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<page xmlns="http://projectmallard.org/1.0/"
type="topic"
id="ocrconfiguration">
<info>
<link type="guide" xref="index#configuration"/>
<link type="seealso" xref="automaticrecognition"/>
<link type="seealso" xref="manualeditionandcorrection"/>
<desc>Configure the OCR engines to recognize the text</desc>
</info>
<title>OCR Engines Configuration</title>
<p><app>OCRFeeder</app> uses system-wide OCR engines to extract
the text from images. This means any OCR engine that can be
used from the command line should also be used in <app>OCRFeeder</app>.</p>
<section id="automatic">
<title>Automatic Detection of OCR Engines</title>
<p>The OCR engines (<em>Tesseract</em>, <em>GOCR</em>, <em>Ocrad</em>
and <em>Cuneiform</em>) are already automatically detected and configured
in most systems, the first time <app>OCRFeeder</app> is run.</p>
<p>If an OCR engine is installed after <app>OCRFeeder</app> had configured
already an engine, it will not be automatically configured but, depending on
the engine, users might easily go to the <gui>OCR Engines</gui> dialog and
choose it from the list of detected engines after pressing <gui>Detect</gui>.</p>
<note style="tip"><p>Already configured OCR engines might be detected again and it is
up to the user to uncheck these engines if they shouldn't be added again.</p></note>
</section>
<section id="manual">
<title>Manual Configuration</title>
<p>The currently configured OCR engines are shown in the
<gui>OCR Engines</gui> dialog which can be opened from
<guiseq><gui>Tools</gui><gui>OCR Engines</gui></guiseq>.</p>
<p>Besides seeing the configured OCR engines, the <gui>OCR Engines</gui>
dialog allows to add new engines, edit or delete the current ones and
detect engines installed in the system.</p>
<p>When adding or editing an OCR engine (by pressing the <gui>Add</gui>
or <gui>Edit</gui> buttons, respectively), a dialog is shown with the
following fields:</p>
<list>
<item><p><gui>Name</gui>: The engine's name. This name will be used
in throughout the UI when referring to the engine;</p></item>
<item><p><gui>Image format</gui>: The image format that the engine
recognizes (for example, <em>TIF</em> in the case of
<em>Tesseract</em>);</p></item>
<item><p><gui>Failure string</gui>: Some engines replace unrecognized
characters by another, pre-defined character (for example,
<em>_</em> in the case of <em>GOCR</em>).</p></item>
<item><p><gui>Engine path</gui>: The path in the system to the
engine's executable (for example, <em>/usr/bin/tesseract</em>).</p></item>
<item><p><gui>Engine arguments</gui>: The arguments that feed an image
to the engine and make it output the recognized text to the standard
output. <app>OCRFeeder</app> runs the engine with these arguments
as if it was in the command line and looks for the recognized text
in the standard output. Some engines already do this, like
<em>Ocrad</em> and <em>GOCR</em> while other, like <em>Tesseract</em>,
write the text into a file.</p>
<p>Since the image's path to be read is always needed, a special argument
<em>$IMAGE</em> is provided for this and will be replaced by the image path
when the engine is run. For the cases
where a file name is needed, like the one mentioned previously, a special
argument <em>$FILE</em> is provided and will be replaced by a temporary
file name.</p>
<p>So, in case of <em>Tesseract</em> (which writes the recognized text
into a file), the arguments would be <em>$IMAGE $FILE; cat $FILE.txt;
rm $FILE</em>.</p></item>
</list>
<note style="advanced"><p>The engines' configuration is stored in their own XML file
in the user's home under <em>.config/ocrfeeder/engines/</em>.</p></note>
</section>
</page>
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