Legacy ImageMagick Discussions Archive

I think there are new modules in OpenCV for that.

What about doing it using Wavelets / Image Pyramid?

You corrected your answer after I wrote that the magic happens due to clipping in each step.

Yet clipping, since it is Non Linear, must be done at each iteration and not like you wrote.

Try it by yourself.

It turns out the magic happens when after each addition / subtraction operation you clip the image into its range.

Thank You for the simulations.

Yet again, what's interesting here is why Photoshop does it and why the direct calculation is different from the "Long Calculation"?

Let's try it again. Can wee agree that inv(L) = White - L? USM(O) = O + (O - B) - inv(O + inv(B)) = 2O - B - (White - (O + (White - B))) = 2O - B - (White - (O + White - B)) = 2O - B - (White - O - White + B) = 2O - B - White + O + White - B = 3O - 2B. So I was right whether it is a [0, 1] image or ...

I think the documentation isn't updated since I clearly see that GIMP is close to Photoshop.

I promise you Photoshop does what I wrote above.

I just don't know why.

Leave the threshold aside for the aske of this dicussion. Open Photoshop and try: USM(O) = O + (O - GB) - Which is as you set Amount to 100. You'll see it is not replicates Photoshop's USM. Then try the method I suggested: USM(O) = O + (O - GB) - inv(O - inv(GB)) And you'll see it's 100%. The first ...

There's a big difference.
Photoshop does something like "Dark Halos" + "Light Halos".

See what I linked.

I think Image Magick does USM(O) = O + Amount * (O - GB)
Photoshop is different.

I think Photoshop works a bit different which produces much better results:

viewtopic.php?f=22&t=25477

I think Photoshop's Unsharp Mask is completely different from IM and GIMP.
Look here:

viewtopic.php?f=22&t=25477

Hello, Has anyone succeeded replicating Photoshop's Gaussian Blur and Unsharp Mask? When I say replicating, I mean up to a rounding error or something like that. It looks like Photoshop is doing something beyond the classic and I want to know what exactly to be able to reproduce things I do in ...