public static void Apply(Texture2D canvas, Rect canvasRect,
Texture2D brush, Rect brushRect,
Blend.BlendFunction blend)
{
Color[] canvasColors = canvas.GetPixelRect(canvasRect);
Color[] brushColors = brush.GetPixelRect(brushRect);
Assert.IsTrue(canvasColors.Length == brushColors.Length, "Mismatched texture rects!");
for (int i = 0; i < canvasColors.Length; ++i)
{
canvasColors[i] = blend(canvasColors[i], brushColors[i]);
}
canvas.SetPixelRect(canvasRect, canvasColors);
}