1IM_HEQ(3)                  Library Functions Manual                  IM_HEQ(3)
2
3
4

NAME

6       im_heq,  im_lhisteq,  im_lhisteq_raw,  im_hsp  - process an image using
7       grey level transformations
8

SYNOPSIS

10       #include <vips/vips.h>
11
12       int im_heq(in, out, bandno)
13       IMAGE *in, *out;
14       int bandno;
15
16       int im_lhisteq(in, out, xw, yw)
17       IMAGE *in, *out;
18       int xw, yw;
19
20       int im_hsp(in, ref, out)
21       IMAGE *in, *ref, *out;
22
23

DESCRIPTION

25       im_heq() histogram equalises the unsigned char image held by the  IMAGE
26       descriptor  in.  The result is written to the IMAGE descriptor out.  If
27       bandno is 0 then all input bands are equalised independently.   In  all
28       other  cases the input image is equalised using the histogram of bandno
29       only.  The latter processing produces better results.
30
31       im_hsp() maps in to out with  histogram  specified  by  the  ref.   All
32       images should be unsigned char.  Each band of the output image is spec‐
33       ified according to the distribution of grey  levels  of  the  reference
34       image according to im_histspec(3).
35
36       im_lhisteq()  histogram  equalises  the one channel unsigned char image
37       pointed to by the Image descriptor in.  The result is  written  to  the
38       IMAGE  descriptor out.  The histogram equalisation is based on a window
39       of size xw by yw centered at the current location of each input  pixel.
40       The  produced  image  has  a black border of sizes xw/2 (left), xw-xw/2
41       (right), yw/2 (top) and yw-yw/2 (bottom).
42
43       im_lhisteq_raw() is as above, but does not add the black border to  the
44       output image.
45
46

RETURN VALUE

48       All functions returns 0 on success and -1 on error.
49

SEE ALSO

51       im_histgr(3),     im_histplot(3),    im_histspec(3),    im_lineprof(3),
52       im_stdif(3).
53

55       1991--1996 The National Gallery and Birkbeck College
56
57
58
59                                  10 May 1991                        IM_HEQ(3)
Impressum