Why does Quicktime not display png files properly?

    Aug 25 2008 | 8:11 pm
    Hi all I am loading png files with an alpha channel and they do not display properly in Quicktime. I have attached three images to show the difference - The Original Image, The image displayed in Quicktime and a difference image of the two. In the difference image you can see the alpha is jagged and there is a slight gradient to the right.
    I don't have to use PNG files but they are so far the best of tiff,jpg and tga.
    Any suggestions as to why this is happeing or an alternative codec would be great