4 rubthru_targ_noalpha(i_img *im, i_img *src,
6 int src_minx, int src_miny,
7 int src_maxx, int src_maxy) {
16 if (im->channels == 3 && src->channels == 4) {
18 chans[0] = 0; chans[1] = 1; chans[2] = 2;
21 else if (im->channels == 3 && src->channels == 2) {
23 chans[0] = chans[1] = chans[2] = 0;
26 else if (im->channels == 1 && src->channels == 2) {
32 i_push_error(0, "rubthru can only work where (dest, src) channels are (3,4), (4,4), (3,2), (4,2), (1,2) or (2,2)");
36 #code im->bits <= 8 && src->bits <= 8
38 IM_COLOR pv, orig, dest;
41 for(y = src_miny; y < src_maxy; y++) {
43 for(x = src_minx; x < src_maxx; x++) {
44 IM_GPIX(src, x, y, &pv);
45 IM_GPIX(im, ttx, tty, &orig);
46 alpha = pv.channel[alphachan];
47 for (ch = 0; ch < chancount; ++ch) {
48 dest.channel[ch] = (alpha * pv.channel[chans[ch]]
49 + (IM_SAMPLE_MAX - alpha) * orig.channel[ch])/IM_SAMPLE_MAX;
51 IM_PPIX(im, ttx, tty, &dest);
61 rubthru_targ_alpha(i_img *im, i_img *src, int tx, int ty,
62 int src_minx, int src_miny,
63 int src_maxx, int src_maxy) {
71 if (im->channels == 4 && src->channels == 4) {
73 chans[0] = 0; chans[1] = 1; chans[2] = 2;
76 else if (im->channels == 4 && src->channels == 2) {
78 chans[0] = chans[1] = chans[2] = 0;
81 else if (im->channels == 2 && src->channels == 2) {
87 i_push_error(0, "rubthru can only work where (dest, src) channels are (3,4), (4,4), (3,2), (4,2), (1,2) or (2,2)");
91 targ_alpha_chan = im->channels - 1;
93 #code im->bits <= 8 && src->bits <= 8
94 IM_WORK_T src_alpha, orig_alpha, dest_alpha, remains;
95 IM_COLOR pv, orig, dest;
98 for(y = src_miny; y < src_maxy; y++) {
100 for(x = src_minx; x < src_maxx; x++) {
101 IM_GPIX(src, x, y, &pv);
102 src_alpha = pv.channel[alphachan];
104 remains = IM_SAMPLE_MAX - src_alpha;
105 IM_GPIX(im, ttx, tty, &orig);
106 orig_alpha = orig.channel[targ_alpha_chan];
107 dest_alpha = src_alpha + (remains * orig_alpha) / IM_SAMPLE_MAX;
109 for (ch = 0; ch < chancount; ++ch) {
111 ( src_alpha * pv.channel[chans[ch]]
112 + remains * orig.channel[ch] * orig_alpha / IM_SAMPLE_MAX
116 dest.channel[targ_alpha_chan] = dest_alpha;
117 IM_PPIX(im, ttx, tty, &dest);
128 =item i_rubthru(im, src, tx, ty, src_minx, src_miny, src_maxx, src_maxy )
132 Takes the sub image I<src[src_minx, src_maxx)[src_miny, src_maxy)> and
133 overlays it at (I<tx>,I<ty>) on the image object.
135 The alpha channel of each pixel in I<src> is used to control how much
136 the existing colour in I<im> is replaced, if it is 255 then the colour
137 is completely replaced, if it is 0 then the original colour is left
144 i_rubthru(i_img *im, i_img *src, int tx, int ty, int src_minx, int src_miny,
145 int src_maxx, int src_maxy) {
146 if (im->channels == 1 || im->channels == 3)
147 return rubthru_targ_noalpha(im, src, tx, ty, src_minx, src_miny,
150 return rubthru_targ_alpha(im, src, tx, ty, src_minx, src_miny,