im_invert - inverts an image pointed by an image descriptor.
int im_invert(in, out)
IMAGE *in, *out;
im_invert inverts the image held by image descriptor in and writes the
result on the image descriptor out. The function works on FMTUCHAR
images only. The result at point x of the input image is 255-x at the
output image. Input can have any no of channels.
This is not a generally useful program -- it is included as an
example of a very simple new-style IO function. Feel the power of the
The function returns 0 on success and -1 on error.
im_add(3), im_lintra(3), im_multiply(3).
J. Cupitt - 21/7/93
11 April 1990