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I think I see what you mean, but those aren't really the kind of gradients that need debanding. The most obvious bands occur when the total difference is 1 over a distance of 10 or more pixels, which would make the average difference less than 0.1.
Besides in the example you gave, 10 pixels spanning a total of 13 values, there might be a difference greater than 1 between several (at least 3) of those pixels but the difference between their rounded values and their actual value is at most 1 (or 0.5 if they were always rounded to the nearest value). True you can allow a debanding filter to change the value of a pixel by more than 1, but in my opinion that means you've started to remove noise and not just banding.
FWIW the current versions of my debanding script use statistical properties to try to distinguish between rounding errors and detail, which essentially make it impossible to simply allow it to remove slightly more 'noise'. This is a limitation that is caused by designing an algorithm specifically to remove rounding errors. If you used a general denoiser at a very low strength you should be able to simply dial up the strength to remove more noise, but those algorithm have the disadvantage that they're not as good at distinguishing between rounding errors and detail, so you might need to remove more detail in order to remove all banding.
What I'm trying to say is that both type of algorithms have their uses, but they do different things. Trying to use a debander to remove noise or a denoiser to remove banding might work but the result will be far from perfect.
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28th July 2015, 12:33
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