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#include <stdio.h>
#include <SDL/SDL.h>
#include <emscripten.h>
static const int COLOR_COUNT = 32;
static SDL_Surface *screen;
static SDL_Color pal[COLOR_COUNT +1];
void initializePalette() {
//initialize sdl palette
//with red green and blue
//colors
pal[0].r = 0;
pal[0].g = 0;
pal[0].b = 0;
pal[0].unused = 0;
for (int i=1; i< 1 + COLOR_COUNT; i++) {
pal[i].r = 255 / COLOR_COUNT * i;
pal[i].g = 0;
pal[i].b = 0;
pal[i].unused = 0;
}
SDL_SetColors(screen, pal, 0, 1 + COLOR_COUNT);
}
void animatePalette() {
SDL_Color temporary;
temporary = pal[1];
for (int i=2; i< 1 + COLOR_COUNT; i++) {
pal[i-1] = pal[i];
}
pal[COLOR_COUNT] = temporary;
SDL_SetColors(screen, pal, 1, COLOR_COUNT);
//refreshing
SDL_LockSurface(screen);
SDL_UnlockSurface(screen);
printf("yet another cycle\n");
}
int main() {
SDL_Init(SDL_INIT_VIDEO);
screen = SDL_SetVideoMode(600, 400, 8, SDL_HWSURFACE | SDL_HWPALETTE);
//test empty pallete
SDL_LockSurface(screen);
SDL_UnlockSurface(screen);
initializePalette();
//palette is red yellow blue
SDL_LockSurface(screen);
int size = screen->h * screen->pitch;
char *color = screen->pixels;
int divider = size / COLOR_COUNT;
int i = 0;
while (i < size) {
*color = 1 + (i / divider); //red
color++;
i++;
}
SDL_UnlockSurface(screen);
//Animation
printf("you should see red gradient animation\n");
emscripten_set_main_loop(animatePalette, 0, 1);
SDL_Quit();
return 0;
}
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