SDL显示图片

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/*This source code copyrighted by Lazy Foo' Productions (2006) and may not be redestributed without written permission.*/
//The headers
#include "SDL/SDL.h"
#include
//The attributes of the screen
const int SCREEN_WIDTH = 640;//屏幕宽
const int SCREEN_HEIGHT = 480;//屏幕高
//const int SCREEN_BPP = 32;//色彩深度
const int SCREEN_BPP = 32;//色彩深度
//The surfaces that will be used
SDL_Surface *message = NULL;//信息表皮
SDL_Surface *background = NULL;//背景表皮
SDL_Surface *screen = NULL;//屏幕表皮

SDL_Surface *load_image( std::string filename ) //装入图片
{
    //Temporary storage for the image that's loaded
    SDL_Surface* loadedImage = NULL;  //临时存储图片
   
    //The optimized image that will be used
    SDL_Surface* optimizedImage = NULL; //最优化的表层
   
    //Load the image
    loadedImage = SDL_LoadBMP( filename.c_str() );//装载图片
   
    //If nothing went wrong in loading the image
    if( loadedImage != NULL )
    {
        //Create an optimized image
        optimizedImage = SDL_DisplayFormat( loadedImage );
      //建立一个最优化的皮肤
        //Free the old image
        SDL_FreeSurface( loadedImage );//释放
    }
    //-----------------------------------------------------------
    //Return the optimized image
    return optimizedImage;//返回最优化的
}
void apply_surface( int x, int y, SDL_Surface* source, SDL_Surface* destination )
{
    //Make a temporary rectangle to hold the offsets
    SDL_Rect offset;
    /*
  typedef struct{
     Sint16 x, y;
     Uint16 w, h;
  } SDL_Rect;
  x, y Position of the upper-left corner of the rectangle
  w, h The width and height of the rectangle
  
*/
    //Give the offsets to the rectangle
    offset.x = x;
    offset.y = y;
   
    //Blit the surface
    SDL_BlitSurface( source, NULL, destination, &offset );
/*
SDL只提供了SDL_LoadBMP()，但在SDL的示例文档中有一个用于加载图片的函数库。
SDL_BlitSurface()将图片blit进图形帧缓冲，从而显示图片。
SDL_BlitSurface()自动对blit矩形进行裁边，blit矩形在调用
SDL_UpdateRects()时被用作更新屏幕变化了的部分。
   
*/
}

int main( int argc, char* args[] )
{
    //Initialize all SDL subsystems
    if( SDL_Init( SDL_INIT_EVERYTHING ) == -1 )
    {//初使化SDL子系统
        return 1;   
    }
   
    //Set up the screen 设置屏幕
    screen = SDL_SetVideoMode( SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE );
    //屏幕宽---------高--------颜色深度
//SDL_SWSURFACE;// 请求一个软件表面.

    //If there was in error in setting up the screen
    if( screen == NULL )
    {
        return 1;   
    }
   
    //Set the window caption
    SDL_WM_SetCaption( "Hello World", NULL );//窗口标题
   
    //Load the images
    message = load_image( "hello_world.bmp" );//信息图片
    background = load_image( "background.bmp" );//背景图片
   
    //Apply the background to the screen
    apply_surface( 0, 0, background, screen );//在屏幕表皮上应用背景图片
   
    //Apply the message to the screen
    apply_surface( 180, 140, message, screen );//在屏幕表皮上应用信息图片
   
    //Update the screen
    if( SDL_Flip( screen ) == -1 )
    {
        return 1;   
    }
   
    //Wait 2 seconds
    SDL_Delay( 2000 );//延时2秒
   
    //Free the surfaces
    SDL_FreeSurface( message );//释放

    SDL_FreeSurface( background );//释放


    //Quit SDL
    SDL_Quit();
   
    return 0;   
}


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