Enable zooming in the crop views

[tuukka]

Problem

Currently, it's often impossible to crop a photo so that it would only contain something small such as a recycling icon or one-line ingredients. Similarly, it can be difficult to accurately crop something between two lines of text.

Proposed solution

There could be a zoom function in the crop view. After zooming in, it would be possible to crop more accurately as well as smaller areas.

Additional context

One additional reason for the need to crop a lot is the native photo UIs which switch to bad-quality macro photos if you try to zoom by moving the phone close to the product label.

Discussion thread on Slack: https://openfoodfacts.slack.com/archives/CSV2748EB/p1753715590252679

[monsieurtanuki]

@tuukka For the record the image needs to be "big enough", if not it'll be rejected by the server.

[Joeltabe]

Good day @tuukka Can i work on this

[monsieurtanuki]

Hi @Joeltabe!
There are pitfalls:

• we need 3 modes - crop a full image, recrop an already cropped image, crop a full image while erasing parts with a big marker
• we deal with "background tasks" - most of the time the result won't be a cropped image, but coordinates of the crop + rotation + coordinates of the "big marker" segments
• you'd have to deal with zoom in and zoom out
• you'd have to deal with the server minimum size requirements - e.g. 320x200 pixels
• we are not a crop app or package - the extra code for this feature must be maintainable for this minor feature

I wouldn't recommend working on this issue.