I’ve got a render going through a rew compositing nodes. Inside Blender, when I view the image in the image editor, the transparent/semitransparent pixels around the edges of my object have the correct color value when I sample them with the mouse. When I save the image, I believe something related to premutiplied alpha is being applied, because all pixels that had transparency turn white. I believe this is because the color values are being divided by the alpha value and then clamped to white (though their transparency is maintainted), but I have no way of really knowing. Can I prevent Blender from doing this? The image in the image editor is exactly what I need. I want the pixels surrounding the object to have the same color value as the object while their alpha values fade, so I can composite them correctly in a game.
Blend file:
https://copy.com/lyTMvMvHXUJE
The problem pixels in this case are the grey pixels on the bottom edge. I blender, it’s grey all the way to the bottom edge of the image, until I save it. Those pixels are all white in the saved image, if you open it in, for example, GIMP and remove the alpha channel.
The alpha convert node at the end of the compositing nodes is an attempt to fix this problem. It doesn’t seem to be working though.