.LockSafetyParams <boolean></code>
<dd>This parameter allows for improved system security by preventing
PostScript programs from being able to change potentially dangerous
device paramters such as OutputFile. This parameter cannot be set false
if it is already true.
<p>
If this parameter is true for the current device, attempt to set a new
device that has <code>.LockSafetyParams</code> false will signal an
<code> invalidaccess</code> error.
</dl>
<dl>
<dt><code>BitsPerPixel <integer> (usually read-only)</code>
<dd>Number of bits per pixel.
</dl>
<dl>
<dt><code>.HWMargins [<four floats>]</code>
<dd>Size of non-imageable regions around the edges of the page, in points
(units of 1/72in; see the <a href="Devices.htm#Measurements">notes on
measurements</a> in the documentation on devices).
</dl>
<dl>
<dt><code>HWSize [<integer> <integer>]</code>
<dd>X and Y size in pixels.
</dl>
<dl>
<dt><code>%MediaSource <integer></code>
<dd>The input tray key as determined by setpagedevice. PostScript
language programs don't set this parameter directly; they can
<em>request</em> a particular tray through the MediaPosition
setpagedevice parameter, but the setpagedevice logic need not
necessarily honor the request. Devices which support switchable trays
should implement %MediaSource in their put_params device procedure,
but (unlike most other such parameters) need not implement
corresponding reading logic in get_params.
</dl>
<dl>
<dt><code>%MediaDestination <integer></code>
<dd>The output tray key as determined by setpagedevice. Handling by
devices should be parallel to %MediaSource.
</dl>
<dl>
<dt><code>.IgnoreNumCopies <boolean></code>
<dd>Some page description languages support a NumCopies parameter.
This parameter instructs the device to ignore this, producing only
one copy of the document on output. Note that some devices ignore
NumCopies regardless because of limitation of the output format
or the implementation.
</dl>
<dl>
<dt><code>Name <string> (read-only)</code>
<dd>The device name. Currently the same as <code>OutputDevice</code>.
</dl>
<dl>
<dt><code>Colors, GrayValues, RedValues, GreenValues, BlueValues, ColorValues (usually read-only)</code>
<dd>As for the <code>deviceinfo</code> operator of Display PostScript.
<code>Red</code>, <code>Green</code>, <code>Blue</code>, and
<code>ColorValues</code> are only defined if
<code>Colors</code> > 1.
</dl>
<dl>
<dt><code>TextAlphaBits, GraphicsAlphaBits (usually read-only)</code>
<dd>The number of bits of anti-aliasing information for text or graphics
respectively. Legal values are 1 (no anti-aliasing, the default for most
devices), 2, or 4.
</dl>
<p>
Ghostscript also supports the following read-only parameter that is not a
true device parameter:
<dl>
<dt><code>.EmbedFontObjects <integer></code>
<dd>If non-zero, indicates that the device may embed font objects (as
opposed to bitmaps for individual characters) in the output. The purpose of
this parameter is to disable third-party font renderers for such devices.
(This is zero for almost all devices.)
</dl>
<p>
In addition, the following are defined per Adobe's documentation for the
<code>setpagedevice</code> operator:
<blockquote>
<code>Duplex</code> (if supported)<br>
<code>HWResolution</code><br>
<code>ImagingBBox</code><br>
<code>Margins</code><br>
<code>LeadingEdge</code><br>
<code>MediaPosition</code><br>
<code>NumCopies</code> (for printers only)<br>
<code>Orientation</code> (if supported)<br>
<code>OutputDevice</code><br>
<code>PageOffset</code> (write-only)<br>
<code>PageSize</code><br>
<code>ProcessColorModel</code> (usually read-only)<br>
</blockquote>
<p>
Some devices may only allow certain values for <code>HWResolution</code>
and <code>PageSize</code>. The null device ignores attempts to set
<code>PageSize</code>; its size is always <code>[0 0]</code>.
<p>
It should be noted that calling <tt>setpagedevice</tt> with one of the above keys may reset the effects of any <code>pdfmark</code> commands up to that point. In particular this is true of HWResolution, a behavior that differs from Adobe Distiller.
