Add a way to crop the scanned picture (or automatically crop it)

[Massedil]

Exporting as an image (#46) will help to crop with another app, but it could be cool to have directly this option in the app.

Here is the top of a scanned document where croping could be interesting to remove the wavy edge.

Thanks for you app !

[pynicolas]

As I tried to explain in a blog post, I would really like to keep FairScan simple and to avoid manual tweaks. I strongly prefer to work on the automatic processing so that all users get great PDFs easily.

[adrianinsaval]

that's great but it's basically impossible to make automatic detection work well on all situations, I don't want a bloated app either but sometimes you really do need to tweak stuff. In my case I'm scaning pages that are permanently attached to a folder that is larger in size than the pages, the edge detection failed often and included the folder or contiguous pages, it would be great if I could tweak the cropping in those cases

[pynicolas]

@adrianinsaval I totally understand that there are cases where automatic detection struggles. For now I'm still trying to keep the app fully automatic, so manual tweaking isn't something I plan to add.

If you have an example image where the current detection fails, feel free to mail it to me (contact@fairscan.org). It helps me understand the edge cases and improve the model over time.

[PhilLab]

@pynicolas it is a good goal to have everything automatic and easy to use. However, put it like this: if the automatic detection fails, you spend a lot of time recapturing, trying to convince the system of a better crop. Assistant Systems without a way to manually correct errors (which will happen) have a hard time convincing users.
To be honest - even if your app has by far the best CV of all open source scanners, I have stopped using it for precisely that reason. I felt too dependent on an algorithm performing well.

Would you accept a UX flow which adds the crop correction as an optional step in the end, e.g. when clicking on the thumbnail? In a way which keeps it entirely out of your way if you are not interested in it?

P.S.: I took note of your request for sending failed document detections. In case I notice it again, and it is a non-sensitive document, I will send you the image.

Edit: the ticket #72 is closely related

[PhilLab]

@pynicolas coming to which - if I am using FairScan and have a failing scan, how can I extract the original image to share with you?

[pynicolas]

@PhilLab There's currently no way to retrieve the last captured image in FairScan.

For now, the only workaround is to share a photo taken in similar conditions, if that's possible for you.

I've opened a separate issue to track this limitation and possible improvements around accessing the captured image, but there is no timeline for it at this stage.

[BerenLuth]

I agree that even if you try your best to make the algorithm perfect (and I appreciate it a lot), in real world scenarios there is too much variation.

The algorithm works really well now in ideal scenarios, with a flat background, good lights, flat paper, and so on.
But, for example, in my case I usually have to scan receipts on the fly, they usually tend to roll on themselves a little bit, and I don't always have a flat surface to put them on. And it gets really frustrating when i finally see the perfect green rectangle capture preview, just to completely skew the exact moment I try to take a picture :(

The option to manually adjust the corner would be great. It doesn't necessarily "bloat" the app, it can be a long press to the thumbnail after the picture is captured, or it can even be disabled by default and enabled in the settings as an "advanced feature".

[ki9us]

For small receipts in good lighting, FairScan is great. For long receipts, it never crops correctly, making it unusable. Any long (tall) receipt will work to reproduce.

Like others, I think you could spend your whole life improving the auto-crop and still have cases where it just doesn't work. What if the lighting is bad? Paper is crumpled? White background? Different color paper? Jagged edges? Round paper?

Users just want the ability to adjust the cropping "in post", and we always will.