EXIF orientation info in PNGs isn't used for image-orientation: from-image
Categories
(Core :: Layout: Images, Video, and HTML Frames, defect, P3)
Tracking
()
People
(Reporter: e, Unassigned)
References
(Blocks 3 open bugs)
Details
User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_4) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.1 Safari/605.1.15
Steps to reproduce:
Go to https://ericportis.com/etc/PNG-EXIF-orientation/
Actual results:
The JPEG and PNG are rotated differently, even though they both have the same EXIF info (Orientation: Rotate 90 CW), and are both set to image-orientation: from-image;
Expected results:
They should display the same.
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Reporter | |
Comment 1•4 years ago
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Further findings: neither Safari, Chrome, or Firefox respects exiftool's default output, which appends EXIF to the end of a PNG. This is allowed by the spec, but seems to be incompatible with progressive rendering of partially-downloaded PNGs.
Safari does respect EXIF orientation info that appears before the image data, but Firefox and Chrome do not.
https://bugs.webkit.org/show_bug.cgi?id=210021#c4
https://ericportis.com/etc/PNG-EXIF-orientation/shuffling-chunks/
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Comment 2•4 years ago
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heycam: Will this be covered by any of your follow-up work related to bug 1607667?
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Comment 3•4 years ago
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Huh, I didn't even know that PNG supported orientation data. I found https://ftp-osl.osuosl.org/pub/libpng/documents/pngext-1.5.0.html#C.eXIf which defines the eXif table. The patches I'm working on don't add support for this, but it would not be too difficult to do so, at least if the table appears earlier than the image data. (I don't think our current image loading flow would handle the image size changing as a result of the orientation data later on.)
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Comment 4•4 years ago
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Because this bug's Severity has not been changed from the default since it was filed, and it's Priority is P3 (Backlog,) indicating it has been triaged, the bug's Severity is being updated to S3 (normal.)
Description
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