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Few colors in 24bpp with XFree86 on I8k

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  • Rene Tschirley
    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
    Message 1 of 1 , Aug 27, 2001
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      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:

      http://www.cs.tu-berlin.de/~pooh/snap-good.gif
      http://www.cs.tu-berlin.de/~pooh/snap-bad.gif

      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.


      Bye,
      René

      --
      Dipl.-Inform. René Tschirley http://www.cs.tu-berlin.de/~pooh
      TU Berlin, Computer Graphics and Computer Assisted Medicine research group
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