for (int y = 0; y < size.height; ++y) {
uint8_t* p = grey->data()[0] + y * grey->stride()[0];
for (int x = 0; x < size.width; ++x) {
for (int y = 0; y < size.height; ++y) {
uint8_t* p = grey->data()[0] + y * grey->stride()[0];
for (int x = 0; x < size.width; ++x) {