+ if (format == GL_ALPHA) {
+ for (unsigned i = 0; i < width * height; ++i) {
+ out_data[i] = temp[i * 4 + 3];
+ }
+ } else if (format == GL_BLUE) {
+ for (unsigned i = 0; i < width * height; ++i) {
+ out_data[i] = temp[i * 4 + 2];
+ }
+ } else {
+ for (unsigned i = 0; i < width * height; ++i) {
+ out_data[i] = temp[i * 4];
+ }