this is a straightforward implementation of richardson lucy deconvolution. it's inspired by rawtherapee's "capture sharpening" and can help reduce some blur caused by optical low pass filters, blurry lenses, or soft demosaicing.
it should be run on linear data just after demosaicing.
sigmathe parameter of the gaussian blur assumed to have deteriorated the imageiternumber of iterations to run the algorithm for. runtime scales pretty much linearly in this number.