In case you didn't under stand what i did in previous post I'll explain better.\
using
http://pixlr.com/editor/
start with circle image
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make new transparent image that has a height 2x the original.
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select original image, select filter/polar coordinates/polar to rect
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copy the result of step 3, and paste into step 2, Rotate canvas 180 degrees, using top right tool move layer to desired location, do a second paste, and again adjust position of layer (it maybe needed to switch back and forth between layers),To prevent a hole be sure to position Image to the top of the canvas. save image close image
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Open image just saved, set image size 256x256
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Go back to select filter/polar coordinates/rect to polar, save and done