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NAME

       im_freqflt - filters an image with a float filter mask in the frequency
       domain

SYNOPSIS

       #include <vips/vips.h>

       int im_freqflt(in, filtermask, out)
       IMAGE *in, *filtermask, *out;

DESCRIPTION

       im_freqflt() performs filtering in the frequency domain  of  the  input
       image  held  by  the  image  descriptor  in  with  a  mask  held by the
       descriptor filtermask and writes the result  on  the  image  descriptor
       out.

       Image  sizes  should  be  power  of  two and less or equal to 512.  All
       images should be one channel square images.  Image filtermask is a non-
       complex  one  channel  image created by im_create_fmask().  Input image
       can be any type.  If input is complex, in and filtermask are multiplied
       using the function im_cmultim(3).

       If  input  is  not  complex  then  it is transformed into the frequency
       domain and then it is multiplied with the filtermask.   In  the  latter
       case the result is inverse fourier transformed and clipped to the input
       image format using the function im_clip2fmt(3).

RETURN VALUE

       The function returns 0 on success and -1 on error.

BUGS

       The function has not been fully tested.

SEE ALSO

       im_fwfft(3), im_invfft(3), im_create_fmask(3), im_cmultim(3).

COPYRIGHT

       N. Dessipris

AUTHOR

       N. Dessipris - 10/05/1991

                                  10 May 1991                    IM_FOURFLT(3)