<!-- manual page source format generated by PolyglotMan v3.2, --> <!-- available at http://polyglotman.sourceforge.net/ --> <html> <head> <title>IM_INVERTLUT(3) manual page</title> </head> <body bgcolor='white'> <a href='#toc'>Table of Contents</a><p> <h2><a name='sect0' href='#toc0'>Name</a></h2> im_invertlut - turn a set of greyscale measurements into a gamma-correcting LUT <h2><a name='sect1' href='#toc1'>Synopsis</a></h2> #include <vips/vips.h> <p> int <br> im_invertlut( DOUBLEMASK *input, IMAGE *output, int lut_size ) <p> <h2><a name='sect2' href='#toc2'>Description</a></h2> Given a mask of target values and real values, generate a LUT which will map reals to targets. Handy for linearising images from measurements of a colour chart. All values in [0,1]. Extrapolate head and tail to 0 and 1. <p> Eg. input like: <p> 4 3<br> 0.1 0.2 0.3 0.1<br> 0.2 0.4 0.4 0.2<br> 0.7 0.5 0.6 0.3<br> <p> means a patch with 10% reflectance produces an image with 20% in channel 1, 30% in channel 2, and 10% in channel 3. A patch with 20% reflectance makes an image with 40% red, 40% green and 20% blue, and so on. <p> Inputs don’t need to be sorted (we do that). Generate any precision LUT ... typically ask for 256 elements. <p> It won’t work too well for non-monotonic camera responses (should fix this). <p> Interpolation is simple piecewise linear; ought to do something better really. <p> <h2><a name='sect3' href='#toc3'>Return Value</a></h2> -1 on error, otherwise 0 <h2><a name='sect4' href='#toc4'>See Also</a></h2> <a href='im_histgr.3.html'>im_histgr(3)</a> , <a href='im_hsp.3.html'>im_hsp(3)</a> , <a href='im_heq.3.html'>im_heq(3)</a> , <a href='im_identity.3.html'>im_identity(3)</a> . <h2><a name='sect5' href='#toc5'>Copyright</a></h2> 2001, National Gallery <p> <hr><p> <a name='toc'><b>Table of Contents</b></a><p> <ul> <li><a name='toc0' href='#sect0'>Name</a></li> <li><a name='toc1' href='#sect1'>Synopsis</a></li> <li><a name='toc2' href='#sect2'>Description</a></li> <li><a name='toc3' href='#sect3'>Return Value</a></li> <li><a name='toc4' href='#sect4'>See Also</a></li> <li><a name='toc5' href='#sect5'>Copyright</a></li> </ul> </body> </html>
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