OpenCV and Unsharp Masking Like Adobe Photoshop

Question

I am trying to implement unsharp masking like it\'s done in Adobe Photoshop. I gathered a lot of information on the interent but I\'m not sure if I\'m missing something. Here\'s

Answer 1

I'm trying to replicate Photoshop's Unsharp Mask as well. Let's ignore the Threshold for a second.

I will show you how to replicate Photoshop's Unsharp Mask using its Gaussian Blur.

Assuming O is the original image layer.

Create a new layer GB which is a Gaussian Blur applied on O.
Create a new layer which is O - GB (Using Apply Image).
Create a new layer by inverting GB - invGB.
Create a new layer which is O + invGB using Image Apply.
Create a new layer which is inversion of the previous layer, namely inv(O + invGB).
Create a new layer which is O + (O - GB) - inv(O + invGB).

When you do that in Photoshop you'll get a perfect reproduction of the Unsharp Mask.

If you do the math recalling that inv(L) = 1 - L you will get that the Unsharp Mask is USM(O) = 3O - 2B.

Yet when I do that directly in MATLAB I don't get Photoshop's results.

Hopefully someone will know the exact math.

Update

OK,
I figured it out.
In Photoshop USM(O) = O + (2 * (Amount / 100) * (O - GB))
Where GB is a Gaussian Blurred version of O.

Yet, in order to replicate Photoshop's results you must do the steps above and clip the result of each step into [0, 1] as done in Photoshop.