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EXIF orientation info in PNGs isn't used for image-orientation: from-image

(bugzilla.mozilla.org)
94 points justin-reeves | 1 comments | 21 Nov 25 13:29 UTC | HN request time: 0s | source
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rkagerer ◴[21 Nov 25 16:27 UTC] No.46005944[source]▶
Orientation in EXIF was an ugly hack and we're living with its fallout today.

Cameras should have just rotated the actual image pixels when saving, instead of cheating. If that's too slow, implement it in hardware, or schedule a deferred process and don't let the images be exported until that's done.

replies(3): >>46006024 #>>46008635 #>>46009719 #
OptionOfT ◴[21 Nov 25 20:31 UTC] No.46008635[source]▶
> Cameras should have just rotated the actual image pixels when saving, instead of cheating. If that's too slow, implement it in hardware, or schedule a deferred process and don't let the images be exported until that's done.

What if I want to rotate an image by 90 degrees because my camera didn't correctly detect up & down?

To my understanding rotation is lossless, where as moving the data will incur quality loss (except for certain exceptions).

replies(1): >>46010131 #
1. lxgr ◴[21 Nov 25 23:05 UTC] No.46010131[source]▶
JPEG rotation can be lossless for certain image dimensions (multiples of 8 or 16 pixels respectively, depending on chroma subsampling).

I suppose it's no coincidence that the native output format of many sensors (or ISPs, to be precise) is divisible by 16 in both width and height.