Solved by ptrblck in post #2 
              
              
                There seem to be some benchmarks showing a better performance for OpenCV, while others show some use cases where PIL is the winner (or Pillow-SIMD). 
Pillow-SIMD is a drop-in replacement for PIL using SIMD operations. 
You can find some benchmarks here, but as always with benchmarks I would be skept…