Thanks very much for your suggestions. It's nice to know there is a solution for those who have the editing software, skills and patience to fix the problem. I'm not sure it sounds like a very good use of my time though. I'll try the GIF technique and if that doesn't take too long (there are probably 100 of them if you count picture and disabled picture) that may be worth a try. Otherwise, I may have to live with a bit of an aura around the images.