Probably a significantly long time. That said, I do wonder if you need to actually run this at the resolution of the output image. Since really this is just cha

Probably a significantly long time. That said, I do wonder if you need to actually run this at the resolution of the output image. Since really this is just changing the tones in the image and not altering the details, you could probably optimize the algorithm heavily such that it works for high resolution images quickly. As an example, I used frequency separation to split the detail layer from the tone layer in the original, high resolution stock photo of SF. From there I took the lower res (25% size) output from this script and used it as my tone layer. The results are OK: http://i.imgur.com/oakLUiE.jpg http://i.imgur.com/oakLUiE.jpg It has the same overall tones, and some of the sharpness is preserved at a high resolution. My 30 second approach suffers from some edge glow, but I'm sure it could be greatly improved in an efficient, automated way.