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Re: [OM] Re:OT, Jpg, was: Lordly Com..........

Subject: Re: [OM] Re:OT, Jpg, was: Lordly Com..........
From: Richard Ross <richard@xxxxxxxxxxxxxxxxxxxxxxx>
Date: Wed, 13 Jan 1999 09:41:05 +0000
At 01:13 13/01/99 EST, you wrote:
>n a message dated 1/5/99 4:18:43 PM Eastern Standard Time,
>richard@xxxxxxxxxxxxxxxxxxxxxxx writes:
>
><< there is *no* deterioration of a digital image,
> provided of course it's not stored in a lossy format like jpeg when it will
> deteriorate each time it is opened and saved again. >>
>
>Huh??  :=)
>You have my attention now..please elaborate. And please share as to which
>format is "permanent"???


As I understand it, if you open a jpeg file and then save it again, you
will lose more information, and you'll lose more each time you do this.
The amount of loss depends on the compression ratio.

Formats such as TIFF, GIF etc use non-lossy compression, i.e. all the
information in the original is retained throughout the compression /
decompression process.

JPEG gives you nice small files for use on the web etc, but you will lose
information when you use it.  I didn't know until recently that the process
is not reversible - if you save, open, save, the two saved files aren't the
same....  AFAIK only the JPEG and MPEG formats suffer from this.

Regards
Richard


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