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<a href='#toc'>Table of Contents</a><p>
<h2><a name='sect0' href='#toc0'>Name</a></h2>
im_log_dmask, im_log_imask - create a laplacian of gaussian (log) DOUBLEMASK
or INTMASK
<h2><a name='sect1' href='#toc1'>Synopsis</a></h2>
<b></b> #include <vips/vips.h>
<p>
<p> <b>DOUBLEMASK *im_log_dmask( name,
sigma, min_amplitude )</b> <br>
char *name; <br>
double sigma, min_amplitude;
<p> <b>INTMASK *im_log_imask( name, sigma, min_amplitude
)</b> <br>
char *name; <br>
double sigma, min_amplitude;
<h2><a name='sect2' href='#toc2'>Description</a></h2>
Both functions create a circularly
symmetric laplacian of Gaussian mask. The size of the mask is determined
by the variable min_amplitude; if for instance the value .1 is entered this
means that the produced mask is clipped at values within 10 persent of
zero, and where the change between mask elements is less than 10%. The mask
can be directly used with the vasari convolution programs, the default
offset set is 0.
<p> The program uses the following equation: (from Handbook
of Pattern Recognition and image processing by Young and Fu, AP 1986 pages
220-221):
<p> H(r) = (1 / (2 * M_PI * s4)) *<br>
(2 - (r2 / s2)) * <br>
<tt> </tt> <tt> </tt> exp(-r2 / (2 * s2))<br>
<p> where s2 = sigma * sigma, s4=s2 * s2, r2 = r * r. The generated mask
has odd size and its maximum value is normalised to either 100 (log_imask)
or to 1.0 (log_dmask)
<p> <b>im_log_dmask()</b> creates a DOUBLEMASK laplacian of
Gaussian mask with maximum value normalised to 1.0.
<p> <b>im_log_imask()</b> creates
a INTMASK laplacian of Gaussian mask with maximum value normalised to 100.
<h2><a name='sect3' href='#toc3'>Returned Value:</a></h2>
The functions return NULL on erorr.
<h2><a name='sect4' href='#toc4'>See Also</a></h2>
<a href='im_gauss_dmask.3.html'>im_gauss_dmask(3)</a>
,
<a href='im_conv.3.html'>im_conv(3)</a>
<h2><a name='sect5' href='#toc5'>Copyright</a></h2>
<br>
N. Dessipris
<h2><a name='sect6' href='#toc6'>Author</a></h2>
N. Dessipris - 06/12/1991 <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'>Returned Value:</a></li>
<li><a name='toc4' href='#sect4'>See Also</a></li>
<li><a name='toc5' href='#sect5'>Copyright</a></li>
<li><a name='toc6' href='#sect6'>Author</a></li>
</ul>
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