imagecolortransparent giving two different values for same image
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Using the exact same image, `imagecolortransparent` is returning a different value on my local machine than it is on my server.

    $index = imagecolortransparent($image);
    // index = -1 on local machine
    // index = 16711935 on server

Both have PHP Version 5.3.5, GD 2.0.  Any ideas to why this is happening?