libopenjpeg Problem

[Mark]

The current development version of mtPaint has successfully used
libopenjpeg version 1.1.1 to read and write RGB/RGBA images from/to
JPEG 2000 files on both Windows and Linux systems.

While testing the code we discovered a small problem which occurs when
saving 32 bit RGBA files (8 bits per channel) on Linux systems. The
problem occurs when saving an image with a rate of 1 or more (i.e.
tcp_rate[0]=1, 2, 3, etc), whereby all alpha pixels are stored as
value 128. I have uploaded the archive called jp2_alpha.zip into the
files section which contains an example. The PNG file is the original
and the other files are saved in Windows or Linux at rate 10.

Just to clarify, saving RGBA images in Windows always works perfectly
(whatever the rate), and saving RGBA images at rate 0 in Linux also
works perfectly (only rates 1 or more cause the problem).

Can anyone think of a possible cause for this strange problem?

Thanks,
Mark.