void PixMap::copy(const PixMap& pix) {
if (size() != pix.size()) {
throw Exception("Mismatch in PixMap sizes");
}
for (int i = 0; i < size().height; ++i) {
memcpy(mutable_row(i), pix.row(i), size().width * sizeof(RgbColor));
}
}
void PixMap::composite(const PixMap& pix) {
if (size() != pix.size()) {
throw Exception("Mismatch in PixMap sizes");
}
for (int y = 0; y < size().height; ++y) {
for (int x = 0; x < size().width; ++x) {
const RgbColor& over = pix.get(x, y);
const double oa = over.alpha / 255.0;
const RgbColor& under = get(x, y);
const double ua = under.alpha / 255.0;
// TODO(sfiera): if we're going to do anything like this in the long run, we should
// require that alpha be pre-multiplied with the color components. We should probably
// also use integral arithmetic.
double red = (over.red * oa) + ((under.red * ua) * (1.0 - oa));
double green = (over.green * oa) + ((under.green * ua) * (1.0 - oa));
double blue = (over.blue * oa) + ((under.blue * ua) * (1.0 - oa));
double alpha = oa + (ua * (1.0 - oa));
set(x, y, RgbColor(alpha * 255, red / alpha, green / alpha, blue / alpha));
}
}
}
void copy_world(PixMap& to, PixMap& from, Rect bounds) {
bounds.clip_to(to.size().as_rect());
to.view(bounds).copy(from.view(bounds));
}