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NAME

       im_quantim, im_quantlut, im_spatres - quantise an image or a lut

SYNOPSIS

       #include <vips/vips.h>

       int im_quantim(in, out, no_of_bits)
       IMAGE *in, *out;
       int no_of_bits;

       int im_quantlut(lut, no_of_bits)
       IMAGE *lut;
       int no_of_bits;

       int im_spatres(in, out, step)
       IMAGE *in, *out;
       int step;

DESCRIPTION

       im_quantim()  quantises  the image file held by in using no_of_bits and
       writes the result to out.  The no_of_bits should be  between  1  and  7
       inclusive.   Input  can have any number of bands.  The function expects
       as input a valid unsigned char image.

       These functions are here for compatibility only.  You  should  use  the
       boolean   operations   im_andconst(3),   im_orconst(3),   im_shrink(3),
       im_zoom(3) and im_lowpass(3).

       im_quantlut() creates an one band unsigned char lookup table  which  is
       used  by  im_quantim(3).   The  no_of_bits  should  be  between 1 and 7
       inclusive.

       im_spatres()  reduces  the  spatial  resolution  of  in  by   averaging
       step*step  pixels  and replicating the result in out.  The function can
       be used in order to show the effect of reducing the spatial  resolution
       of   a   given  image  and  the  importance  of  post-filtering  before
       displaying.  Input can have any number of bands.

RETURN VALUE

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

SEE ALSO

       im_andconst(3), im_orconst(3), im_shrink(3), im_zoom(3)  im_lowpass(3).

COPYRIGHT

       N. Dessipris

AUTHOR

       N. Dessipris - 10/05/1991

                                  10 May 1991                    IM_QUANTIM(3)