<a name="Banding_parameters"></a>
<p><b>
For raster printers and image format (jpeg*, tiff*, png* ...) devices these
page device parameters are also defined:</b>
<dl>
<dt><code>MaxBitmap <integer></code>
<dd>Maximum space for a full page raster image (bitmap) in memory.
<p>This value includes the space for padding raster lines and for an array of
pointers for each raster line, thus the <code>MaxBitmap</code> value to allow
a given PageSize of a specific number of bits per pixel to be rendered in a
full page buffer may be somewhat larger than the bitmap size alone.
</dl>
<dl>
<dt><code>BandListStorage <file|memory></code>
<dd>The default is determined by the make file macro <code>BAND_LIST_STORAGE</code>.
Since <code>memory</code> is always included, specifying <code>-sBandListStorage=memory</code>
when the default is <code>file</code> will use memory based storage for the
band list of the page. This is primarily intended for testing, but if the disk I/O is
slow, band list storage in memory may be faster.
</dl>
<dl>
<dt><code>BufferSpace <integer></code>
<dd>Size of the buffer space for band lists, if the full page raster image
(bitmap) is larger than <code>MaxBitmap</code> (see above.)
<p>The buffer space is used to collect display list (clist) commands for the
bands and then to consolidate those commands when writing the clist to the
selected BAND_LIST_STORAGE device (memory or file) set when Ghostscript is compiled.
<p>If <code>MaxBitmap</code> (above) forces banding mode, and if <code>BufferSpace</code>
is large enough, the display list (clist) will consist of a single band.
<p>The <code>BufferSpace</code> will determine the size of the 'consolidation'
buffer (above) even if the <code>MaxBitmap</code> value is low enough to force
banding/clist mode.
</dl>
<dl>
<dt><code>NumRenderingThreads <integer></code>
<dd>When the display list (clist) banding mode is being used, bands can be rendered
in separate threads. The default value, 0, causes the rendering of bands to be
done in the same thread as the parser and device driver. <code>NumRenderingThreads</code>
of 1 or higher results in bands rendering in the specified number of 'background'
threads.
<p>The number of threads should generally be set to the number of available
processor cores for best throughput.
<p>Note that each thread will allocate a band buffer (size determined by the
<code>BufferSpace</code> or <code>BandBufferSpace</code> values) in addition to
the band buffer in the 'main' thread.
</dl>
<dl>
<dt><code>OutputFile <string></code>
<dd>An empty string means "send to printer directly", otherwise specifies
the file name for output; <code>%d</code> is replaced by the page number
for page-oriented output devices;
on Unix systems <code>%pipe%</code><em>command</em> writes to a pipe.
(<code>|</code><em>command</em> also writes to a pipe, but is now
deprecated). Also see the <code>-o</code> parameter.
<p>
Attempts to set this parameter if <code>.LockSafetyParams</code> is true
will signal an <code>invalidaccess</code> error.
</dl>
<dl>
<dt><code>OpenOutputFile <boolean></code>
<dd>If true, open the device's output file when the device is opened,
rather than waiting until the first page is ready to print.
</dl>
<dl>
<dt><code>PageCount <integer> (read-only)</code>
<dd>Counts the number of pages printed on the device.
</dl>
<p>
The following parameters are for use only by very specialized applications
that separate band construction from band rasterization. <b>Improper use may
cause unpredictable errors.</b> In particular, if you only want to allocate
more memory for banding, to increase band size and improve performance, use
the <code>BufferSpace</code> parameter, not <code>BandBufferSpace</code>.
<dl>
<dt><code>BandHeight <integer></code>
<dd>The height of bands when banding. 0 means use the largest band height
that will fit within the <code>BandBufferSpace</code> (or <code>BufferSpace</code>,
if <code>BandBufferSpace</code> is not specified). If <code>BandHeight</code>
is larger than the number of lines that will fit in the buffer, opening the device will fail.
</dl>
<dl>
<dt><code>BandWidth <integer></code>
<dd>The width of bands in the rasterizing pass, in pixels. 0 means use the
actual page width. A BandWidth value smaller than the width of the page
will be ignored, and the actual page width will be used instead.
</dl>
<dl>
<dt><code>BandBufferSpace <integer></code>
<dd>The size of the band buffer in the rasterizing pass, in bytes. 0 means
use the same buffer size as for the interpretation pass.
