I'm trying to determine what "filter" has been applied to an image. I have the original, raw image and the processed image. The processed image has been put through a pipeline (black box) that does various things to the image in an iterative manner.
The filter, as far as I can tell, is similar to an unsharp-mask, but with "negative bowls" mitigated. However, the processed image cannot be reproduced by a simple unsharp mask.
I've attempted to measure the "filter function" by taking the ratio of the power spectra of the raw and unprocessed images, but the best I've been able to do with that is unsharp mask with a non-gaussian smoothing function.
What methods are available for determining the filter applied to an image?
(not related to Determining the type of filter on an image)