This is code to perform perspective transform on a license plate. I want to replace a vehicle license plate. When I run this code, the license plate of the original vehicle is substituted with a black plate. The orientation calculation is true but I can’t understand why the plate is totally black with zero values.

this is a code to perform perspective transform on a license plate . i want to replace a vehicle license plate . when i run this code , the license plate of original vehicle substitute with a black plate . the orientation calculation is true but i can understand why the plate is totally black with zero values