Manpages - SDL_SetPalette.3

SDL_SetPalette - Sets the colors in the palette of an 8-bit surface.

#include “SDL.h”

int SDL_SetPalette*(*SDL_Surface *surface, int flags, SDL_Color *colors, int firstcolor, int ncolors);

Sets a portion of the palette for the given 8-bit surface.

Palettized (8-bit) screen surfaces with the SDL_HWPALETTE flag have two palettes, a logical palette that is used for mapping blits to/from the surface and a physical palette (that determines how the hardware will map the colors to the display). SDL_BlitSurface always uses the logical palette when blitting surfaces (if it has to convert between surface pixel formats). Because of this, it is often useful to modify only one or the other palette to achieve various special color effects (e.g., screen fading, color flashes, screen dimming).

This function can modify either the logical or physical palette by specifing SDL_LOGPAL or SDL_PHYSPAL*the in the *flags parameter.

When surface is the surface associated with the current display, the display colormap will be updated with the requested colors. If SDL_HWPALETTE was set in SDL_SetVideoMode flags, SDL_SetPalette will always return 1, and the palette is guaranteed to be set the way you desire, even if the window colormap has to be warped or run under emulation.

The color components of a SDL_Color structure are 8-bits in size, giving you a total of 256^3=16777216 colors.

If surface is not a palettized surface, this function does nothing, returning 0. If all of the colors were set as passed to SDL_SetPalette, it will return 1. If not all the color entries were set exactly as given, it will return 0, and you should look at the surface palette to determine the actual color palette.

          /* Create a display surface with a grayscale palette */
          SDL_Surface *screen;
          SDL_Color colors[256];
          int i;
          .
          .
          .
          /* Fill colors with color information */
          for(i=0;i<256;i++){
            colors[i].r=i;
            colors[i].g=i;
            colors[i].b=i;
          }

          /* Create display */
          screen=SDL_SetVideoMode(640, 480, 8, SDL_HWPALETTE);
          if(!screen){
            printf("Couldn't set video mode: %s
  ", SDL_GetError());
            exit(-1);
          }

          /* Set palette */
          SDL_SetPalette(screen, SDL_LOGPAL|SDL_PHYSPAL, colors, 0, 256);
          .
          .
          .
          .

SDL_SetColors, SDL_SetVideoMode, SDL_Surface, SDL_Color