wcslib (8.2.2)
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<div id="projectname">WCSLIB<span id="projectnumber"> 8.2.2</span>
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<li class="navelem"><a class="el" href="index.html">WCSLIB 8.2.2 and PGSBOX 8.2.2</a></li> </ul>
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<div class="headertitle"><div class="title">Limits</div></div>
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<div class="textblock"><p>While the FITS WCS standard imposes a limit of 99 on the number of image coordinate axes, WCSLIB has a limit of 32 on the number it can handle – enforced by <a class="el" href="wcs_8h.html#ae5cc3f5d249755583403cdf54d2ebb91" title="Setup routine for the wcsprm struct.">wcsset()</a>, though allowed by <a class="el" href="wcs_8h.html#aab11243b60b10065fc85347bb3efa912" title="Default constructor for the wcsprm struct.">wcsinit()</a>. This arises in <a class="el" href="wcs_8h.html#a27d3dd209db3e76cf4c50f48c01ba986" title="Pixel-to-world transformation.">wcsp2s()</a> and <a class="el" href="wcs_8h.html#a60673d05a3513659ac848a9cb3d0cb07" title="World-to-pixel transformation.">wcss2p()</a> from the use of the <em>stat[]</em> vector as a bit mask to indicate invalid pixel or world coordinate elements.</p>
<p>In the unlikely event that it ever becomes necessary to handle more than 32 axes, it would be a simple matter to modify the <em>stat[]</em> bit mask so that bit 32 applies to all axes beyond 31. However, it was not considered worth introducing the various tests required just for the sake of pandering to unrealistic possibilities.</p>
<p>In addition, <a class="el" href="wcs_8h.html#a864c99fef9f3eee29085ce42d0ee0d64" title="Subimage extraction routine for the wcsprm struct.">wcssub()</a> has a hard-coded limit of 32 coordinate elements (matching the <em>stat[]</em> bit mask), and likewise for tabs2p() (via a static helper function, tabvox()). While it would be a simple matter to generalise this by allocating memory from the heap, since tabvox() calls itself recursively and needs to be as fast as possible, again it was not considered worth pandering to unrealistic possibilities. </p>
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