<!-- manual page source format generated by PolyglotMan v3.2, --> <!-- available at http://polyglotman.sourceforge.net/ --> <html> <head> <title>IM_FASTCOR(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_fastcor, im_spcor - correlate two images <h2><a name='sect1' href='#toc1'>Synopsis</a></h2> <b>#include <vips/vips.h></b> <p> <b>int im_fastcor(in, ref, out)</b> <br> <b>IMAGE *in, *ref, *out;</b> <p> <b>int im_spcor(in, ref, out)</b> <br> <b>IMAGE *in, *ref, *out;</b> <h2><a name='sect2' href='#toc2'>Description</a></h2> These functions calculate spatial correlation between two one-band images held by the image descriptors <b>in </b> and <b>ref.</b> The sizes of <b>ref </b> should be smaller than the sizes of <b>in.</b> The correlation is carried out by overlapping <b>ref </b> on the top left corner of <b>in </b> and moving it over <b>in.</b> <p> The output image is the same size as the input. The edge pixels are calculated by expanding the input image using <a href='im_embed.3.html'><b>im_embed(3)</b></a> in mode 1 (replicating edge pixels) just enough so that the output can match the input. <p> <a href='im_spcor.3.html'><b>im_spcor(3)</a> </b> calculates the spatial correlation between <b>in</b> and <b>ref</b> using the correlation coefficient from Niblack "An Introduction to Digital Image Processing,", Prentice/Hall, pp 138. The resultant coefficients are written as float numbers in <b>out. </b> The images must be char, short or ushort. <p> <a href='im_fastcor.3.html'><b>im_fastcor(3)</a> </b> simply returns the sum of squares of differences between <b>in</b> and <b>ref. </b> This is much faster, but less useful. The resultant coefficients are written as unsigned int numbers in out which has a size of in. <p> <h2><a name='sect3' href='#toc3'>Bugs</a></h2> The functions do not check for integer overflow. <h2><a name='sect4' href='#toc4'>Return Value</a></h2> The function returns 0 on success and -1 on error. <h2><a name='sect5' href='#toc5'>See Also</a></h2> <a href='im_conv.3.html'>im_conv(3)</a> , <a href='im_lrmosaic.3.html'>im_lrmosaic(3)</a> . <h2><a name='sect6' href='#toc6'>Copyright</a></h2> The National Gallery and Birkbeck College, 1990-1997. <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'>Bugs</a></li> <li><a name='toc4' href='#sect4'>Return Value</a></li> <li><a name='toc5' href='#sect5'>See Also</a></li> <li><a name='toc6' href='#sect6'>Copyright</a></li> </ul> </body> </html>
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