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How can I compress my files as much as possible?


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#1 funnytim

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Posted 21 January 2009 - 03:22 AM

Hey all,

I have a number of pictures (~ 395mb total) that I would like to compress to as small as possible.


Using WinRAR, I only managed to compress it down to 377 MB in RAR format. (ZIP was even bigger)
With PowerArchiver, it only compessed down to 376mb in 7z format.

Both compressions I tried were done using the maximum compression setting , but it was only able to compress ~20mb.


Is it possible to somehow (either in the above apps, or in another app) to compress it even further? A week ago my friend was able to compress a 600MB game to 300MB using WinRAR in rar format , but I can't seem to be able to compress to ~ the same ratio he did).

Thanks!

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#2 Platypus

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Posted 21 January 2009 - 06:30 AM

Most common image formats are already compressed, eg .JPG, and compressing them a second time achieves little.

Many other file types like you would find comprising games etc are not pre-compressed, and their size can be reduced greatly.

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#3 funnytim

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Posted 21 January 2009 - 11:25 AM

So then there is really no point in ziping images?

But when I do compress formats such as games, etc it is done the same way right (ie. use WinRAR / others to max. compression) ?

#4 Platypus

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Posted 21 January 2009 - 05:18 PM

So then there is really no point in ziping images?

You won't gain much, but I can think of a few reasons:

1. Only one large file to deal with.
2. You will gain some storage space. Not only from the small amount of compression, but also from slack space (the unused cluster space at the end of every file) not being wasted storing dozens or hundreds of small files. The greater the number of smaller files, the more you save by having them in one large file.
3. You can password protect the .ZIP if you don't want someone to be able to access your pictures if they find your backup.

Potential disadvantages:

1. If a single image file corrupts in your backup of copied individual files, you lose one image. If a compressed archive of many files corrupts, you may not be able to access any or a portion of the files it contains. Ditto if you forget the password for a protected archive.
2. If you use maximum compression, the time taken to create the archive then transfer it to a backup drive is that much greater than just copying the individual files across.

But when I do compress formats such as games, etc it is done the same way right (ie. use WinRAR / others to max. compression) ?

Yes, compression is well understood these days, differences between the results from different programs will be small, and if you select maximum compression, you can be sure that there's little you could do to make it any better.

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#5 funnytim

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Posted 21 January 2009 - 07:53 PM

Thanks a lot.

Also, I noticed you said here:

3. You can password protect the .ZIP if you don't want someone to be able to access your pictures if they find your backup.

which leads be to ask another question... I'm planning on encrypting and backing up some pictures online. Since its being uploaded to a remote server I want to make sure my pictures + files are as secure as possible, as the remote server doesn't offer enhanced security (if at all) themselves.

Would using a encryption software such as http://www.axantum.com/AxCrypt/
be more powerful than the ones built into archivers, such as PowerArchiver, WinRAR , Winzip, etc?
(AxCrypt has a feature where you can specify the need for a key file to be able to unlock a encrypted file, which seems nice)


Thanks again.

#6 muuji

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Posted 23 January 2009 - 12:56 AM

try using irfanview (or something similar) and then zip or rar them. when i want to send a number of photos by email, i first compress them using irfanview and then zip them - not to further compress them, but to avoid having to attach each photo to the email separately.
Muuji

#7 SCPics

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Posted 24 February 2009 - 01:02 AM

I know that conventional wisdom says you can't compress a jpg because it's already compressed format but you can. I found a program call Shrink that compresses jpgs with no loss of image quality.

Funnytim, you said you reduced 395mb with winrar to 377mb. With Shrink, I reduced 366mb worth of pictures to 125mb! With compression this great, I can save two copies of my pictures and still save memory space.

I was skeptical about the image quality so I checked some of the images after decompression at 15x magnification. I couldn't find any difference between the decompressed file and with the original - AT ALL. The best part is it's only 10 bucks to register. You can find it here http://www.sharewaregenie.com/ShrinkReview.php.

I hope this helped.

#8 funnytim

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Posted 25 February 2009 - 09:37 PM

Thanks that looks like an interesting program ;)

Would you happen to have a link to the official website? (That site only seems to be a review). Thanks again

#9 SimoneK

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Posted 28 February 2009 - 10:26 AM

the vendor is Miliki and their site is not working atm




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