</dl>
<p>
Ghostscript supports the following parameter for
<code>setpagedevice</code> and <code>currentpagedevice</code> that is
not a device parameter per se:
<dl>
<dt><code>ViewerPreProcess <procedure></code>
<dd>Specifies a procedure to be applied to the page device dictionary
before any other processing is done. The procedure may not alter the
dictionary, but it may return a modified copy. This "hook" is provided for
use by viewing programs such as GSview.
</dl>
<hr>
<h2><a name="User_parameters"></a>User parameters</h2>
Ghostscript supports the following non-standard user parameters:
<dl>
<dt><code>ProcessDSCComment <procedure|null></code>
<dd>If not null, this procedure is called whenever the scanner detects a DSC
comment (comment beginning with <code>%%</code> or <code>%!</code>).
There are two operands, the file and the comment (minus any terminating
EOL), which the procedure must consume.
</dl>
<dl>
<dt><code>ProcessComment <procedure|null></code>
<dd>If not null, this procedure is called whenever the scanner detects a
comment (or, if <code>ProcessDSCComment</code> is also not null, a
comment other than a DSC comment). The operands are the same as for
<code>ProcessDSCComment</code>.
</dl>
<dl>
<dt><code>LockFilePermissions <boolean></code>
<dd>If <tt>true</tt>, this parameter and the three <tt>PermitFile...</tt>
parameters cannot be changed. Attempts to change any of the values
when LockFilePermissions is <tt>true</tt> will signal <code>invalidaccess</code>.
Also, when this value is <tt>true</tt>, the <code>file</code> operator
will give <code>invalidaccess</code> when attempting to open files
(processes) using the <code>%pipe</code> device.
<p>
Also when <code>LockFilePermissions</code> is <tt>true</tt>, strings
cannot reference the parent directory (platform specific). For example
<code>(../../xyz)</code> is illegal on unix, Windows
and Macintosh, and <code>([.#.#.XYZ])</code> is illegal on VMS.
<p>
This parameter is set <tt>true</tt> by the <code>.setsafe</code> and
<code>.locksafe</code> operators.
</dl>
<dl>
<dt><code>PermitFileReading <array of strings></code>
<dt><code>PermitFileWriting <array of strings></code>
<dt><code>PermitFileControl <array of strings></code>
<dd>These parameters specify paths where file reading, writing and the
'control' operations are permitted, respectively. File control
operations are <code>deletefile</code> and <code>renamefile</code>.
For <code>renamefile</code>, the filename for the current filename
must match one of the paths on the PermitFileControl list, and the
new filename must be on <b>both</b> the PermitFileControl and the
PermitFileWriting lists of paths.
<p>
The strings can contain wildcard characters as for the <code>filenameforall</code>
operator and unless specifying a single file, will end with a <b>*</b>
for directories (folders) to allow access to all files and sub-directories
in that directory.
<p>
<b>Note:</b> The strings are used for stringmatch operations similar
to <code>filenameforall</code>, thus on MS Windows platforms, use the '/'
character to separate directories and filenames or use '\\\\' to
have the string contain '\\' which will match a single '\' in the
target filename (use of '/' is strongly recommended).
<p>
The <a href="Use.htm#Safer"><b>SAFER</b></a> mode and the
<code>.setsafe</code> operator set all three lists to empty arrays,
thus the only files that can be read are the <code>%stdin</code> device and
on LIBPATH or FONTPATH or the Resource paths specified by the /FontResourceDir
or /GenericResourceDir system params. Files cannot be opened for writing
anywhere and cannot be deleted or renamed except for files created with the
<a href="#Tempfile"><b>.tempfile</b></a> operator).
<p>
<b>Note: </b>Limiting file reading as above is <b>NOT</b> compatible with
SAFER mode in release versions before 7.11 and corresponds to the use of
<code>-dPARANOIDSAFER</code> in version 7.04 (up to and not including
version 7.10) and GPL versions 6.53 (up to and not including 6.60).
</dl>
<dl>
<dt><code>AlignToPixels <integer></code>
<dd>Control sub-pixel positioning of character glyphs (where
applicable). A value of 1 specifies alignment of text characters to
pixels boundaries. A value of 0 to subpixels where the division factor
is set by the device parameter <code>TextAlphaBits</code>. If the
latter is 1, the same rendering results regardless of the value of
<code>AlignToPixels</code>. The initial value defaults to 1, but this
may be overridden by the command line argument
<code>-dAlignToPixels</code>.
