SDL_Surface *surface;
SDL_PixelFormat *fmt;
SDL_Color *color;
Uint8 index;

.
.

/* Create surface */
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fmt=surface->format;

/* Check the bitdepth of the surface */
if(fmt->BitsPerPixel!=8){
  fprintf(stderr, "Not an 8-bit surface.\n");
  return(-1);
}

/* Lock the surface */
SDL_LockSurface(surface);

/* Get the topleft pixel */
index=*(Uint8 *)surface->pixels;
color=fmt->palette->colors[index];

/* Unlock the surface */
SDL_UnlockSurface(surface);
printf("Pixel Color-> Red: %d, Green: %d, Blue: %d. Index: %d\n",
          color->r, color->g, color->b, index);
.
.

/* Extracting color components from a 32-bit color value */
SDL_PixelFormat *fmt;
SDL_Surface *surface;
Uint32 temp, pixel;
Uint8 red, green, blue, alpha;
.
.
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fmt = surface->format;
SDL_LockSurface(surface);
pixel = *((Uint32*)surface->pixels);
SDL_UnlockSurface(surface);

/* Get Red component */
temp = pixel & fmt->Rmask;  /* Isolate red component */
temp = temp >> fmt->Rshift; /* Shift it down to 8-bit */
temp = temp << fmt->Rloss;  /* Expand to a full 8-bit number */
red = (Uint8)temp;

/* Get Green component */
temp = pixel & fmt->Gmask;  /* Isolate green component */
temp = temp >> fmt->Gshift; /* Shift it down to 8-bit */
temp = temp << fmt->Gloss;  /* Expand to a full 8-bit number */
green = (Uint8)temp;

/* Get Blue component */
temp = pixel & fmt->Bmask;  /* Isolate blue component */
temp = temp >> fmt->Bshift; /* Shift it down to 8-bit */
temp = temp << fmt->Bloss;  /* Expand to a full 8-bit number */
blue = (Uint8)temp;

/* Get Alpha component */
temp = pixel & fmt->Amask;  /* Isolate alpha component */
temp = temp >> fmt->Ashift; /* Shift it down to 8-bit */
temp = temp << fmt->Aloss;  /* Expand to a full 8-bit number */
alpha = (Uint8)temp;

printf("Pixel Color -> R: %d,  G: %d,  B: %d,  A: %d\n", red, green, blue, alpha);
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