memset(data, 0, inw*inh*sizeof(pixel32));
for (y = 0; y < h; ++y) {
drx = (float)(sf->data.planar.secondary->r - sf->data.planar.primary->r);
memset(data, 0, inw*inh*sizeof(pixel32));
for (y = 0; y < h; ++y) {
drx = (float)(sf->data.planar.secondary->r - sf->data.planar.primary->r);