Easy to derive!
Just set your texture to 256X512.


Make sure your opacity is the same size than your texture.

This rug has no frills. Off you go! Now create any shape you want.


This product is for developers, Do not buy.
For the rug in the example:

I make products for myself. for the stuff I want and can't find in the catalog. If you want to buy my products, well, I am flattered. Let me congratulate you now on your good taste!
XOX
KD