This Is Annoying!!! Argh!!!! Stop It Now!!

[Ragdoll]

Please DON'T COMPRESS .png images. If you do that, your texture archives will get twice larger... Please select the lower compression level (store) instead.
Thanks.

 

[Sirmatto]

Please DON'T COMPRESS .png images. If you do that, your texture archives will get twice larger... Please select the lower compression level (store) instead.
Thanks.

Compressing something that is already compressed will yield you with an archive relatively the size of the original file...

 

[Ragdoll]

If you try it, you'll see it often results in a larger result, since the file is already at the minimal size, and the compression software can't notice that.

 

[Poobah]

Actually, a reasonably large archive of PNG images will be about 24/25 times the unpacked size, when compressed with a popular archive format such as ZIP or RAR.

A small archive of PNG images will be a few KB larger. However, it's more convenient to pack files for easy transportation via the Internet.

Here's a little test I've just done using the "Zelda Final Update.zip" archive:

ORIGINAL   ZIP      RAR     7-ZIP    STORED
 51.9MB   49.8MB   48.7MB   38.4MB   52.3MB

Although compressing a single compressed file is illogical, compressing multiple compressed files using a global dictionary -- as opposed to one per file -- is quite efficient, which is why 7-zip is significantly better than other archivers when compressing large amounts of files.

If you try it, you'll see it often results in a larger result, since the file is already at the minimal size, and the compression software can't notice that.

PNG files are not the minimal size. The true minimum compression size can usually only be obtained via compressing by hand or an extremely slow brute-force compressor.

 

[Ragdoll]

Yeah... I was about to suggest 7-zip, since it has superb performance when compressing similar files.