On Sun, 2003-02-02 at 09:25, John Richard Smith wrote:
> Michael Adams wrote:
> The purpose is to make a permanent store of old photos in a manner where
> the images do not
> fade and deteriorate with time. On the whole I'm not displeased with
> .jpg , I tried .pnm file format
> and although the data is of a higher order of magnitude of visual
> quality you get that at the price of
> enormous file sizes, something anywhere between 15 and 50mb per image.
> Whereas a .jpg file
> gives a good enough image file in the region of .5mb to 2.5mb, and I
> find this acceptable . It means
> I can later write a very large number of image files to one cd for
> permanent record.
>
For archiving purpose, you can achieve both high quality and high
compression using tar and gzip or bzip2.
tar -cjf filename.tar.bz2 filename.pnm
Compressed size to original size ratio will vary, being 1/3 a rough mean
value for raw pnm and bzip2.
Only drawback is that you will need to decompress it before using any
graphic program.
HTH
> In addition, thinking of the future , as technology changes, as it
> always will, I cannot believe that the
> means will not flow to change these .jpg image file cd into something
> else, what ever that may
> in the end up being, who knows. While, if I use .pnm files I question
> the wider acceptability of this
> format and whether the same convertability may not be true as explained
> in regard to .jpg.
>
> John
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