added comment about image alpha

diff --git a/lib/gfxdevice.h b/lib/gfxdevice.h
index b4dd19f..f852814 100644 (file)
--- a/lib/gfxdevice.h
+++ b/lib/gfxdevice.h
@@ -55,6 +55,8 @@ typedef struct _gfxmatrix
 
 typedef struct _gfximage
 {
 
 typedef struct _gfximage
 {

+    /* if the data contains an alpha layer (a != 255), the
+       r,g,b values will have to be premultiplied */

     gfxcolor_t*data;
     int width;
     int height;
     gfxcolor_t*data;
     int width;
     int height;