</dl>
<dl>
<dt><a name="GridFitTT"></a>
<code>GridFitTT <integer></code>
<dd>Control the use of True Type grid fitting.
Ghostscript implements a reduced True Type bytecode interpreter,
which can interpret the subset of True Type glyph instructions
not covered by Apple's patents. This allows proper rasterization
of the Dynalab fonts.
<p>
The reduced interpreter can't properly grid fit
fonts with patented instructions. Therefore Ghostscript implements
another grid fitting method for True Type fonts, based on a spot topology analysis.
<p>
This parameter controls the action of the reduced interpreter and the grid fitter:
<ul>
<li>
A value of 0 disables grid fitting for all True Type fonts. This is a backward compatibility mode.
</li>
<li>
A value of 1 enables the grid fitting for glyphs that don't involve
patented instructions, using the reduced True Type bytecode interpreter.
When a patented instruction is encountered, a warning is printed to stderr,
and the glyph is rendered ignoring the entire grid fitting program.
</li>
<li>
A value of 2 invokes the topological grid fitter. This value is recommended
for common use.
</li>
<li>
A value of 3 specifies that the bytecode interpreter to be used
to grid fit glyphs that have no patented instructions,
and other glyphs are grid fitted topologically. This mode may
improve the rendering of some fonts, but in general the best result
is not guaranteed.
</li>
</ul>
<p>
This parameter defaults to 2, but this
may be overridden on the command line with
<code>-dGridFitTT=n</code>.
<p>
The reduced bytecode interpreter is based in part of the work of the
<a href="http://freetype.org/">FreeType</a> Team.
The topological grid fitting is a new original Ghostscript method.
</dl>
<hr>
<h2><a name="Miscellaneous_additions"></a>Miscellaneous additions</h2>
<h3><a name="Extended_semantics_of_run"></a>Extended semantics of 'run'</h3>
<p>
The operator <code>run</code> can take either a string or a file as its argument. In
the latter case, it just runs the file, closing it at the end, and trapping
errors just as for the string case.
<h3><a name="DecodingResources"></a>Decoding resources</h3>
<p>
<code>Decoding</code> is a Ghostscript-specific resource category. It contains
various resources for emulating PostScript fonts with other font technologies.
Instances of the <tt>Decoding</tt> category are tables which map PostScript glyph
names to character codes used with TrueType, Intellifont, Microtype and other font formats.
<p>
Currently Ghostscript is capable of PostScript font emulation in 2 ways :
<ul>
<li>
1. Through <a href="./Use.htm#FAPI_run">FAPI</a> plugins, and
</li>
<li>
2. With TrueType font files, using the native font renderer, by
specifying TrueType font names or files in <a href="../lib/Fontmap">lib/Fontmap</a>.
</li>
</ul>
<p>
<code>Decoding</code> resources are not currently used by the native font renderer.
<p>
An instance of the <code>Decoding</code> resource category is
a dictionary. The dictionary keys are PostScript glyph names and the
values are either character codes, or arrays of character codes.
Arrays are used when a single name may be mapped to various character codes -
in this case Ghostscript tries all alternatives until a success.
The name of the resource instance should
reflect the character set for which it maps. For example,
<code>/Unicode</code> <code>/Decoding</code> resource maps to
Unicode UTF-16.
<p>
The rules for using <code>Decoding</code> resources in particular
cases are specified in the configuration file
<a href="../lib/xlatmap">lib/xlatmap</a>. See the file itself for more
information.
<p>
The file format for <code>Decoding</code> resource files is
generic PostScript.
Users may want to define custom <code>Decoding</code> resources.
The <code>ParseDecoding</code> procset defined in
<a href="../Resource/Init/gs_ciddc.ps">Resource/Init/gs_ciddc.ps</a> allows representation
of the table in a comfortable form.
<h3><a name="CIDDecodingResources"></a>CIDDecoding resources</h3>
<p>
<code>CIDDecoding</code> resources are similar to <code>Decoding</code>
resources, except they map Character Identifiers (CIDs) rather than glyph names.
