+
+ // Actually, if _either_ image has blank alpha, our output will have
+ // blank alpha, too (this only tells the framework that having _both_
+ // images with blank alpha would result in blank alpha).
+ // However, understanding that would require changes
+ // to EffectChain, so postpone that optimization for later.
+ virtual AlphaHandling alpha_handling() const { return INPUT_PREMULTIPLIED_ALPHA_KEEP_BLANK; }