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5.3 KiB
HTML
120 lines
5.3 KiB
HTML
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<title>Basics - Boost.GIL documentation</title>
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<h3><a href="../index.html"><img
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alt="C++ Boost" src="../_static/gil.png" border="0"></a></h3>
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<div class="section" id="basics">
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<h1>Basics</h1>
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<p>Images are essential in any image processing, vision and video project, and
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yet the variability in image representations makes it difficult to write
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imaging algorithms that are both generic and efficient. In this section we
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will describe some of the challenges that we would like to address.</p>
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<p>In the following discussion an <em>image</em> is a 2D array of pixels. A <em>pixel</em> is a
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set of color channels that represents the color at a given point in an image.
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Each <em>channel</em> represents the value of a color component. There are two common
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memory structures for an image. <em>Interleaved</em> images are represented by
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grouping the pixels together in memory and interleaving all channels together,
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whereas <em>planar</em> images keep the channels in separate color planes. Here is a
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4x3 RGB image in which the second pixel of the first row is marked in red,
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in interleaved form:</p>
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<img alt="../_images/interleaved.jpg" src="../_images/interleaved.jpg" />
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<p>and in planar form:</p>
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<img alt="../_images/planar.jpg" src="../_images/planar.jpg" />
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<p>Note also that rows may optionally be aligned resulting in a potential padding
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at the end of rows.</p>
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<p>The Generic Image Library (GIL) provides models for images that vary in:</p>
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<ul class="simple">
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<li>Structure (planar vs. interleaved)</li>
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<li>Color space and presence of alpha (RGB, RGBA, CMYK, etc.)</li>
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<li>Channel depth (8-bit, 16-bit, etc.)</li>
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<li>Order of channels (RGB vs. BGR, etc.)</li>
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<li>Row alignment policy (no alignment, word-alignment, etc.)</li>
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</ul>
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<p>It also supports user-defined models of images, and images whose parameters
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are specified at run-time. GIL abstracts image representation from algorithms
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applied on images and allows us to write the algorithm once and have it work
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on any of the above image variations while generating code that is comparable
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in speed to that of hand-writing the algorithm for a specific image type.</p>
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<p>This document follows bottom-up design. Each section defines concepts that
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build on top of concepts defined in previous sections. It is recommended to
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read the sections in order.</p>
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<div class="footer" role="contentinfo">
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Last updated on 2021-04-13 16:04:40.
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Created using <a href="http://sphinx-doc.org/">Sphinx</a> 1.5.6.
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