Surface Loading and Blitting

/*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;
const int SCREEN_HEIGHT = 480;
const int SCREEN_BPP = 32;

//The surfaces that will be used
SDL_Surface *message = NULL;
SDL_Surface *background = NULL;
SDL_Surface *screen = NULL;

SDL_Surface *load_image( std::string filename )
{
    //Temporary storage for the image that's loaded
    SDL_Surface* loadedImage = NULL;
   
    //The optimized image that will be used
    SDL_Surface* optimizedImage = NULL;
   
    //Load the image
    loadedImage = SDL_LoadBMP( filename.c_str() );
   
    //If nothing went wrong in loading the image
    if( loadedImage != NULL )
    {
        //Create an optimized image
        optimizedImage = SDL_DisplayFormat( loadedImage );
       
        //Free the old image
        SDL_FreeSurface( loadedImage );
    }
   
    //Return the optimized image
    return optimizedImage;
}

void apply_surface( int x, int y, SDL_Surface* source, SDL_Surface* destination )
{
    //Make a temporary rectangle to hold the offsets
    SDL_Rect offset;
   
    //Give the offsets to the rectangle
    offset.x = x;
    offset.y = y;
   
    //Blit the surface
    SDL_BlitSurface( source, NULL, destination, &offset );
}

int main( int argc, char* args[] )
{
    //Initialize all SDL subsystems
    if( SDL_Init( SDL_INIT_EVERYTHING ) == -1 )
    {
        return 1;   
    }
   
    //Set up the screen
    screen = SDL_SetVideoMode( SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE );
   
    //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 );
   
    //Load the images
    message = load_image( "hello_world.bmp" );
    background = load_image( "background.bmp" );
   
    //Apply the background to the screen
    apply_surface( 0, 0, background, screen );
   
    //Apply the message to the screen
    apply_surface( 180, 140, message, screen );
   
    //Update the screen
    if( SDL_Flip( screen ) == -1 )
    {
        return 1;   
    }
   
    //Wait 2 seconds
    SDL_Delay( 2000 );
   
    //Free the surfaces
    SDL_FreeSurface( message );
    SDL_FreeSurface( background );
   
    //Quit SDL
    SDL_Quit();
   
    return 0;   
}