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=head1 NAME
map.c - inplace image mapping and related functionality
i_map(srcimage, coeffs, outchans, inchans)
Converts images from one format to another, typically in this case for
converting from RGBA to greyscale and back.
#include "imager.h"
=item i_map(im, mapcount, maps, chmasks)
maps im inplace into another image.
Each map is a unsigned char array of 256 entries, its corresponding
channel mask is the same numbered entry in the chmasks array.
If two maps apply to the same channel then the second one is used.
If no map applies to a channel then that channel is not altered.
mapcount is the number of maps.
i_map(i_img *im, unsigned char (*maps)[256], unsigned int mask) {
i_color *vals;
int x, y;
int i, ch;
int minset = -1, maxset = 0;
mm_log((1,"i_map(im %p, maps %p, chmask %u)\n", im, maps, mask));
if (!mask) return; /* nothing to do here */
for(i=0; i<im->channels; i++)
if (mask & (1<<i)) {
if (minset == -1) minset = i;
maxset = i;
mm_log((1, "minset=%d maxset=%d\n", minset, maxset));
vals = mymalloc(sizeof(i_color) * im->xsize);
for (y = 0; y < im->ysize; ++y) {
i_glin(im, 0, im->xsize, y, vals);
for (x = 0; x < im->xsize; ++x) {
for(ch = minset; ch<=maxset; ch++) {
if (!maps[ch]) continue;
vals[x].channel[ch] = maps[ch][vals[x].channel[ch]];
i_plin(im, 0, im->xsize, y, vals);
=head1 SEE ALSO
=head1 AUTHOR
Arnar M. Hrafnkelsson <>
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