int const this_bpp = 3;
for (int ty = start_ty, oy = start_oy; ty < size().height && oy < other->size().height; ++ty, ++oy) {
uint8_t* tp = data()[0] + ty * stride()[0] + start_tx * this_bpp;
uint8_t* op = other->data()[0] + oy * other->stride()[0];
for (int tx = start_tx, ox = start_ox; tx < size().width && ox < other->size().width; ++tx, ++ox) {
float const alpha = float (op[3]) / 255;
int const this_bpp = 3;
for (int ty = start_ty, oy = start_oy; ty < size().height && oy < other->size().height; ++ty, ++oy) {
uint8_t* tp = data()[0] + ty * stride()[0] + start_tx * this_bpp;
uint8_t* op = other->data()[0] + oy * other->stride()[0];
for (int tx = start_tx, ox = start_ox; tx < size().width && ox < other->size().width; ++tx, ++ox) {
float const alpha = float (op[3]) / 255;