/usr/share/doc/libplplot11/examples/lua/x20.lua is in libplplot-dev 5.9.9-2ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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plimage demo
--]]
-- initialise Lua bindings for PLplot examples.
dofile("plplot_examples.lua")
XDIM = 260
YDIM = 220
dbg = 0
nosombrero = 0
nointeractive = 0
f_name=""
-- Transformation function
function mypltr(x, y)
local x0 = (stretch["xmin"] + stretch["xmax"])*0.5
local y0 = (stretch["ymin"] + stretch["ymax"])*0.5
local dy = (stretch["ymax"]-stretch["ymin"])*0.5
local tx = x0 + (x0-x)*(1 - stretch["stretch"]*math.cos((y-y0)/dy*math.pi*0.5))
local ty = y
return tx, ty
end
-- read image from file in binary ppm format
function read_img(fname)
-- naive grayscale binary ppm reading. If you know how to, improve it
local fp = io.open(fname, "rb")
if fp==nil then
return 1
end
-- version
local ver = fp:read("*line")
if ver~="P5" then -- I only understand this!
fp:close()
return 1
end
while fp:read(1)=="#" do
local com = fp:read("*line")
if com==nil then
fp:close()
return 1
end
end
fp:seek("cur", -1)
local w, h, num_col = fp:read("*number", "*number", "*number")
if w==nil or h==nil or num_col==nil then -- width, height, num colors
fp:close()
return 1
end
-- read the rest of the line (only EOL)
fp:read("*line")
local img = fp:read(w*h)
fp:close()
if string.len(img)~=(w*h) then
return 1
end
local imf = {}
for i = 1, w do
imf[i] = {}
for j = 1, h do
imf[i][j] = string.byte(img, (h-j)*w+i) -- flip image up-down
end
end
return 0, imf, w, h, num_col
end
-- save plot
function save_plot(fname)
local cur_strm = pl.gstrm() -- get current stream
local new_strm = pl.mkstrm() -- create a new one
pl.sdev("psc") -- new device type. Use a known existing driver
pl.sfnam(fname) -- file name
pl.cpstrm(cur_strm, 0) -- copy old stream parameters to new stream
pl.replot() -- do the save
pl.end1() -- close new device
pl.sstrm(cur_strm) -- and return to previous one
end
-- get selection square interactively
function get_clip(xi, xe, yi, ye)
return 0, xi, xe, yi, ye
end
-- set gray colormap
function gray_cmap(num_col)
local r = { 0, 1 }
local g = { 0, 1 }
local b = { 0, 1 }
local pos = { 0, 1 }
pl.scmap1n(num_col)
pl.scmap1l(1, pos, r, g, b)
end
x = {}
y = {}
z = {}
r = {}
img_f = {}
cgrid2 = {}
-- Bugs in plimage():
-- + at high magnifications, the left and right edge are ragged, try
-- ./x20c -dev xwin -wplt 0.3,0.3,0.6,0.6 -ori 0.5
-- Bugs in x20c.c:
-- + if the window is resized after a selection is made on "lena", when
--making a new selection the old one will re-appear.
-- Parse and process command line arguments
pl.parseopts(arg, pl.PL_PARSE_FULL)
-- Initialize plplot
pl.init()
z={}
-- view image border pixels
if dbg~=0 then
pl.env(1, XDIM, 1, YDIM, 1, 1) -- no plot box
-- build a one pixel square border, for diagnostics
for i = 1, XDIM do
z[i] = {}
z[i][1] = 1 -- left
z[i][YDIM] = 1 -- right
end
for i = 1, YDIM do
z[1][i] = 1 -- top
z[XDIM][i] = 1 -- botton
end
pl.lab("...around a blue square."," ","A red border should appear...")
