/usr/share/pyshared/Eikazo/doc/postproc.html

<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="generator" content="Docutils 0.4: http://docutils.sourceforge.net/" />
<title></title>
<style type="text/css">

/*
:Author: David Goodger
:Contact: goodger@users.sourceforge.net
:Date: $Date: 2006/08/08 12:38:41 $
:Revision: $Revision: 1.1.1.1 $
:Copyright: This stylesheet has been placed in the public domain.

Default cascading style sheet for the HTML output of Docutils.

See http://docutils.sf.net/docs/howto/html-stylesheets.html for how to
customize this style sheet.
*/

/* used to remove borders from tables and images */
.borderless, table.borderless td, table.borderless th {
  border: 0 }

table.borderless td, table.borderless th {
  /* Override padding for "table.docutils td" with "! important".
     The right padding separates the table cells. */
  padding: 0 0.5em 0 0 ! important }

.first {
  /* Override more specific margin styles with "! important". */
  margin-top: 0 ! important }

.last, .with-subtitle {
  margin-bottom: 0 ! important }

.hidden {
  display: none }

a.toc-backref {
  text-decoration: none ;
  color: black }

blockquote.epigraph {
  margin: 2em 5em ; }

dl.docutils dd {
  margin-bottom: 0.5em }

/* Uncomment (and remove this text!) to get bold-faced definition list terms
dl.docutils dt {
  font-weight: bold }
*/

div.abstract {
  margin: 2em 5em }

div.abstract p.topic-title {
  font-weight: bold ;
  text-align: center }

div.admonition, div.attention, div.caution, div.danger, div.error,
div.hint, div.important, div.note, div.tip, div.warning {
  margin: 2em ;
  border: medium outset ;
  padding: 1em }

div.admonition p.admonition-title, div.hint p.admonition-title,
div.important p.admonition-title, div.note p.admonition-title,
div.tip p.admonition-title {
  font-weight: bold ;
  font-family: sans-serif }

div.attention p.admonition-title, div.caution p.admonition-title,
div.danger p.admonition-title, div.error p.admonition-title,
div.warning p.admonition-title {
  color: red ;
  font-weight: bold ;
  font-family: sans-serif }

/* Uncomment (and remove this text!) to get reduced vertical space in
   compound paragraphs.
div.compound .compound-first, div.compound .compound-middle {
  margin-bottom: 0.5em }

div.compound .compound-last, div.compound .compound-middle {
  margin-top: 0.5em }
*/

div.dedication {
  margin: 2em 5em ;
  text-align: center ;
  font-style: italic }

div.dedication p.topic-title {
  font-weight: bold ;
  font-style: normal }

div.figure {
  margin-left: 2em ;
  margin-right: 2em }

div.footer, div.header {
  clear: both;
  font-size: smaller }

div.line-block {
  display: block ;
  margin-top: 1em ;
  margin-bottom: 1em }

div.line-block div.line-block {
  margin-top: 0 ;
  margin-bottom: 0 ;
  margin-left: 1.5em }

div.sidebar {
  margin-left: 1em ;
  border: medium outset ;
  padding: 1em ;
  background-color: #ffffee ;
  width: 40% ;
  float: right ;
  clear: right }

div.sidebar p.rubric {
  font-family: sans-serif ;
  font-size: medium }

div.system-messages {
  margin: 5em }

div.system-messages h1 {
  color: red }

div.system-message {
  border: medium outset ;
  padding: 1em }

div.system-message p.system-message-title {
  color: red ;
  font-weight: bold }

div.topic {
  margin: 2em }

h1.section-subtitle, h2.section-subtitle, h3.section-subtitle,
h4.section-subtitle, h5.section-subtitle, h6.section-subtitle {
  margin-top: 0.4em }

h1.title {
  text-align: center }

h2.subtitle {
  text-align: center }

hr.docutils {
  width: 75% }

img.align-left {
  clear: left }

img.align-right {
  clear: right }

ol.simple, ul.simple {
  margin-bottom: 1em }

ol.arabic {
  list-style: decimal }

ol.loweralpha {
  list-style: lower-alpha }

ol.upperalpha {
  list-style: upper-alpha }

ol.lowerroman {
  list-style: lower-roman }

ol.upperroman {
  list-style: upper-roman }

p.attribution {
  text-align: right ;
  margin-left: 50% }

p.caption {
  font-style: italic }

p.credits {
  font-style: italic ;
  font-size: smaller }

p.label {
  white-space: nowrap }

p.rubric {
  font-weight: bold ;
  font-size: larger ;
  color: maroon ;
  text-align: center }

p.sidebar-title {
  font-family: sans-serif ;
  font-weight: bold ;
  font-size: larger }

p.sidebar-subtitle {
  font-family: sans-serif ;
  font-weight: bold }

p.topic-title {
  font-weight: bold }

pre.address {
  margin-bottom: 0 ;
  margin-top: 0 ;
  font-family: serif ;
  font-size: 100% }

pre.literal-block, pre.doctest-block {
  margin-left: 2em ;
  margin-right: 2em ;
  background-color: #eeeeee }

