colorkeys-sdl.c

Linux游戏编程源码

/* Example of blitting with colorkeys in SDL. */

#include <SDL/SDL.h>
#include <stdio.h>
#include <stdlib.h>

int main()
{
    SDL_Surface *screen;
    SDL_Surface *background;
    SDL_Surface *image;
    SDL_Rect src, dest;
    Uint32 colorkey;

    /* Initialize SDL's video system and check for errors. */
    if (SDL_Init(SDL_INIT_VIDEO) != 0) {
	printf("Unable to initialize SDL: %s\n", SDL_GetError());
	return 1;
    }

    /* Make sure SDL_Quit gets called when the program exits! */
    atexit(SDL_Quit);

    /* Attempt to set a 640x480 hicolor (16-bit) video mode. */
    screen = SDL_SetVideoMode(640, 480, 16, 0);
    if (screen == NULL) {
	printf("Unable to set video mode: %s\n", SDL_GetError());
	return 1;
    }

    /* Load the bitmap files. */
    background = SDL_LoadBMP("background.bmp");
    if (background == NULL) {
	printf("Unable to load bitmap.\n");
	return 1;
    }

    image = SDL_LoadBMP("penguin.bmp");
    if (image == NULL) {
	printf("Unable to load bitmap.\n");
	return 1;
    }

    /* Draw the background. */
    src.x = 0;
    src.y = 0;
    src.w = background->w;
    src.h = background->h;
    dest.x = 0;
    dest.y = 0;
    dest.w = background->w;
    dest.h = background->h;
    SDL_BlitSurface(background, &src, screen, &dest);

    /* Draw the penguin without a colorkey. */
    src.x = 0;
    src.y = 0;
    src.w = image->w;
    src.h = image->h;
    dest.x = 30;
    dest.y = 90;
    dest.w = image->w;
    dest.h = image->h;
    SDL_BlitSurface(image, &src, screen, &dest);

    /* The penguin is stored on a blue background. We
       can use the SDL_MapRGB function to obtain the
       correct pixel value for pure blue. */
    colorkey = SDL_MapRGB(image->format, 0, 0, 255);

    /* We'll now enable this surface's colorkey and draw
       it again. To turn off the colorkey again, we would
       replace the SDL_SRCCOLORKEY flag with zero. */
    SDL_SetColorKey(image, SDL_SRCCOLORKEY, colorkey);
    src.x = 0;
    src.y = 0;
    src.w = image->w;
    src.h = image->h;
    dest.x = screen->w - image->w - 30;
    dest.y = 90;
    dest.w = image->w;
    dest.h = image->h;
    SDL_BlitSurface(image, &src, screen, &dest);

    /* Ask SDL to update the entire screen. */
    SDL_UpdateRect(screen, 0, 0, 0, 0);

    /* Pause for a few seconds as the viewer gasps in awe. */
    SDL_Delay(10000);

    /* Free the memory that was allocated to the bitmaps. */
    SDL_FreeSurface(background);
    SDL_FreeSurface(image);

    return 0;
}