Few colors in 24bpp with XFree86 on I8k
- Dear all,
I installed the nVidia drivers 1.0-1251 to my laptop (Dell Inspiron 8000
with NVidia Geforce2Go running Debian GNU/Linux 3.0) and was quite happy
to get them compiled and XFree86-4.0.3 up and running. 3D performance is
really good, but as I tried to display an image with an image viewer
(xv3.10a, Gimp 1.2.1 or Netscape 4.77) I noticed that the image looked
more like 8bpp than 24bpp! The server was definitively started with 24bpp
and 'xdpyinfo' as well as the XFree86.0.log tells me that the root window
is 24bit deep.
The test image is 8bpp depth and has 254 colors, many of them being
quite similar. The image is displayed with very few different colors:
while the image contains 254 different colors, my Geforce2Go shows me
only about 25-30 different colors! As an example, I tried to gradually
change the red component of the color <71,90,140>. The color on the
display changed every 16th iteration, so 256 different colors result in
16 different colors on the display. I assume that the display in fact
shows only 4096 different colors, which would be 12bpp.
I tried to simulate the effect in the images:
so you may have a look on how the region is displayed. The first one is
the image as it should be (in 8bpp), the second one is about what I can
see on the Geforce2Go. The problem only occurs with Linux, the display
works well with Win2k. At least, it's not a hardware problem.
I hope that somebody can give me a hint.
Dipl.-Inform. René Tschirley http://www.cs.tu-berlin.de/~pooh
TU Berlin, Computer Graphics and Computer Assisted Medicine research group