[med-svn] r2712 - trunk/packages/gdcm/trunk/debian (jpeg)

[Mathieu Malaterre]

On Wed, Nov 19, 2008 at 9:32 PM, Andreas Tille <tillea at rki.de> wrote:
> On Wed, 19 Nov 2008, malat-guest at alioth.debian.org wrote:
>
>> Modified:
>>  trunk/packages/gdcm/trunk/debian/control
>> Log:
>> BUG: remove dep to libjpeg62-dev. GDCM ships its own version of IJG
>> largely patched those two versions cannot be interchanged (libjpeg62-dev is
>> a subset of gdcm's one)
>
> Could you please be a little but more verbose about the reasons of the
> patches
> etc.  It sounds at least unusual that a widely used library as libjpeg only
> contains a subset of what you are needing.  Do you think that libjpeg inside
> Debian is broken?


Hum. I cannot find the discussion I had with Bill Allombert a while
ago. Anyway here is goes again. For most people libjpeg62 implements
the JPEG ISO/IEC IS 10918-1. Well it does not, the binary only provide
support for 8bits lossy.
While in DICOM we need:
* 8 bits lossy
* 12 bits lossy
* 8 bits lossless
* 12 bits lossless
* 16 bits lossless

So the ijg in gdcm is simply ijg (same as libjpeg62) with a well known
patch called the lossless jpeg from Ken Murchison of Oceana Matrix Ltd
(I had to patch that patch... )

For more details, see the jpeg project I maintain on sf.net:

http://gdcm.svn.sf.net/viewvc/jpeg/README?view=markup

As a side note did you know there was a libjpeg63, but that's a
complete different story :)


Anyway it should be technically possible to use libgdcmjpeg8.so.62.1.0
in place of the current libjpeg62. But keep in mind that code path
were changed to support lossless, so file that would not be supported
in the past would now be supported. I did not invest any time in
benchmarking those two libs. Anyway in short: Tom Lane (the author of
ijg) made the choice of not including the lossless patch, I cannot
possibly be the one telling the whole community they now need the
lossless patch :)

FYI, I have bcc: Tom Lane and Bill Allombert.

Take care.
-- 
Mathieu