Re: [Jpeg-users] setting up lossless jpeg

[Mathieu M. <mat...@gm...>]

Hi Jim,

On Mon, Dec 1, 2008 at 11:05 PM, Jim Moody
<bb...@us...> wrote:
> Hello, I have been using the IJG library for a few years,
> but now need lossless decompression for some DICOM data I
> received. I saw your comments on fixunix.com regarding JPEG
> Lossless decompression, and I'm a bit confused on what to
> download from source forge. The thread mentions that a
> "famous patch" is available from the sourceforge jpeg
> project site, but is it a separate item or is has it already
> been applied to some version (6c perhaps?)?  Can you point
> me to the specific package or packages I need to download in
> order to have a library that support lossless jpeg
> (de)compression?

In short:
You need the following patch: ljpeg-patch.v6b.tar.gz  (ftp.oceana.com
section in sf.net download). This file was downloaded from official
oceana ftp site at a time where it was still available.

OR you can download a prepatch version + cmake as:
ljpeg-62.1.0.tar.bz2   (section ljpeg in sf.net download).

libjpeg6c is a release prepared by Guido which has some upcoming
features, but does not include the lossless patch.

As a side note there are still a couple of place where the lossless
patch is not working, so I would suggest you have a look at what is
being done in GDCM or DCMTK. ref:

http://apps.sourceforge.net/mediawiki/gdcm/index.php?title=GDCM_Release_2.0

I need to merge local gdcm patch back into the jpeg sf.net release.


> Is there some document that explains the differences between
> the various packages you have here? (what is the difference
> between what oceana.com has and jpegclub, and ijg.org?)

Not that I know of.
IJG: official 6b version (lossy only)
jpegclub: 6c version from guido (lossy only)
oceana: 6b + lossless patch (lossy+lossless).

If you are to process lossless jpeg, do not forget to compile the
12bits/16bits version of IJG. See what is being done in the cmake
version to avoid duplicating source code.

2cts
-- 
Mathieu