im_heq(3) im_heq(3)
NAME
im_heq, im_lhisteq, im_lhisteq_raw, im_hsp - process an image using
grey level transformations
SYNOPSIS
#include <vips/vips.h>
int im_heq( in, out, bandno )
IMAGE *in, *out;
int bandno;
int im_lhisteq( in, out, xw, yw )
IMAGE *in, *out;
int xw, yw;
int im_hsp( in, ref, out )
IMAGE *in, *ref, *out;
DESCRIPTION
im_heq(3) histogram equalises the unsigned char image held by the IMAGE
descriptor in. The result is written to the IMAGE descriptor out. If
bandno is -1 then all input bands are equalised independently. In all
other cases the input image is equalised using the histogram of bandno
only. The latter processing produces better results.
im_hsp(3) maps in to out with histogram specified by the ref. All
images should be unsigned char. Each band of the output image is spec-
ified according to the distribution of grey levels of the reference
image according to im_histspec(3).
im_lhisteq(3) histogram equalises the one channel unsigned char image
pointed to by the Image descriptor in. The result is written to the
IMAGE descriptor out. The histogram equalisation is based on a window
of size xw by yw centered at the current location of each input pixel.
In the manner of im_conv(3) the input image is expanded so that the
output image is the same size as the input.
im_lhisteq_raw(3) is as above, but does not expand the input.
RETURN VALUE
All functions returns 0 on success and -1 on error.
SEE ALSO
im_histgr(3), im_histplot(3), im_histspec(3), im_lineprof(3),
im_stdif(3).
COPYRIGHT
1991--1996 The National Gallery and Birkbeck College
10 May 1991 im_heq(3)
vips 7.18.1 - Generated Sat Apr 18 09:44:30 CDT 2009