68 lines
1.5 KiB
Groff
68 lines
1.5 KiB
Groff
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.TH IM_FASTCOR 3 "14 May 1991"
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.SH NAME
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im_fastcor, im_spcor \- correlate two images
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.SH SYNOPSIS
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.B #include <vips/vips.h>
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.B int im_fastcor(in, ref, out)
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.br
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.B IMAGE *in, *ref, *out;
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.B int im_spcor(in, ref, out)
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.br
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.B IMAGE *in, *ref, *out;
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.SH DESCRIPTION
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These functions calculate spatial correlation between two
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one-band images held
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by the image descriptors
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.B in
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and
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.B ref.
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The sizes of
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.B ref
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should be smaller than
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the sizes of
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.B in.
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The correlation is carried out by overlapping
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.B ref
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on the top
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left corner of
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.B in
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and moving it over
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.B in.
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The output image is the same size as the input. The edge pixels are calculated
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by expanding the input image using
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.B im_embed(3)
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in mode 1 (replicating edge pixels) just enough so that the output can match
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the input.
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.B im_spcor(3)
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calculates the spatial correlation between
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.B in
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and
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.B ref
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using the
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correlation coefficient from Niblack "An Introduction to Digital Image
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Processing,", Prentice/Hall, pp 138. The resultant coefficients are written
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as float numbers in
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.B out.
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The images must be char, short or ushort.
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.B im_fastcor(3)
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simply returns the sum of squares of differences between
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.B in
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and
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.B ref.
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This is much faster, but less useful. The resultant coefficients are written
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as unsigned int numbers in out which has a size of in.
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.SH BUGS
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The functions do not check for integer overflow.
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.SH RETURN VALUE
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The function returns 0 on success and -1 on error.
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.SH SEE ALSO
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im_conv(3), im_lrmosaic(3).
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.SH COPYRIGHT
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The National Gallery and Birkbeck College, 1990-1997.
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