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Return rgb when rgba is loaded #734
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yuyu2172
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Hakuyume
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Nov 26, 2018
chainercv/utils/image/read_image.py
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| @@ -22,6 +22,11 @@ def _read_image_cv2(path, dtype, color): | |||
| # reshape (H, W) -> (1, H, W) | |||
| return img[np.newaxis].astype(dtype) | |||
| else: | |||
| # alpha channel is inclued | |||
chainercv/utils/image/read_image.py
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| if img.shape[-1] == 4: | ||
| bgr = img[:, :, :3] | ||
| alpha = img[:, :, 3:] / 255 | ||
| img = bgr * alpha + 255 * np.ones_like(bgr) * (1 - alpha) |
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I think there are three options.
- just ignore alpha channel
- blend with black image
- blend with white image
Why do you choose 3.? Personally, I prefer 1.
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This is because the alpha channel contains meaningful information (for some part, the value is in (0, 1)).
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Is 2 better?
I thought 3 was more natural
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Hakuyume
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Hakuyume
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Sometimes,
cv2.imreadreturns(H, W, 4)array (e.g., the image below).It seems that this behavior is dependent on the build of cv2.
The bug occurred with the
cv2installed using anaconda, but the same problem did not occur forcv2installed with apt.EDIT:
Alpha channel extracted by
img = cv2.imread(path)[:, :, 3]RGB extracted by
img = cv2.imread(path)[:, :, :3][:. :. ::-1]PIL
f = Image.open(path); img = f.convert('RGB');