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nagadomi / waifu2x

Image Super-Resolution for Anime-Style Art
http://waifu2x.udp.jp/
MIT License
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Noise reduction produces more color banding #364

Open CarbonPool opened 3 years ago

CarbonPool commented 3 years ago

I captured some pixels.

The original image: p

UpPhoto DeNoise 3: p(UpPhoto)(noise)(Level3)

nagadomi commented 3 years ago

To my eyesight, that appears to be a smaller difference than the dirt on the monitor. Also, noise level 3 is the model with the worst preservation of the original image.

CarbonPool commented 3 years ago

p2

I further sharpened this original image under the cnet denoise level3 model. Compared with level2, the results are surprising. Could it be a problem with the program model? But I prefer level3, which can eliminate the jaggedness of some animated illustration lines.

CarbonPool commented 3 years ago

I tried to use the fastNlMeansDenoisingColored function in opencv to reduce noise, using a stronger level, the same serious color band appeared

nagadomi commented 3 years ago

A typical adaptive smoothing algorithm applies smoothing where the color gradient is low and not where the gradient is high. This preserves the color banding (steps) once it occurs.