# Decompress a compressed jpg



## testcase

hope one of you out there can help. i have a bunch of jpgs that were taken off a canon digital camera, then (and i don't wanna know why...well. actually i do, but i think the answer might scare me...lol) were compressed for emailing using windows picture manager on a win 2000 pro O/S. now whenever i try to print one out, they look like...well, never mind, suffice to say they are now unprintable if i want them bigger than a thumbnail. is there software out there where i can print them out to 4 x 6 and still look good? thanks in advance for any help.


----------



## kaktex

Once compressed, they can't be uncompressed. 
The data is gone. 

If you can't get hold of the originals, it will take a lot of work to get anything decent. 
In Photoshop you can try enlarging, then using smartblur or one of the effect filters to try and smooth things out before printing. 
depends on the content of the photos, so more specific help would require seeing what you have to work with.


----------



## moper

When you made the compression change in Picture Manager, did you choose 'Save' or 'Save As'. 'Save' overwrites the original picture. Always use 'Save As', which creates a copy, preserving the original picture. 
Like Kaktex said, the original data in the photo is probably gone.
The safest way is to first create copies of the photos you want to send, and compress the copies for emailing.
Microsoft's 'Image resizer', is a very small program that is added to your right click menu. It always creates copies by default. Under the Advanced tab, make sure that "Resize the Original Picture" is unchecked. You can download it here:http://www.microsoft.com/windowsxp/downloads/powertoys/xppowertoys.mspx

Or, use XP's built-in photo e-mail. Good tutorial here, near bottom of page:http://www.geekgirls.com/windows_email_photos.htm
Note: XP does not change the size of your original photos; it merely creates copies in the new sizes and attaches those copies to your e-mail.

moper


----------



## testcase

sigh...somehow, i suspected it may be irreversable. i will immediately and henceforth institue a "save as" policy. there were far too many they did this to to make it worthwhile to try to spiff them all up in photoshop, but i suppose if i have any must-have pictures i can try that. thanks for the info


----------



## buck52

Has the card they were on been used since? If no they may be able to be recovered


----------



## testcase

been used and reused 20x over, unfortunately. that was my first thought, as it seemed the easiest route, and i for one am all for the easiest route lol


----------



## ChuckE

JPG format is not a compression format, in the typical sense of the word. It is a lossy format.

A compression format gives you the impression that uncompressing the file will re-constitute the data fully. Whereas a lossy format (as what JPG is) goes through a process where a level of detail is thrown away (it is lost) that allows for a much smaller file size end result.

How much detail is thrown away? that depends upon the program and the adjustment "dialed in" to set that desired level of loss. Hopefully, you just throw away the smallest of details that would never be typically missed, or noticed. But if the adjustment (as some programs can be adjusted) is set higher, there will be a more noticeable loss of detail - resulting in a smaller end file size.

But, as already had been mentioned. Once you make a JPG, to whatever level of quality, the detail lost is really lost. JPG is a lossy format.

As an aside, the algorithm that creates the JPG data is a pretty compact scheme. There is no repeating bytes or repeating combinations of bytes - which would really help if you were to then use a compression program to "squeeze" the data even tighter. So, it you were to run WinZip, against a JPG, chances are you will not notice any appreciable space savings - in fact, sometimes the file may grow a bit larger. All I am mentioning this for is so that you ought not waste your time in trying to compress JPG files. You can re-JPG them (as if that were a verb) to a higher level of quality loss, to make the end files smaller. But with the understanding of what I mentioned earlier. What you adjust to is lost.


----------

