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You probably want to set sigma to be a fraction of the radius, rather than a fixed value. Sigma controls the actual shape of the filter, while radius just controls how far out the filter gets cut off (as Gaussians truly have infinite radius, so we have to cut them off somewhere to use them in practice). With sigma set to 0.5, you're making a filter that's ...


2

Each color is conceptually treated independently. If they were concatenated, multiplying a value with a color close to the maximum possible value for one channel could cause it to overflow into the lower bits of the next. That said, if you’re asking for performance purposes, a lot of the hardware that does this kind of work can perform all of the per-channel ...


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