That is one reason why I said that picture was over sharpened.Ĭode: # LimitedSharpen() ( a modded version, ) * if you look at your "sharp" image in your first post you'll see halos at the boundary between the guy's dark shirt and the lighter background. They attempt to sharpen edges without increasing noise and without producing halos. This is why filters like LSFMod (a variation of the LimitedSharpenFaster() filter) exist. Sharpening can also create halos (darker and lighter bands) around already sharp edges*. Simple sharpening also increases grain noise (conversely, the opposite, Blur(), reduces grain noise). Increasing the deblocking strength would have further reduced blocking artifacts but also blurred the overall image more. The same image, deblocked before sharpening: If you can't get that image you can try using deblocking filters before sharpening. Optimally, you want to get the image before those block artifacts have been introduced. After sharpening the edges and the corners of the blocks are accentuated. For example (4x point resize):Īs you can see, before sharpening there are 8x8 block artifacts in the source image (from compression).
If you use Sharpen() on a compressed image with a lot of blocking artifacts the edges, and especially corners, of the blocks will be accentuated.
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