58 lines
1.6 KiB
Groff
58 lines
1.6 KiB
Groff
.TH IM_HEQ 3 "10 May 1991"
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.SH NAME
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im_heq, im_lhisteq, im_lhisteq_raw, im_hsp \- process an image using grey level transformations
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.SH SYNOPSIS
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#include <vips/vips.h>
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int im_heq( in, out, bandno )
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.br
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IMAGE *in, *out;
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.br
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int bandno;
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int im_lhisteq( in, out, xw, yw )
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.br
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IMAGE *in, *out;
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.br
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int xw, yw;
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int im_hsp( in, ref, out )
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.br
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IMAGE *in, *ref, *out;
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.SH DESCRIPTION
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.B im_heq(3)
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histogram equalises the unsigned char image held by the IMAGE descriptor
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in. The result is written to the IMAGE descriptor out.
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If bandno is -1 then all input bands are equalised independently. In all
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other cases the input image is equalised using the histogram of bandno only.
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The latter processing produces better results.
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.B im_hsp(3)
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maps in to out with histogram specified by the ref. All images should be
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unsigned char. Each band of the output image is specified according to the
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distribution of grey levels of the reference image according to
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im_histspec(3).
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.B im_lhisteq(3)
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histogram equalises the one channel unsigned char image pointed to by the
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Image descriptor in. The result is written to the IMAGE descriptor out.
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The histogram equalisation is based on a window of size xw by yw centered at
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the current location of each input pixel.
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In the manner of
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.B im_conv(3)
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the input image is expanded so that the output image is the same size as the
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input.
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.B im_lhisteq_raw(3)
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is as above, but does not expand the input.
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.SH RETURN VALUE
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All functions returns 0 on success and -1 on error.
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.SH SEE ALSO
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im_histgr(3), im_histplot(3), im_histspec(3), im_lineprof(3),
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im_stdif(3).
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.SH COPYRIGHT
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1991--1996 The National Gallery and Birkbeck College
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