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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
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