feat: Improve EXIF dimension tags handling

[patrickfournier]

This pull request improves how EXIF tags are handled when processing images, especially regarding image dimensions, and enhances the related test coverage. The most important changes can be grouped as follows:

EXIF Tag Copying and Image Dimension Handling:

• The plugin now updates the ExifImageWidth and ExifImageHeight tags to match the dimensions of the transformed image when copying EXIF tags. This ensures that metadata accurately reflects the new image size after processing.
• The EXIF tag copying logic updates dimension tags only if they existed in the source image, preventing the addition of these tags to images that originally lacked them.

Testing Enhancements:

• Added new tests to verify that dimension tags are correctly copied and updated when present, and that they are not added to images that lack them.

Process and Logging Improvements:

• Changed the EXIF tool subprocess so that its stderr is redirected to stdout, and improved logging by outputting the exact exiftool command used for debugging purposes.

Documentation:

• Updated the documentation to explain the new behavior regarding EXIF dimension tags.

Minor Edits:

• Minor formatting improvements in the README for better readability.

[justinmayer]

Seems sensible to me. Any thoughts, @minchinweb?

[minchinweb]

I'm just able to do a "desktop" (ok, phone) review at the moment, but it looks good. Thanks for the PR, and thanks for including tests!

I was vaguely aware that Exif dimensions could mis-match the "physical" dimensions, as it came up on Immich's list of "Cursed Knowledge", bit hadn't drawn the connection it could affect us here.

(For future reference,) Is there a reason not to add these dimensions to images that don't already have them?

Also, should add a note to our list of "known issues" that Exif and "physical" dimensions will drift of ExifTool isn't installed?

[patrickfournier]

I do not add the EXIF dimension tags because I don't want to "pollute" the image with tags that were not there originally.

If ExifTool is not installed, the tags (including the EXIF dimension tags) will not be copied from the original image, so there is no possibility for them to drift from the correct value.

[minchinweb]

Everything looks good to me! @justinmayer will you merge this?

[justinmayer]

Yes, indeed, I’d be happy to. Thank you for taking a look — I appreciate the extra set of eyes.

@patrickfournier: Many thanks for your work on this! ✨