im_contrast_surface, im_contrast_surface_raw - Generate contrast
int im_contrast_surface( IMAGE *in, IMAGE *out, int half_win_size, int spacing );
int im_contrast_surface_raw( IMAGE *in, IMAGE *out, int half_win_size, int spacing );
These functions generate an image where the value of each pixel
represents the contrast within a square window of size 2 *
half_win_size + 1 centred on the corresponsing point in the input
The output is sub-sampled by a factor of spacing.
Input must be single-band uncoded uchar, WIO or PIO.
Output is single-band uncoded uint, WIO or PIO.
In im_contrast_surface(3), pixels beyond the edges of the input image
are considered to be have the value of the nearest pixel which is in
Alternatively, in im_contrast_surface_raw(3), pixels within
half_win_size of the edge are not calculated, and output is smaller
The functions returns 0 on success and -1 on error.
Copyright 2006, The Nottingham Trent University.
01 May 2006