span.classifier {
  font-family: sans-serif ;
  font-style: oblique }

span.classifier-delimiter {
  font-family: sans-serif ;
  font-weight: bold }

span.interpreted {
  font-family: sans-serif }

span.option {
  white-space: nowrap }

span.pre {
  white-space: pre }

span.problematic {
  color: red }

span.section-subtitle {
  /* font-size relative to parent (h1..h6 element) */
  font-size: 80% }

table.citation {
  border-left: solid 1px gray;
  margin-left: 1px }

table.docinfo {
  margin: 2em 4em }

table.docutils {
  margin-top: 0.5em ;
  margin-bottom: 0.5em;
  border: 0 }

table.footnote {
  border-left: solid 1px black;
  margin-left: 1px }

table.docutils td, table.docutils th,
table.docinfo td, table.docinfo th {
  padding-left: 0.5em ;
  padding-right: 0.5em ;
  vertical-align: top ;
  border: 0}

table.docutils th.field-name, table.docinfo th.docinfo-name {
  font-weight: bold ;
  text-align: left ;
  white-space: nowrap ;
  padding-left: 0 }

h1 tt.docutils, h2 tt.docutils, h3 tt.docutils,
h4 tt.docutils, h5 tt.docutils, h6 tt.docutils {
  font-size: 100% }

tt.docutils {
  background-color: #eeeeee }

ul.auto-toc {
  list-style-type: none }

</style>
</head>
<body>
<div class="document">
<table border="1" class="docutils">
<colgroup>
<col width="37%" />
<col width="32%" />
<col width="32%" />
</colgroup>
<tbody valign="top">
<tr><td><a class="reference" href="scanjobs.html">prev: Scan Jobs</a></td>
<td><a class="reference" href="index.html">up: Contents</a></td>
<td><a class="reference" href="output.html">next: Output</a></td>
</tr>
</tbody>
</table>
<div class="section">
<h1><a id="postprocessing" name="postprocessing">Postprocessing</a></h1>
<p>At present, Eikazo provides three postprocessing options:</p>
<ul class="simple">
<li><a class="reference" href="#adaptive-threshold">Adaptive Threshold</a> filter</li>
<li><a class="reference" href="#clean">Clean</a> filter</li>
<li><a class="reference" href="#imagemagick">ImageMagick</a> filter</li>
</ul>
<p>All filter options can independently be enabled and disabled; they are
invoked in the same sequence as they are displayed in the postprocessing
tab.</p>
<p>Some filters do not process all image types; the adaptive threshold
filter for example works only on gray scale images. If
an unsupported image type is fed to such a filter, it returns the
image unchanged.</p>
<div class="section">
<h2><a id="adaptive-threshold" name="adaptive-threshold">Adaptive Threshold</a></h2>
<p>This filter converts gray scale images into lineart images. For each
pixel of the input image, it calculates the average value of the pixels
in a square area around this pixel. The threshold value for the center pixel
is this average minus an offset value. This allows reliable thresholding
even for documents with considerable changes of the background color.</p>
<div class="figure">
<img alt="images/postproc1.png" src="images/postproc1.png" />
<p class="caption">Adaptive Threshold tab</p>
</div>
<p>A drawback of the filter: If you have dark areas that are larger than
the averaging square, it can happen that only the edges of the area
will stay dark, and that the &quot;inner part&quot; of such an area will become
white. This occurs, if the offset value is too small. In this case you
can either increase the averaging square or increase the threshold value.</p>
<p>The runtime of the algorithm is proportional to O(n), where n is the
length of the averaging square, i.e., it is much faster for larger
squares than a universal convolution filter, whose runtime is often O(n*n).</p>
</div>
<div class="section">
<h2><a id="clean" name="clean">Clean</a></h2>
<p>This filter works only on lineart images.</p>
<p>For a &quot;noisy&quot; image, thresholding can lead to many small speckles
in the image. This can occur both for a simple constant threshold, as well
as for the adaptive threshold. The clean filter counts the number
of black pixels in a square area around each pixel; if this number
is below a selectable threshold, the center pixel becomes a white pixel.</p>
<div class="figure">
<img alt="images/postproc2.png" src="images/postproc2.png" />
<p class="caption">Adaptive Clean tab</p>
</div>
</div>
<div class="section">
<h2><a id="imagemagick" name="imagemagick">ImageMagick</a></h2>
<p>This plugin simply calls the program &quot;convert&quot; from
ImageMagick. It is mostly intended to be an example, that it is
quite simple to include an external program as a filter for Eikazo.
Including the lengthy copyright notice, the source code consists of only 126
lines. Its &quot;real&quot; usefulness for daily scan tasks is at least in its
current setup - only &quot;boolean&quot; options are supported - questionable.</p>
<p>Please note that convert may need considerable amounts of memory and may
run for a long time for some filter options.</p>
<div class="figure">
<img alt="images/postproc3.png" src="images/postproc3.png" />
<p class="caption">ImageMagick tab</p>
</div>
</div>
</div>
</div>
</body>
</html>
eikazo 0.5.2-8 / usr / share / pyshared / Eikazo / doc / postproc.html
