[RFC] Refactor image handling

[J0WI]

There are various tickets about poor image handling in Nextcloud.

• Replace Imagick with something better #13099
• Allow more preview formats #13552
• Jpeg use imagick #16158
• Send images to Imaginary docker to generate previews #24166

Nextcloud uses the OC_Image wrapper which uses GD. But GD is slow and does not support formats like SVG. That's why some modules (avatar, preview and theming app) have implemented their own image handling.

This draft aims to replace the legacy OC_Image class with a generic Image class and a set of compatible backends using GD, Imagick, Gmagick or Vips. It turned out, that the IImage interface itself does not provide all methods and not all of them are meaningful for all backends (notably the obsolete GD resource). There's also no simple way to add additional file format support.

An alternative approach would be to pull a high level image library like intervention/image or imagine/imagine.

The goal is, to provide a generic image handling that uses the fastest backend and all common and modern file types available on the host. And last but not least, to replace direct Imagick usage in avatar, preview and theming app and finally deprecate the legacy OC_Image class.

[J0WI]

@blizzz@szaimen I've seen you listed this on beta releases, but I need some feedback on this RFC before I continue here.

[CarlSchwan]

Nice work, I'll review it tomorrow

[icewind1991]

Overall a great step forward

[github-advanced-security]

Found 100 potential problems in the proposed changes. Check the Files changed tab for more details.

[github-advanced-security]

Found 100 potential problems in the proposed changes. Check the Files changed tab for more details.

[sorbaugh]

Hello @J0WI, it seems that some of the tickets you mentioned in the original comment have already been addressed so some the points have been addressed. I'm reopening this complex topic and would like to treat this as an "Overview" issue and maybe rescope it to the remaining open issues 🚀

[github-advanced-security]

Psalm found more than 20 potential problems in the proposed changes. Check the Files changed tab for more details.

[susnux]

Hello 👋
currently here have been no activity in the last years.
If this is still actual feel free to reopen the pull request and resolve the conflicts so we can incorporate it into Nextcloud.
Thank you very much for your contribution!