pl.image(z, 1, XDIM, 1, YDIM, 0, 0, 1, XDIM, 1, YDIM)
end
-- sombrero-like demo
if nosombrero==0 then
r = {}
pl.col0(2) -- draw a yellow plot box, useful for diagnostics! :(
pl.env(0, 2*math.pi, 0, 3*math.pi, 1, -1)
for i = 1, XDIM do
x[i] = (i-1)*2*math.pi/(XDIM-1)
end
for i = 1, YDIM do
y[i] = (i-1)*3*math.pi/(YDIM-1)
end
for i = 1, XDIM do
r[i] = {}
z[i] = {}
for j=1, YDIM do
r[i][j] = math.sqrt(x[i]^2+y[j]^2)+1e-3
z[i][j] = math.sin(r[i][j])/r[i][j]
end
end
pl.lab("No, an amplitude clipped \"sombrero\"", "", "Saturn?")
pl.ptex(2, 2, 3, 4, 0, "Transparent image")
pl.image(z, 0, 2*math.pi, 0, 3*math.pi, 0.05, 1, 0, 2*math.pi, 0, 3*math.pi)
-- save the plot
if f_name~="" then
save_plot(f_name)
end
end
-- read Lena image
-- Note we try two different locations to cover the case where this
-- examples is being run from the test_c.sh script
status, img_f, width, height, num_col = read_img("lena.pgm")
if status~=0 then
status, img_f, width, height, num_col = read_img("../lena.pgm")
if status~=0 then
pl.abort("No such file")
pl.plend()
os.exit()
end
end
-- set gray colormap
gray_cmap(num_col)
-- display Lena
pl.env(1, width, 1, height, 1, -1)
if nointeractive==0 then
pl.lab("Set and drag Button 1 to (re)set selection, Button 2 to finish."," ","Lena...")
else
pl.lab(""," ","Lena...")
end
pl.image(img_f, 1, width, 1, height, 0, 0, 1, width, 1, height)
-- selection/expansion demo
if nointeractive==0 then
xi = 200
xe = 330
yi = 280
ye = 220
status, xi, xe, yi, ye = get_clip(xi, xe, yi, ye)
if status~=0 then -- get selection rectangle
pl.plend()
os.exit()
end
pl.spause(0)
pl.adv(0)
-- display selection only
pl.image(img_f, 1, width, 1, height, 0, 0, xi, xe, ye, yi)
pl.spause(1)
-- zoom in selection
pl.env(xi, xe, ye, yi, 1, -1)
pl.image(img_f, 1, width, 1, height, 0, 0, xi, xe, ye, yi)
end
-- Base the dynamic range on the image contents.
img_max, img_min = pl.MinMax2dGrid(img_f)
-- Draw a saturated version of the original image. Only use the middle 50%
-- of the image's full dynamic range.
pl.col0(2)
pl.env(0, width, 0, height, 1, -1)
pl.lab("", "", "Reduced dynamic range image example")
pl.imagefr(img_f, 0, width, 0, height, 0, 0, img_min + img_max*0.25, img_max - img_max*0.25)
-- Draw a distorted version of the original image, showing its full dynamic range.
pl.env(0, width, 0, height, 1, -1)
pl.lab("", "", "Distorted image example")
stretch = {}
stretch["xmin"] = 0
stretch["xmax"] = width
stretch["ymin"] = 0
stretch["ymax"] = height
stretch["stretch"] = 0.5
-- In C / C++ the following would work, with plimagefr directly calling
-- mypltr. For compatibilty with other language bindings the same effect
-- can be achieved by generating the transformed grid first and then
-- using pltr2.
-- pl.imagefr(img_f, width, height, 0., width, 0., height, 0., 0., img_min, img_max, mypltr, (PLPointer) &stretch)
cgrid2 = {}
cgrid2["xg"] = {}
cgrid2["yg"] = {}
cgrid2["nx"] = width+1
cgrid2["ny"] = height+1
for i = 1, width+1 do
cgrid2["xg"][i] = {}
cgrid2["yg"][i] = {}
for j = 1, height+1 do
xx, yy = mypltr(i, j)
cgrid2["xg"][i][j] = xx
cgrid2["yg"][i][j] = yy
end
end
--pl.imagefr(img_f, 0, width, 0, height, 0, 0, img_min, img_max, "pltr2", cgrid2)
pl.imagefr(img_f, 0, width, 0, height, 0, 0, img_min, img_max, "mypltr")
pl.plend()
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