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DRC 9983840eb6 TJ/xform: Check crop region against dest. image 
Lossless cropping is performed after other lossless transform
operations, so the cropping region must be specified relative to the
destination image dimensions and level of chrominance subsampling, not
the source image dimensions and level of chrominance subsampling.

More specifically, if the lossless transform operation swaps the X and Y
axes, or if the image is converted to grayscale, then that changes the
cropping region requirements.
2024-08-31 15:04:30 -04:00

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<a href="#pub-attribs">Data Fields</a> </div>
<div class="headertitle"><div class="title">tjregion Struct Reference<div class="ingroups"><a class="el" href="group___turbo_j_p_e_g.html">TurboJPEG</a></div></div></div>
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<p>Cropping region.
<a href="structtjregion.html#details">More...</a></p>
<p><code>#include &lt;turbojpeg.h&gt;</code></p>
<table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a id="pub-attribs" name="pub-attribs"></a>
Data Fields</h2></td></tr>
<tr class="memitem:a4b6a37a93997091b26a75831fa291ad9" id="r_a4b6a37a93997091b26a75831fa291ad9"><td class="memItemLeft" align="right" valign="top">int&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structtjregion.html#a4b6a37a93997091b26a75831fa291ad9">x</a></td></tr>
<tr class="memdesc:a4b6a37a93997091b26a75831fa291ad9"><td class="mdescLeft">&#160;</td><td class="mdescRight">The left boundary of the cropping region. <br /></td></tr>
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<tr class="memitem:a7b3e0c24cfe87acc80e334cafdcf22c2" id="r_a7b3e0c24cfe87acc80e334cafdcf22c2"><td class="memItemLeft" align="right" valign="top">int&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structtjregion.html#a7b3e0c24cfe87acc80e334cafdcf22c2">y</a></td></tr>
<tr class="memdesc:a7b3e0c24cfe87acc80e334cafdcf22c2"><td class="mdescLeft">&#160;</td><td class="mdescRight">The upper boundary of the cropping region. <br /></td></tr>
<tr class="separator:a7b3e0c24cfe87acc80e334cafdcf22c2"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:ab6eb73ceef584fc23c8c8097926dce42" id="r_ab6eb73ceef584fc23c8c8097926dce42"><td class="memItemLeft" align="right" valign="top">int&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structtjregion.html#ab6eb73ceef584fc23c8c8097926dce42">w</a></td></tr>
<tr class="memdesc:ab6eb73ceef584fc23c8c8097926dce42"><td class="mdescLeft">&#160;</td><td class="mdescRight">The width of the cropping region. <br /></td></tr>
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<tr class="memitem:aecefc45a26f4d8b60dd4d825c1710115" id="r_aecefc45a26f4d8b60dd4d825c1710115"><td class="memItemLeft" align="right" valign="top">int&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="structtjregion.html#aecefc45a26f4d8b60dd4d825c1710115">h</a></td></tr>
<tr class="memdesc:aecefc45a26f4d8b60dd4d825c1710115"><td class="mdescLeft">&#160;</td><td class="mdescRight">The height of the cropping region. <br /></td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><p>Cropping region. </p>
</div><h2 class="groupheader">Field Documentation</h2>
<a id="aecefc45a26f4d8b60dd4d825c1710115" name="aecefc45a26f4d8b60dd4d825c1710115"></a>
<h2 class="memtitle"><span class="permalink"><a href="#aecefc45a26f4d8b60dd4d825c1710115">&#9670;&#160;</a></span>h</h2>
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<td class="memname">int tjregion::h</td>
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<p>The height of the cropping region. </p>
<p>Setting this to 0 is the equivalent of setting it to the height of the source JPEG image - y. </p>
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<h2 class="memtitle"><span class="permalink"><a href="#ab6eb73ceef584fc23c8c8097926dce42">&#9670;&#160;</a></span>w</h2>
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<p>The width of the cropping region. </p>
<p>Setting this to 0 is the equivalent of setting it to the width of the source JPEG image - x. </p>
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<h2 class="memtitle"><span class="permalink"><a href="#a4b6a37a93997091b26a75831fa291ad9">&#9670;&#160;</a></span>x</h2>
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<p>The left boundary of the cropping region. </p>
<p>For lossless transformation, this must be evenly divisible by the iMCU width (see <a class="el" href="group___turbo_j_p_e_g.html#ga9e61e7cd47a15a173283ba94e781308c" title="iMCU width (in pixels) for a given level of chrominance subsampling">tjMCUWidth</a>) of the destination image. For decompression, this must be evenly divisible by the scaled iMCU width of the source image. </p>
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<h2 class="memtitle"><span class="permalink"><a href="#a7b3e0c24cfe87acc80e334cafdcf22c2">&#9670;&#160;</a></span>y</h2>
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<td class="memname">int tjregion::y</td>
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<p>The upper boundary of the cropping region. </p>
<p>For lossless transformation, this must be evenly divisible by the iMCU height (see <a class="el" href="group___turbo_j_p_e_g.html#gabd247bb9fecb393eca57366feb8327bf" title="iMCU height (in pixels) for a given level of chrominance subsampling">tjMCUHeight</a>) of the destination image. </p>
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<hr/>The documentation for this struct was generated from the following file:<ul>
<li><b>turbojpeg.h</b></li>
</ul>
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