57 lines
1.6 KiB
Groff
57 lines
1.6 KiB
Groff
.TH LOG_MASKS 3 "6 December 1991"
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.SH NAME
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im_log_dmask, im_log_imask \- create a laplacian of gaussian (log)
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DOUBLEMASK or INTMASK
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.SH SYNOPSIS
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.B
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#include <vips/vips.h>
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.B DOUBLEMASK *im_log_dmask( name, sigma, min_amplitude )
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.br
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char *name;
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.br
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double sigma, min_amplitude;
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.B INTMASK *im_log_imask( name, sigma, min_amplitude )
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.br
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char *name;
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.br
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double sigma, min_amplitude;
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.SH DESCRIPTION
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Both functions create a circularly symmetric laplacian of Gaussian mask. The
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size of the mask is determined by the variable min_amplitude; if for instance
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the value .1 is entered this means that the produced mask is clipped at values
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within 10 persent of zero, and where the change between mask elements is less
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than 10%.
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The mask can be directly used with the vasari convolution
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programs, the default offset set is 0.
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The program uses the following equation: (from Handbook of Pattern Recognition
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and image processing by Young and Fu, AP 1986 pages 220-221):
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H(r) = (1 / (2 * M_PI * s4)) *
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(2 - (r2 / s2)) *
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exp(-r2 / (2 * s2))
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where s2 = sigma * sigma, s4=s2 * s2, r2 = r * r. The generated mask has odd
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size and its
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maximum value is normalised to either 100 (log_imask) or to 1.0 (log_dmask)
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.B im_log_dmask()
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creates a DOUBLEMASK laplacian of Gaussian mask with maximum value normalised
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to 1.0.
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.B im_log_imask()
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creates a INTMASK laplacian of Gaussian mask with maximum value normalised
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to 100.
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.SH RETURNED VALUE:
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The functions return NULL on erorr.
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.SH SEE ALSO
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im_gauss_dmask(3), im_conv(3)
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.SH COPYRIGHT
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.br
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N. Dessipris
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.SH AUTHOR
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N. Dessipris \- 06/12/1991
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