JPEG(JFIF) decoding. How to recover a damaged file?

Question

Programming

There is a JFIF Instagram photo with some bits "corrupted", as a result of which ~50% of the photo is displayed incorrectly.
How to find damaged areas and fix?
PS Hex-editor is.

Answer 1

There is an excellent FAQ on image recovery.
forum.ixbt.com/post.cgi?id=annc:23:28361

Answer 2

You can see the sources of the PhotoRec program as part of the testdisk package .

PhotoRec can handle some form of data fragmentation in JPEG file. Using the libjpeg library, it's able to check recovered data.

Answer 3

Damn, do you see the tags? I know that there are photo recovery programs. I do not need them.
I'm approaching this question from the perspective of a JPEG device. I want to know how it's done!