X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=overlay_effect.h;h=66ff31b94be55d19ffacb7714051baa2c785493c;hp=d26d9175110ca636890e5c03084a98a7e747560f;hb=ad66f9714e4a36008c341355700272a52484a785;hpb=5d4c0425579de66b3e2dd7d0095e890278f8efcf

diff --git a/overlay_effect.h b/overlay_effect.h
index d26d917..66ff31b 100644
--- a/overlay_effect.h
+++ b/overlay_effect.h
@@ -10,6 +10,8 @@
 //
 // The first input is the bottom, and the second is the top.
 
+#include <string>
+
 #include "effect.h"
 
 class OverlayEffect : public Effect {
@@ -21,10 +23,12 @@ 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)