+ /*
+ * We use alpha from the color conversion, not separate one.
+ * We had to include it for transpose, hence it will get converted
+ * too (albeit when doing transpose after conversion, that would
+ * no longer be the case necessarily).
+ * (It works only with 4 channel dsts, e.g. rgbx formats, because
+ * otherwise we really have padding, not alpha, included.)
+ */
+ has_alpha = true;