Another difference is that the native Ghostscript font renderer uses
<code>CIDDecoding</code> resources while emulate CID fonts with TrueType or OpenType fonts.
<p>
An instance of the <code>CIDDecoding</code> resource category is
a dictionary of arrays. Keys in the dictionary are integers,
which correspond to high order byte of a CID.
Values are 256-element arrays, and their indices correspond to the low order byte of a CID.
Each elemet of an array is either null, or character code (integer), or an array
of character codes (integers). The zero code represents mapping to the default character.
<p>
The dictionary includes the additional key <code>CIDCount</code>.
Its value is the maximal CID defined, plus one.
<p>
The Ghostscript library is capable of generating some <code>CIDDecoding</code>
instances automatically, using the appropriate <code>CMap</code> (character map)
resources. This covers most of practical cases if the neccessary <code>CMap</code>
resources are provided. See the table <code>.CMapChooser</code> in
<a href="../Resource/Init/gs_ciddc.ps">Resource/Init/gs_ciddc.ps</a>
for the names of automatically gerenated resources and associated <code>CMap</code>s.
They allow to mapping CNS1, GB1, Japan1, Japan2 and Korea1 CID sets to TrueType
character sets known as Unicode (exactly UTF-16), Big5,
GB1213, ShiftJIS, Johab and Wansung.
<p>
The file format for <code>CIDDecoding</code> resource file is
generic PostScript.
Users may want to define custom resources to <code>CIDDecoding</code>
resource category.
<h3><a name="GlyphNames2Unicode"></a>GlyphNames2Unicode</h3>
<p>
<code>GlyphNames2Unicode</code> is an undocumented dictionary which Adobe
PostScript printer driver uses to communicate with Adobe Distiller.
In this dictionary the keys are glyph names, the values are Unicode UTF-16 codes for them.
The dictionaly is stored in the <code>FontInfo</code> dictionary under
the key <code>GlyphNames2Unicode</code>. Ghostscript recognises it and uses
to generate <code>ToUnicode</code> CMaps with pdfwrite.
<p>
<h3><a name="MultipleResourceDirectories"></a>Multiple Resource directories</h3>
<p>
Since 8.10 release Ghostscript maintains multiple resource directories.
<p>
Ghostscript does not distinguish <code>lib</code> and
<code>Resource</code> directories.
There is no file name conflicts because <code>lib</code> does not
contain subdirectories, but <code>Resource</code>
always store files in subdirectories.
<p>
The search method with multiple resource directories
appears not fully conforming to PLRM. We cannot unconditionally call
<code>ResourceFileName</code> while executing <code>findresource</code>
or <code>resourcestatus</code>, <code>resourceforall</code>, because
per PLRM it always returns a single path. Therefore Ghostscript
implements an extended search method in <code>findresource</code>,
<code>resourcestatus</code> and <code>resourceforall</code>, which
first calls <code>ResourceFileName</code> and checks whether the
returned path points to an existing file. If yes, the file is used,
othervise Ghostscript searches all directories specified in
<code>LIB_PATH</code>. With a single resource directory
it appears conforming to PLRM and equivalent to Adobe implementations.
<p>
<code>ResourceFileName</code> may be used for obtaining a path
where a resource file to be installed. In this case
Ghostscript to be invoked with <code>-sGenericResourceDir=path</code>,
specifying an absolute path. The default value for
<code>GenericResourceDir</code> is a relative path. Therefore
a default invocation with a PostScript installer
will install resource files into <code>/gs/Resource</code>.
<p>
<!-- [2.0 end contents] ==================================================== -->
<!-- [3.0 begin visible trailer] =========================================== -->
<hr>
<p>
<small>Copyright © 2000-2006 Artifex Software, Inc. All rights reserved.</small>
<p>
This software is provided AS-IS with no warranty, either express or
implied.
This software is distributed under license and may not be copied, modified
or distributed except as expressly authorized under the terms of that
license. Refer to licensing information at http://www.artifex.com/
or contact Artifex Software, Inc., 7 Mt. Lassen Drive - Suite A-134,
San Rafael, CA 94903, U.S.A., +1(415)492-9861, for further information.
<p>
<small>Ghostscript version 9.06, 8 August 2012
<!-- [3.0 end visible trailer] ============================================= -->
</body>
</html>
|