In Tiger, the icon preview for PNG files retained transparency if any was present. In Leopard, all my PNG files show white where there should be transparency, regardless of whether I set Photoshop to save previews or not. I'm wondering if it's just my machine.
Can you save this image to your desktop and tell me if you see a white background around the question mark? Obviously if your wallpaper is white, the test won't work.
Can you save this image to your desktop and tell me if you see a white background around the question mark? Obviously if your wallpaper is white, the test won't work.