ron@mlfarm.com (Ronald Florence) (02/10/91)
Some time ago I posted a gif -> cgi filter for SCO Xenix and Unix
systems to comp.sources.misc (volume 13). Gif-cgi is the ansi
version; gif-cgi2 is a non-ansi version. While fiddling around with
gif-cgi to look at some Magellan images, I realized that the color
mapping was fouled up, especially for use with a monochrome VGA
display. The following patch helps. Better color mapping in the SCO
Xenix monochrome VGA video driver would help even more, but that seems
to be a lost cause.
If you missed the original code, it is available from uunet or most
comp.sources.misc archives.
----------------------------[gif patch]----------------------------
*** gif.c.old Sat Feb 9 20:26:53 1991
--- gif.c Sun Feb 10 10:37:01 1991
***************
*** 19,26 ****
#include <stdio.h>
#include <signal.h>
- #define Rgb1000(c) (short)((c) * 1000.0/255.0)
-
typedef unsigned char Uchar;
short cgidev, Ystep, Xmax;
--- 19,24 ----
***************
*** 234,250 ****
Uchar *cm;
{
Uchar *scan;
int i;
short rgb[3], rgb_out[3];
for (scan = cm, i = cmap; colors > 0; scan += 3, i++, colors--)
{
! rgb[0] = Rgb1000(*scan);
! rgb[1] = Rgb1000(*(scan + 1));
! rgb[2] = Rgb1000(*(scan + 2));
! #ifdef BROKEN_MONO_VGA
! if (i > 0 && rgb[1] == 0)
! rgb[1] = 200;
#endif
vs_color(cgidev, i, rgb, rgb_out);
}
--- 232,250 ----
Uchar *cm;
{
Uchar *scan;
+ unsigned int color;
int i;
short rgb[3], rgb_out[3];
for (scan = cm, i = cmap; colors > 0; scan += 3, i++, colors--)
{
! #ifndef BROKEN_MONO_VGA
! rgb[0] = *scan << 2;
! rgb[1] = *(scan + 1) << 2;
! rgb[2] = *(scan + 2) << 2;
! #else
! color = 77 * *scan + 150 * *(scan + 1) + 29 * *(scan +2);
! rgb[0] = rgb[1] = rgb[2] = color >> 6;
#endif
vs_color(cgidev, i, rgb, rgb_out);
}
----------------------------[eof patch]----------------------------
--
Ronald Florence ron@mlfarm.com