app: add "hard mix" blend mode
Similar to the Photoshop mode of the same name. Assigns either 0 or 1 to each of the channels, depending on whether the sum of source and destination channel values is less than, or greater than (or equals to), one, respectively. This is equivalent to inverting the source, and using it to perform per-pixel, per-channel threshold against the destination, which is useful for various effects.
Showing with 75 additions and 11 deletions