repairing corrupted jpg

[osullic]

I may be wrong, but I believe that when JPEGs which contain an embedded thumbnail are viewed in Windows Explorer, it's the embedded thumbnail that is displayed (and used to generate the thumbs.db file), not the main image itself.

So if you have JPEG files that are partly corrupted, but it's only portions of the main image data that are corrupted and not the embedded thumbnail, then you can have this situation where the thumbnail displays fine in Explorer, but the image is corrupted when opened in Image Editing software.

This site claims that many corrupted JPEG files can be fixed:

http://www.impulseadventure.com/photo/fix-corrupt-jpeg-photo.html

[matera]

I recently went through some odd exercises with an MP3 player that demonstrated similar-seeming problems. Files were on it all right, but it was hard to access them. After some online research, and poking around with the player in different computers, I learned a little about the different ways in which Windows might view an external device.

No files might indeed mean that there are none or that they have been deleted - or it might mean that Windows configuration for this device is wrong. It might be trying to see it in the wrong way. It is as if a CD were being viewed as a floppy - to use a badly stretched analogy - or trying to view files on an NTFS formatted hard drive with an old Windows98 DOS boot floppy.

I am not saying that this is the case here, only dropping in the information in case someone else has issues with reading files on a card or device.

Did you recover all of the files in a single operation? If so, you might try using the recovery procedure again for just the files that came out bad the first time. They might still be all right on the card, but got messed up because of the amount of data being processed. Sounds odd, but it can happen. On the other hand, the files might have gotten cross-linked when the camera glitched. However, after looking at the attached specimens, I am inclined to think that it is a case of incomplete recovery. The whole image - what there is of it - looks exactly like what sometimes happens when I am downloading a large image from the internet and the process is interrupted. The thumbnail is fine in both cases. I do not use Windows Explorer as an image viewer and have forbidden the creation of the thumbs.db, but there are other ways. I used 11View, which shows the embedded thumb.

I would try again, and also make more attempts to view the card with a file manager. Maybe it would work better - be recognized by Windows better - in the camera...?

I haven't seen everything, but I'll try anything

[Sam_Zen]

2 osullic
I didn't know about embedded thumbnails in a JPEG file, because I don't do much camera things.
But I think now, you got a point here about a correct thumbnail view, but still a corrupted full image.
As stated on your very interesting URL at the chapter : "But the JPEG Thumbnail is OK!".

Another remark there, related to this thread :
"Why do JPEGs get damaged?
* Photos were deleted or formatted & a "recovery" utility was used"

And a quite logical advice for camera-users there :
"For memory cards, periodically Format the card instead of using single-file delete or delete-all."

These two "convar" files obviously can't be recovered, because they are taken out of their context.
But this program JPEGsnoop 1.2.0 by Calvin Hass seems very useful anyway. As analyzer.
And the site has all kinds of good technical information about these matters.

2 matera
Thanks for the 11View app. At least to be used as a viewer for inside thumbnails.

looks exactly like what sometimes happens when I am downloading a large image from the internet and the process is interrupted

Exactly. An old problem. I've never been able to correct these grey areas when it happened.
I guess it has something to do with a discrepancy between the filesize in pixels, which is declared early in the file,
and the position of the EOF pointer. And JPEGsnoop introduces another one : the EOI pointer.

I do not use Windows Explorer as an image viewer and have forbidden the creation of the thumbs.db

Right on, and can you tell me how to forbid the creation?
I would like to know how to advice people to disable this horrid construction to make some hidden file.

This problem is partially caused by a growing trend in file managing to indicate a file with its own thumbnail.
Instead of by some efficient small icon.

Your advice to start all over from the camera stage seems a good one.
This is where the correct recovery should take place, not with some copy on another device.

[matera]

My goodness, I just added JPEGsnoop to my toolbox, don't know how it hid from me before

The embedded thumb escapes undamaged because it is very near the beginning of the file. It seems that computers eat files like cats eat mice, starting with the head(-er), so it is always the tail that gets left out in a botched copy or move. The thumb can be extracted by an obsessed person with a hex editor.

I have a sentimental attachment to 11view, one of the programmers is one of my favorite musicians.

[Sam_Zen]

Nice powerful compositions there indeed.
Maybe 'Matera the Mad ' should warn Andrey Pivovarov, that his site is open to 'downward' navigation.
Take http://www.efenstor.net/mp3s/voice_of_peregrination/ and remove the album-title from the URL..