nanogui: Images resolution
Subject:
Re: Images resolution
From:
"Greg Haerr" ####@####.####
Date:
20 Jan 2000 17:21:56 -0000
Message-Id: <01aa01bf6369$5ad6b680$15320cd0@gregh>
: Is there anything I can do, to improve the resolution of an
: image. ? I am using the "bios VGA" driver, and the image of
: the "car" on the microwindows demo sucks big time. I guess
: that must be some color/resolution thing that is not been
: configured correctly.
I'm not sure if your problem is pixel resolution or color resolution.
The car will look fine at 640x480, but you've got to be running
a 256 color palette mode, or a truecolor mode that supports
at least about 250 colors, or the car's image will degrade.
As I think about it, you're probably running RTEMS Microwindows,
which uses the hardware scr_bios.c driver. This driver _doesn't_
implement the setpalette() driver function, but instead runs in
the VGA default 16 color mode. So all your colors are ugly.
The reason this works at all is that your driver returns ncolors=16,
and the first 16 colors of the 256 color palette basically match
the std VGA colors, so the Microwindows color-reduction
algorithm basically maps image colors to the right values.
The fix is somewhat hard: the std VGA runs in max 640x480x16
colors, without special programming. The extended programming
depends on the chipset. We may need grab some libraries
like GRX or SVGA and write special chipset-specific drivers
to get the 256 color modes. What we really need is the GRX
package ported to RTEMS or DOS.
Regards,
Greg
