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     áòèé÷ :: Filmscanners
Filmscanners mailing list archive (filmscanners@halftone.co.uk)

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filmscanners: Compression Formats (CD Storage)




Lossless:
ie when you uncompress you get an exact of the original
TIF LZW - compression 5-20% for photo images
    PNG - compression 10-40% for photo images

Note that PNG will always be smaller due to
a more efficient algorithm.

Original: 24532 Kb = 2500x3300@24bit
 TIF LZW: 20336 Kb = 17% smaller
     PNG: 16348 Kb = 33% smaller

Lossy:
ie when u uncompress you get less than the original
but much better compression
 JPG@15%: 1440 Kb
 JPG@25%:  990 Kb
     GIF: 6675 Kb
   PNG@8: 5172 Kb

Note that JPG uses 24 bit colour and throws away data
that the human eye/ brain ignores to some extent.
GIF uses a 256 colour indexed system - for photo images
it is terrible. PNG using 256 colour compresses smaller
than GIF due to a more sophistcated algorithm.

Conclusions (please contribute):
TIF LZW is fine, but PNG is a lot better. Both are lossy
but TIF has been around longer, and thus is better 
supported. PNG is realtively new, but it is open-source
meaning that any software developer can use its code,
which is freely available ... so if its not there then
complain.

Forget GIF. Its wayyyy too lossy for photo images. For
low colour images (<256) it is fine, but PNG does a
better job than GIF anyway for this type of image.
Most browsers support JPG/GIF/PNG.

PNG offers support for 8/24/48 bit colour, with better
compression than TIF (significantly).

Personally. I store in PNG format on CD, with a nice
auto generated index.html file displaying thumbnail
JPG images which lead to medium size 800xAAA JPG images
and large 1400xAAA images. This gives me a full monitor
view and a web capable view.

bert
unoffcial Filmscanners archive at:
http://phi.res.cse.dmu.ac.uk/Filmscan/




 




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