setrgbpalette

Syntax

#include <graphics.h>
void setrgbpalette(int colornum, int red, int green, int blue);

Description

setrgbpalette can be used with the IBM 8514 and VGA drivers.

colornum defines the palette entry to be loaded, while red, green, and blue define the component colors of the palette entry.

For the IBM 8514 display (and the VGA in 256K color mode), colornum is in the range 0 to 255. For the remaining modes of the VGA, colornum is in the range 0 to 15. Only the lower byte of red, green, or blue is used, and out of each byte, only the 6 most significant bits are loaded in the palette.

For compatibility with other IBM graphics adapters, the BGI driver defines the first 16 palette entries of the IBM 8514 to the default colors of the EGA/VGA. These values can be used as is, or they can be changed using setrgbpalette.

Return Value

None.

Windows Notes

The winbgim version allows the the colornum to be a palette index from 0 to 15. The call

    setrgbpalette(colornum, r, g, b);

is similar to

    setpalette(colornum, COLOR(r,g,b) );

The difference is that setrgbpalette will use only the six most significant bits of the least significant byte of r, g and b. However, COLOR(r,g,b) uses the entire least significant byte of r, g and b. color argument to be an ordinary BGI color (from 0 to 15) or an RGB color.

In the windows version, changing the palette effects only future drawing. Currently drawn pixels do not change their color when the palette changes (no "palette animation").

See also

setpalette

Example

/* setrgbpalette example */ 

#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>

int main(void)
{
   /* select driver and mode that supports use of setrgbpalette */
   int gdriver = VGA, gmode = VGAHI, errorcode;
   struct palettetype pal;
   int i, ht, y, xmax;

   /* initialize graphics and local variables */
   initgraph(&gdriver, &gmode, "");

   /* read result of initialization */
   errorcode = graphresult();
   if (errorcode != grOk) {  /* an error occurred */

      printf("Graphics error: %s\n", grapherrormsg(errorcode));
      printf("Press any key to halt:");
      getch();
      exit(1);               /* terminate with an error code */
   }

   /* grab a copy of the palette */
   getpalette(&pal);


   /* create gray scale */
   for (i=0; i<pal.size; i++)
      setrgbpalette(pal.colors[i], i*4, i*4, i*4);

   /* display the gray scale */
   ht = getmaxy() / 16;
   xmax = getmaxx();
   y = 0;
   for (i=0; i<pal.size; i++) {

      setfillstyle(SOLID_FILL, i);
      bar(0, y, xmax, y+ht);
      y += ht;
   }

   /* clean up */
   getch();
   closegraph();
   return 0;
}