[filmscanners] RE: JPEG2000 > Paul

["Robert Meier" <filmscanner@meierlim.com>]

>-----Original Message-----
>From: filmscanners_owner@halftone.co.uk
>I curios to know, How can we to verify that compression is loss-less?

For 24-bit compress it, decompress it, subtract the decompressed file from
the original file and then either look at the histogram or change the
levels. Note that if you just look at the resulting image then you will have
a hard time to see small errors. For more then 16-bits you have to use some
other utility to subtract one image from the other.

>Loss less compression suggests that J2K can be used for archiving also.
>Am I right here?

Yes, j2k can compress LOSSLESS. There might be some implementation that say
it's lossless although it isn't. But in that case it's a problem of the
implementation and not a problem of j2k.

>Few extra seconds for compression is not a problem for me, as long
>as I can reduce
>my CD bulk.

Tiff also allows lzw which is quite fast but not as effective as j2k,
though. Note that with j2k you only get a compression ratio of approx 1:2
for lossless compression.

Robert

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