r = Sqrt[(x - .5)^2 + (y - .5)^2] a = ArcTan[x - .5, y - .5] rn = r^2.5/.5
/* NB: arctan is not really necessary since Cos[a] = (x - .5)/r and Sin[a] = (y - .5)/r */
And then remap your pixels according to:
x -> rnCos[a] + .5 y -> rnSin[a] + .5
r = Sqrt[(x - .5)^2 + (y - .5)^2] a = ArcTan[x - .5, y - .5] rn = r^2.5/.5
/* NB: arctan is not really necessary since Cos[a] = (x - .5)/r and Sin[a] = (y - .5)/r */
And then remap your pixels according to:
x -> rnCos[a] + .5 y -> rnSin[a] + .5