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use pillow to save higher-quality jpg (w/o color subsampling)
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@LaserBorg
LaserBorg committed Mar 16, 2022
1 parent c09fb2a commit f334965
Showing 1 changed file with 3 additions and 1 deletion.
4 changes: 3 additions & 1 deletion utils/plots.py
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Expand Up @@ -467,5 +467,7 @@ def save_one_box(xyxy, im, file='image.jpg', gain=1.02, pad=10, square=False, BG
crop = im[int(xyxy[0, 1]):int(xyxy[0, 3]), int(xyxy[0, 0]):int(xyxy[0, 2]), ::(1 if BGR else -1)]
if save:
file.parent.mkdir(parents=True, exist_ok=True) # make directory
cv2.imwrite(str(increment_path(file).with_suffix('.jpg')), crop)
# use pillow to save higher-quality jpg (w/o color subsampling)
crop_pil = Image.fromarray(cv2.cvtColor(crop, cv2.COLOR_BGR2RGB))
crop_pil.save(str(increment_path(file).with_suffix('.jpg')), quality=95, subsampling=0)
return crop

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@LaserBorg LaserBorg commented on f334965 Mar 16, 2022 •
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opencv jpg compression does not support 'excellent' image quality since even the hightest quality setting uses 2x2 chroma subsampling (4:2:2), meaning that color information has only half resolution. This results in image artifacts on edges where colors change rapidly, especially when colors are highly saturated.
By using pillow, chroma subsampling can get disabled and therefore image quality raised.

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