Add a new alpha handling method, INPUT_PREMULTIPLIED_ALPHA_KEEP_BLANK.

[movit] / overlay_effect.h

diff --git a/overlay_effect.h b/overlay_effect.h
index d26d9175110ca636890e5c03084a98a7e747560f..4c6d37a4fea6d9a95715031426eb7332fcf73346 100644 (file)
--- a/overlay_effect.h
+++ b/overlay_effect.h
@@ -21,10 +21,12 @@ public:
        virtual bool needs_srgb_primaries() const { return false; }
        virtual unsigned num_inputs() const { return 2; }
 
-       // Actually, if either image has blank alpha, our output will have
-       // blank alpha, too. However, understanding that would require changes
+       // 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_AND_OUTPUT_PREMULTIPLIED_ALPHA; }
+       virtual AlphaHandling alpha_handling() const { return INPUT_PREMULTIPLIED_ALPHA_KEEP_BLANK; }
 };
 
 #endif // !defined(_OVERLAY_EFFECT_H)