Faster Bilateral Sharpening

[jsachs]

Yes, each of the other places bilateral was used you can now select guided.

There are some interesting possible applications for guided filtering other than blurring (which is a simpler case where the input and guide image are the same) but I have not thought that far ahead.

[tomczak]

In Brightness Curve/Advanced there are now two options for low pass but the default still seems to be BS. When I change BS to Guided in Settings and hit OK, on reopening the transformation BS returns.

[tomczak]

In Multipass Sharpen, when I change the methods and hit the running man, the Mean Image is displayed as being calculated in both, and it appears that there is no speed advantage for Guided. Is it possible that the transformation still uses BS algorithm in both cases?

[tomczak]

I tried Multipass sharpening on the Sharpen Test Pattern. If the BS mode is chosen, Sharpen Threshold seems to work as expected - it blurs within the edges. In Guided mode, it still blurs, but I can't see the edge preservation no matter what Sharpen Threshold value is.

[tomczak]

I just wanted to add how I typically adjust or diagnose BS (and now Guided).

By default, I leave Blur Threshold at 100%, Sharpen Factor at 0%, and Sharpen Threshold at 100%. This let me adjust Blur Radius by seeing which areas will be blurred and by how much (to be later sharpened by increasing the Sharpen Factor, but not yet).

Then I adjust Blur Threshold to exclude the larger, more contrasty edges from blurring (and thus sharpening and potential halos).

Dialing down the Sharpen Threshold then is to my mind similar to not blurring the low roughness areas like noise and grain (kind of similar functionally to the low roughness threshold slider in AS, but without control of the softness of the transition).

Once I'm happy with what's blurred what's not, I adjust Sharpen Factor and Halo Limits to actually sharpen the blurred areas of the image.

Maybe this technique and the fact that Guided operates differently (and the sliders may not mean the same thing as in BS) are the reasons that I don't seem to see what I expect in Guided mode?

[jsachs]

I fixed the problem with Brightness Curve for the next release.

There is a speed increase for Guided only for large radius settings. For small settings it may be slower.

>> I tried Multipass sharpening on the Sharpen Test Pattern. If the BS mode is chosen, Sharpen Threshold seems to work as expected - it blurs within the edges. In Guided mode, it still blurs, but I can't see the edge preservation no matter what Sharpen Threshold value is.

I'm not sure what you expect to see but it looks to me like two methods are very similar. Edge preservation changes with the Blur Threshold, not the Sharpen Threshold.