Re-implement pHash comparison using cv2. Drop imagehash+Pillow
#635
| Job | Run time |
|---|---|
| 3m 27s | |
| 1m 47s | |
| 3m 22s | |
| 1m 50s | |
| 1m 37s | |
| 2m 18s | |
| 1m 18s | |
| 2m 6s | |
| 17m 45s |