c++ - SDL基本程序不工作但代码没问题

Question

我从 this tutorial website 下载了源 zip 文件并将内容提取到文件夹中。

然后我使用 Code::Blocks 运行教程提供的源代码(因此应该没有代码错误)但程序退出时没有显示图像或给出任何错误。

我认为问题出在 SDL_DisplayFormat(loadedImage); 上，因为它似乎返回 NULL，但使用 SDL_GetError() 我没有发现任何错误。

图片与源文件在同一目录下，是从教程网站下载的有效bmp文件。

这是源代码:

//The headers
#include "SDL/SDL.h"
#include <string>

//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 an 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.bmp" );
    background = load_image( "background.bmp" );

    //Apply the background to the screen
    apply_surface( 0, 0, background, screen );
    apply_surface( 320, 0, background, screen );
    apply_surface( 0, 240, background, screen );
    apply_surface( 320, 240, 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;
}

Answer 1

尝试将图像与可执行文件放在同一个文件夹中。因为可执行文件是要使用它们的那个，因此需要它们在同一个文件夹而不是源文件中。所以如果它在代码块中，我认为它在文件夹:“YouProjectName”/bin/Debug。 当然，您始终可以提供图像的完整路径，这样您就可以将图像放在您想要的任何文件夹中。