compress pictures

[Jim March]

Put another way: some graphic file formats are inherently compressed:
.JPEG, .GIF and .PNG for starters.

Some aren't, such as .TIF and .RAW.

If they're NOT already compressed, then .ZIP or other archive
compression will help.  If they're compressed already, nope...won't do
squat.

Another problem with .ZIP archives or the like: a small disk error in
the middle of the archive can make the whole stack blow up, whereas if
it's just a folder with a bunch of individual files, that same single
error would only take out one picture.

Jim

On Wed, Nov 30, 2011 at 5:07 PM, Matt Graham <danceswithcrows at usa.net> wrote:
> From: Michael Havens <bmike1 at gmail.com>
>> I want to compress a bunch [of] pictures to put a bunch on my zip
>> drive. What is the best program to use?
>
> Most image formats are already compressed in some way.  JPEG, GIF, TIFF, and
> PNG are almost always compressed.  Compressing an already-compressed data set
> doesn't usually buy you very much at all, 1 or 2% if that.
>
>> I was thinking 'zip' would be good
>
> See above.  zip will work, though tar combined with bzip2 (or xz/lzma) may be
> more space-efficient at the cost of it taking longer to compress and
> uncompress the data.  That's "tar cjf images.tar.bz2 images/" or "tar cJf
> images.tar.xz images/" to create compressed tarballs of everything in the
> images/ dir.  Replace "tar cjf" with "tar xjf" to uncompress.
>
> --
> Matt G / Dances With Crows
> The Crow202 Blog:  http://crow202.org/wordpress/
> There is no Darkness in Eternity/But only Light too dim for us to see
>
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