crop grayscale node for substance designer

When I just learned Substance Designer, I often couldn't adapt to it. For example, I could not select regional tools and modify local images.

I found that there was a hidden function in the official Corp node. I modified it and exposed the function to achieve a function similar to Photoshop.

This, combined with the FFD nodes I published earlier, allows for local distortion adjustments. It is very convenient for some hard surfaces.