I haven’t seen many people explore the ColorMatrixFilter class, probably because it appears daunting. I’m happy to report that I comprehend the mysteries of ColorMatrixFilter now, and I thought I’d share a technique we used in our new game, Space Kitty.
Before we jump into ColorMatrixFilter, let’s ponder a different, and more commonly-used, class first: ColorTransform . Using a ColorTransform, you can “tint” any DisplayObject with color. But there’s something sneaky you can do, as well — Notice that ColorTransform gives you two parameters for each of the four color channels: Red, Green, Blue, and Alpha. One parameter is the “multiplier,” which takes the input value and (predictably) multiplies this value by a constant. The other is the “offset,” which works like addition: adding (or subtracting) another constant from the value. These two functions are applied to all four color channels of each individual pixel. That’s how the magic works.