reveal jpeg blacked out section

winsumlusum

How would you remove blacked out section of a jpeg and see waht was undeneath it. Is it to do with metadata?

Torqay

winsumlusum wrote: »

How would you remove blacked out section of a jpeg and see waht was undeneath it.

You can't.

If you could, it'd be pointless to black out in the first place, no?

ScumLord

More than likely a corrupted which means that data is gone forever. Metadata is just tags and descriptions like what the picture is of, it has nothing to do with the data that makes up the actual picture.

bonzodog2

I don't know is will be of any help, I once cropped half of a photo to remove someone and leave just me in the pic, when I took memory stick to the Fuji machine in a pharmacy it initially showed me the origiinal complete picture as a thumbnal, but printed the edited version out as a fullsize image.

winsumlusum

Torqay wrote: »

You can't.

If you could, it'd be pointless to black out in the first place, no?

I think you can sometimes remove it depending on how it is done in the first place. There was a pervert once who put his image on the net with it swirled effect but it was able to be reversed and he was identified . is this not possible with blacking out some thing from a jpeg

ED E

winsumlusum wrote: »

I think you can sometimes remove it depending on how it is done in the first place. There was a pervert once who put his image on the net with it swirled effect but it was able to be reversed and he was identified . is this not possible with blacking out some thing from a jpeg

Thats totally different, he would have used a standard effect that could be reverse engineered. You cant do that when the data has been replaced with pure black.

Cant be done.

deconduo

winsumlusum wrote: »

I think you can sometimes remove it depending on how it is done in the first place. There was a pervert once who put his image on the net with it swirled effect but it was able to be reversed and he was identified . is this not possible with blacking out some thing from a jpeg

Swirling is different as almost all the information is still there, just moved about. With the right tools and a lot of time it can be possible (not guaranteed) to reverse it.

If something is blacked out its gone, as none of the previous information is still there.

winsumlusum

deconduo wrote: »

Swirling is different as almost all the information is still there, just moved about. With the right tools and a lot of time it can be possible (not guaranteed) to reverse it.

If something is blacked out its gone, as none of the previous information is still there.

even if the blacking out is done with say MS paint or similar just putting colour over the part blacked out?

AlmightyCushion

winsumlusum wrote: »

even if the blacking out is done with say MS paint or similar just putting colour over the part blacked out?

Yes, because when you save the image, all the data about what colour those pixels were before is gone.

winsumlusum

bedlam wrote: »

Sometimes an embedded thumbnail (if it exists) in a jpeg will not have been updated after the blacked out section was added to an image.

You can extract this thumbnail using jhead

jhead -st thumbnail.jpg original.jpg

That is what i meant. I did not know the term. Thanks everyone

would a thumbnail be a form of meta data?


where do i enter the code?

Torqay

winsumlusum wrote: »

I think you can sometimes remove it

Not with a jpeg, when blacked out and saved, all layers will be compressed into one new image, not a hope you get it back

yoyo

If an image is saved in a program like photoshop, and the black square is added, and the image saved without "flattening" I believe you may be able to seperate it. If flattened then the black square replaces the data underneath.
I do recall a security issue with documents issues to the public a while back by the UK government (I think it was) with certain details blocked out for security purposes. The images were never flattened so it made little difference once discovered

Nick

Torqay

yoyo wrote: »

If an image is saved in a program like photoshop

It depends on the file format not the software, and the OP asked about JPEG.

yoyo

Torqay wrote: »

It depends on the file format not the software, and the OP asked about JPEG.

I meant a jpeg saved in photoshop or any image editor that uses layers

Nick

winsumlusum

bedlam wrote: »

at a command prompt.

it didn't work said no such jpeg

bonzodog2

winsumlusum wrote: »

it didn't work said no such jpeg

substitute your filename for 'original.jpg' and make sure the current directory of the command prompt is the folder where the file is !

edit: put the jhead.exe in there too.

winsumlusum

ED E wrote: »

Thats totally different, he would have used a standard effect that could be reverse engineered. You cant do that when the data has been replaced with pure black.

Cant be done.

what would be the effect and how would it be reversed

Khannie

bedlam wrote: »

I believe Ed was referring to the swirl effect (or similar) in some image programs. There was a case several years ago where a paedophile had used the swirl effect to obscure his face thinking it would protect his identity and it backfired on him.

Owned in the face! Literally.

winsumlusum

bedlam wrote: »

I believe Ed was referring to the swirl effect (or similar) in some image programs. There was a case several years ago where a paedophile had used the swirl effect to obscure his face thinking it would protect his identity and it backfired on him.

that is the one i was trying to think of
I get error no such file in file xxxxxxxx.jpeg. That means there is no thumbnail?

bonzodog2

It means it can't find the filename you gave

examples for success,no thumb in file and missing file:

C:\Documents and Settings\dell\My Documents
>jhead -st thumb1.jpg hasthumb.jpg
Created: 'thumb1.jpg'

C:\Documents and Settings\dell\My Documents
>jhead -st thumb2.jpg nothumb.jpg
Image contains no thumbnail

C:\Documents and Settings\dell\My Documents
>jhead -st thumb3.jpg nosuchfile.jpg

Error : No such file
in file 'nosuchfile.jpg'

ScumLord

yoyo wrote: »

I meant a jpeg saved in photoshop or any image editor that uses layers

Nick

Jpegs don't have layers. If it's saved as a jpeg it's a flat image and what you see is what you get. I think tiffs can save layers but for the most part if it's not saved as a photoshop file the file is flattened into a single layer.


Jpegs are also highly compressed so they have very little data, if your editing in photoshop you save as a photoshop file and save a copy as a jpeg for final output onto the web.

winsumlusum

So if i post a jpeg to a site and blacken out say a car reg no one can unblacken it?

bonzodog2

If you are that concerned, copy the image after blacking out the reg to a new file and upload that.

ScumLord

winsumlusum wrote: »

So if i post a jpeg to a site and blacken out say a car reg no one can unblacken it?

No hope. Jpegs are made to have as little data as possible so they're as small as they can be. From a editors point of view they don't even have enough data to make them any use for further editing. If your taking an image off the web it's pretty much the lowest of the low when it comes to picture quality and data content.