I can confirm this--it’s happening to me too.
Transparent images are being modified by Magento somehow (using GD?) and being done incorrectly. All GIFs with transparency have their transparency replaced with black.
This is definitely happening on the server-side, not due to user error. It is not being done by CSS, because I can open the image by itself in a browser window, and it is not the same as the image I imported--it even has a different name. It appears that *perhaps* Magento is resizing images to (e.g.) 135 x 135 (even though I already had them at that size), and doing it poorly. (@Varien:) It would be very nice to be able to control this, rather than having it mangle my already perfectly sized and optimized images.
Here’s the URL format of the bad images:
Here’s the URL format of good images, exactly as I created them:
(@Varien:) If the problem is created by something underneath Magento (like GD) then it would be helpful if Magento would verify that the version of GD is correct, etc., during installation, and give a warning that such things as this will happen, as well as allow the (admin)user to turn off this server-side image processing, and allow them to specify whether to use the image *as*uploaded* or the processed image.