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Re: filmscanners: Lossless JPEG's? was Hello



you might be interested in lurawave plug-in into irfanview. it can compress
images up to 4k x 4k pixels. you have to have a fast computer though. the
algorithm is based on wavelet compression (see jpeg2000 specs). hardware based
decoding chips are at least two to three years away.

lemuel ragasa


"Mark T." wrote:

> At 04:06 AM 21/10/01 -0600, Bill wrote:
> >...
> >o The JPEG standard includes a lossless setting.  Photoshop 6 supports it:
> >set the quality level to 12. it will compress to, say, 1/3 of the original
> >size.  JPEG only supports 24-bit images.
>
> G'day Bill.
>
> I had never heard of a lossless JPG, so I checked the JPEG FAQ, which
> basically says that there *was* an early version of a lossless JPEG, but it
> never took off.  They also referred to a new standard called JPEG-LS - is
> this what you meant?  I couldn't see anything about it in the PS Help file,
> but I only took a quick look.  I would be most interested if PS6 really
> does supprt a lossless JPG..  As far as I knew, the main players were/are:
>
> TIFF
> - 48-bit, lossless, large files
>
> TIFF with LZ compression
> - As above but files can be much smaller (esp if image is not grainy or
> detailed), eg typically 1/2 to 1/5 original size
>
> JPEG
> - 24-bit, lossy but adjustable.  File sizes often less than 1/5 of the
> uncompressed TIFF (depending on quality setting and image content)
>
> PNG
> - 24-bit, lossless.  File sizes usually a bit smaller than compressed TIFF,
> but not as small as JPEG.
> (PNG's are also readable by most browsers, which makes them useful for
> 'critical' web-display.)
>
> FWIW, I always use TIFF without compression if in any doubt (I have had
> quite a few problems with lack of portability of LZ'd TIFs), and I am now
> moving over to PNG's for my own file storage in order to save CD
> space.  The lack of 48-bit quality hasn't yet been an issue for me..
>
> mt




 




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