P: Exported JPEGs missing mandatory PixelXDimension and PixelYDimension EXIF tags

[johnrellis]

JPEGs exported by LR are missing the PixelXDimension and PixelYDimension EXIF tags (image width and height), required by EXIF Version 2.32 (and prior versions going back to at least EXIF Version 2.2, 2002).  This trips up software libraries expecting to find those mandatory tags. 

Tested on LR 12.0.1 / Mac OS 12.6.1 and LR 6.14 / Windows 10.

To reproduce:

1. Export any photo from LR as a JPEG.

2. Run this Exiftool command on the exported JPEG:

exiftool -a -G -EXIF:ExifImageWidth -EXIF:ExifImageHeight file.jpg

(Exiftool calls PixelXDimension and PixelYDimension "ExifImageWidth" and "ExifImageHeight".)

Here's the relevant section from the EXIF Version 2.32 specification (page 44):

Note that Photoshop correctly writes those tags, though it also writes EXIF:ImageWidth and EXIF:ImageLength, which violates the standard in a different way (page 28):

[FlickRick]

I can not get Lightroom to export any pixel dimensions.

I have all metadata export enabled. When I use a Windows EXIF viewer, no dimensions are present. When using the JS EXIFR package, same thing, nothing is present.

Other users are having this same issue: https://www.reddit.com/r/Lightroom/comments/yheq9r/image_dimensions_not_included_in_exif_data_for/

[johnrellis]

All the export formats require the image pixel dimensions to be included -- it's not possible to have a JPEG, for example, without specifying the width and height in pixels.  Otherwise, how could the image be displayed by viewers?

Attach one of the exported JPEGs here and we'll put it under the microscope.

[FlickRick]

Thanks, here's a photo I recently exported:

https://drive.google.com/file/d/1LdEt7h51nJeFdprBnvEI9nyzfaDOEwpB/view?usp=sharing

[FlickRick]

And here it is attached, just in case GDrive removes any metadata.

[TheDigitalDog]

Well something seems wrong with your EXIF viewer because the image you provided has all the necessary dimensions present as metadata:

[FlickRick]

You're correct, the dimensions do show up, in certain applications.

I'm using EXIFR to get the metadata, for some reason the dimensions are blank for any photo that I test from Lightroom. Here's the link for the EXIFR playground.

https://mutiny.cz/exifr/

[TheDigitalDog]

This isn't a Lightroom Classic issue. Clearly, LR exports the metadata. You'll have to take up the issue with whoever is making this EXIFR product, it seems like a bug....

[johnrellis]

I did a deep dive on this.

LR isn't strictly conforming with the EXIF 2.32 specification, though not in the way incorrectly assumed by that Reddit thread.

For compressed JPEGs, the spec requires the width and height to be recorded in the EXIF tags PixelXDimension and PixelYDimension (page 44) and in the JPEG marker segment SOF0 (page 89).  LR writes the latter but not former (without the marker segment SOF0, no reader would be able to display the image).  I filed a bug report on this:

https://community.adobe.com/t5/lightroom-classic-bugs/exported-jpegs-missing-mandatory-pixelxdimensi...

But note carefully that the EXIF tags mentioned by that Reddit thread, EXIF:ImageWidth and EXIF:ImageLength, should never be recorded in compressed JPEGs.  The spec says (page 28), "In JPEG compressed data, this tag shall not be used because a JPEG marker is used instead of it." (Photoshop, and probably other apps, incorrectly writes those tags for compressed JPEGs.)

The EXIFR library calls PixelXDimension and PixelYDimension ExifImageWidth and ExifImageHeight. Apparently, EXIFR doesn't read the JPEG marker segment SOF0 (the only place that LR writes the width and height).  It probably should.  

Instead of EXIFR, use Exiftool, which reads the width and height from the JPEG marker segment. In general, I rely on Exiftool as the most authoritative tool/library for examining photo/video metadata, and I incorporate it in my LR plugins.

[Lumigraphics]

All JPEG files are compressed. However, JPEG compression is a different thing, for example TIFF layers can use JPEG compression.

Also, there is NOT a standard for how JPEG compression is done, only how it is decompressed. That allows newer compression methods to be used as long as the finished file can be properly opened.

[johnrellis]

"All JPEG files are compressed"

Right, I was imprecisely copying the usage from the EXIF spec, which frequently uses the terms "uncompressed data" and "JPEG compressed data".  The spec encompasses images with uncompressed RGB data, uncompressed YCbCr data, and JPEG compressed data.

Files with JPEG compressed data should have the PixelX/YDimension tags and should not have ImageWidth/Length tags, and vice versa for files with uncompressed data.

[Rikk Flohr: Photography]

Missing status