NAME
im_ifthenelse - use an unsigned char image to join two images together
SYNOPSIS
#include <vips/vips.h>
int im_ifthenelse(c, a, b, out)
IMAGE *c, *a, *b, *out;
int im_blend(c, a, b, out)
IMAGE *c, *a, *b, *out;
DESCRIPTION
im_ifthenelse builds an output image which uses some pels from a and
some from b: if the conditional image c is non-zero at that point, the
pel comes from a; if it is zero, the pel comes from b.
The conditional image c can have either 1 band, in which case entire
pels come either from a or b, or n bands, where n is the number of
bands in both a and b, in which case individual band elements are
chosen from a and b.
Images a and b must match in size, type and number of bands.
im_blend(3) works just as im_ifthenelse(3), except that instead of
selecting between a and b, values in the condition image are used to
softly blend between the two. 255 means a only, 0 means b only, 128
means 50:50.
RETURN VALUE
0 on success and -1 on error.
SEE ALSO
im_equal(3), im_and(3).
COPYRIGHT
National Gallery
AUTHOR
J. Cupitt
30 October 1992