X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=mix_effect.h;h=4ef62fe9a2454c4754635fd62566e93bbb63a96b;hp=8032062077491e7b545fc0df5e208d0b13f20a45;hb=37f56fcbe571b2322243f6de59494bf9e0cbb37a;hpb=f99ad333a7acbb6c8c995dbb036484ae8940c490

diff --git a/mix_effect.h b/mix_effect.h
index 8032062..4ef62fe 100644
--- a/mix_effect.h
+++ b/mix_effect.h
@@ -1,7 +1,10 @@
 #ifndef _MIX_EFFECT_H
 #define _MIX_EFFECT_H 1
 
-// Combine two images: a*x + b*y. (If you set a within [0,1] and b=1-a, you will get a fade.)
+// Combine two images: a*x + b*y. If you set a within [0,1] and b=1-a,
+// you will get a fade; if not, you may get surprising results (consider alpha).
+
+#include <string>
 
 #include "effect.h"
 
@@ -14,6 +17,10 @@ public:
 	virtual bool needs_srgb_primaries() const { return false; }
 	virtual unsigned num_inputs() const { return 2; }
 
+	// TODO: In the common case where a+b=1, it would be useful to be able to set
+	// alpha_handling() to INPUT_PREMULTIPLIED_ALPHA_KEEP_BLANK. However, right now
+	// we have no way of knowing that at instantiation time.
+
 private:
 	float strength_first, strength_second;
 };