Parzival
Thanks for the hint about PNG. I came across this format only when I
started using Fireworks, and I thought it was a bit of a distraction.
However, I now see that it is smaller than TIF.
Chris
On 1 Apr 2004, at 20:44, Parzival Herzog wrote:
>
> On April 1, 2004 11:45, Chris Barker wrote:
>> When you use this format, you have the choice of qualities or
>> 'lossless'. I should have expected that to fulfill its description.
>> Are you telling me that this dialogue box is an out and out liar? ;-)
>
> The, JPEG 2000 file format includes a lossless option., in which
> residual
> error from the main image compression result is also stored. Of
> course, if
> your program is not doing it correctly, then its dialog box may indeed
> be
> lying. Its easy to check though: Compress your image file with Jpeg
> 2000 then
> expand in your image processing program, subtract expanded image from
> the
> original, and you will get the error image. This will appear black
> until you
> expand its (hopefully minuscule) tonal range to full scale. Lossless
> will
> stay black, as there is no tonal range.
>
> Try this with the same image compressed to the same compressed file
> size,
> using jpeg and jpeg2000. You should see that for most photographic
> images
> jpeg2000 is indeed much better, and the error is generally well below
> the
> noise inherent in the photographic image (although it is not uniformly
> distributed,) so that going "lossless" is practically speaking, a
> meaningless
> waste of storage and processing. Some artifacts in digicam images with
> Bayer
> mask sensors will greatly exceed jpeg2000 artifacts at reasonable
> compression
> ratios.
>
>
<|_:-)_|>
C M I Barker
Cambridgeshire, Great Britain.
+44 (0)7092 251126
ftog at threeshoes.co.uk
http://www.threeshoes.co.uk
http://homepage.mac.com/zuiko
... a nascent photo library.
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