| .TH IM_HEQ 3 "10 May 1991" |
| .SH NAME |
| im_heq, im_lhisteq, im_lhisteq_raw, im_hsp \- process an image using grey level transformations |
| .SH SYNOPSIS |
| #include <vips/vips.h> |
| |
| int im_heq( in, out, bandno ) |
| .br |
| IMAGE *in, *out; |
| .br |
| int bandno; |
| |
| int im_lhisteq( in, out, xw, yw ) |
| .br |
| IMAGE *in, *out; |
| .br |
| int xw, yw; |
| |
| int im_hsp( in, ref, out ) |
| .br |
| IMAGE *in, *ref, *out; |
| |
| .SH DESCRIPTION |
| .B 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. |
| |
| .B 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 specified according to the |
| distribution of grey levels of the reference image according to |
| im_histspec(3). |
| |
| .B 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 |
| .B im_conv(3) |
| the input image is expanded so that the output image is the same size as the |
| input. |
| |
| .B im_lhisteq_raw(3) |
| is as above, but does not expand the input. |
| |
| .SH RETURN VALUE |
| All functions returns 0 on success and -1 on error. |
| .SH SEE ALSO |
| im_histgr(3), im_histplot(3), im_histspec(3), im_lineprof(3), |
| im_stdif(3). |
| .SH COPYRIGHT |
| 1991--1996 The National Gallery and Birkbeck College |
