# Multiply RGB values by their alpha value
	private fun premultiply_alpha(width, height: Int) `{
		uint8_t *bytes = (uint8_t *)self;
		int x, y, i = 0;
		for(y = 0; y < height; y ++) {
			for(x = 0; x < width; x ++) {
				int a = bytes[i+3];
				bytes[i  ] = bytes[i  ] * a / 255;
				bytes[i+1] = bytes[i+1] * a / 255;
				bytes[i+2] = bytes[i+2] * a / 255;
				i += 4;
			}
		}
	`}