fix: convert RGBA PNG to RGB in labelme2coco.py#1830
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wkentaro
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Mar 6, 2026
RGBA PNGs (4-channel images with an alpha channel) cause an OSError when imgviz.io.imsave() tries to save them as JPEG, since JPEG does not support an alpha channel. Strip the alpha channel by slicing to [:, :, :3] after loading the image array when the image has 4 channels. Closes #1653
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Summary
When
labelme2coco.pyloads a PNG with an alpha channel (RGBA, 4 channels),imgviz.io.imsave()fails with anOSErrorbecause JPEG format does not support an alpha channel.Fix
After loading the image array, strip the alpha channel when the image has 4 channels:
Changes
examples/instance_segmentation/labelme2coco.py: drop alpha channel for RGBA images before savingCloses #1653