A small bug when preprocessing the VFHQ dataset

[lxycopper]

Good work and congratulations!

I came across a small bug when I preprocess the VFHQ dataset with the scripts scripts/preprocess_dataset.py. It is about reading files:

ibpng error: Read Error
cv2.error: OpenCV(4.8.1) /io/opencv/modules/imgproc/src/color.cpp:182: error: (-215:Assertion failed...

That's because there is an image in the VFHQ dataset which has a transparent part.

The image's location is at
"VFHQ_dataset/Clip+8jwB6QSzjy4+P0+C1+F17517-17845/00000184.png"
simply removing this image or adding a judgement sentence at line100-line101 in scripts/preprocess_dataset.py can fix this issue.

if img is None:
    continue

Hope this can help someone.

[Zejun-Yang]

Oh yes, excluding the invalid images is crucial. Thank you so much!