SDL_image's IMG_Load do not work

Question

I am using IMG_Load() to load png file, but it simply not working. loadedImage = IMG_Load(filename.c_str()); after this sentence, loadedImage is still NULL,not error happened. PS:I am using VS C++2008, png file is in the develop folder. Here is my code:(It is exactly what Lazy Foo like)

//The headers

include "SDL.h"

include "SDL_image.h"

include

pragma comment( linker, "/subsystem:\"windows\" /entry:\"mainCRTStartup\"" )

//Screen attributes const int SCREEN_WIDTH = 640; const int SCREEN_HEIGHT = 480; const int SCREEN_BPP = 32;

//The surfaces SDL_Surface *image = NULL; SDL_Surface *screen = NULL;

SDL_Surface *load_image( std::string filename ) { //The image that's loaded SDL_Surface* loadedImage = NULL;

//The optimized image that will be used
SDL_Surface* optimizedImage = NULL;

//Load the image using SDL_image

loadedImage = IMG_Load(filename.c_str());

//If the image loaded
if( loadedImage != NULL )
{
    //Create an optimized image

//cout<<"Flag"; 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 ) { //Rectangle to hold the offsets SDL_Rect offset;

//Get offsets
offset.x = x;
offset.y = y;

//Blit the surface
SDL_BlitSurface( source, NULL, destination, &offset );

}

bool init() { //Initialize all SDL subsystems if( SDL_Init( SDL_INIT_EVERYTHING ) == -1 ) { return false; }

//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 false;
}

//Set the window caption
SDL_WM_SetCaption( "PNG test", NULL );

//If everything initialized fine
return true;

}

void clean_up() { //Free the surface SDL_FreeSurface( image );

//Quit SDL
SDL_Quit();

}

int main( int argc, char* args[] ) { //Initialize if( init() == false ) { return 1; }

//Load the image
image = load_image( "look.png" );

//If there was a problem in loading the image
if( image == NULL )
{
    return 5;
}

//Apply the surface to the screen
apply_surface( 0, 0, image, screen );

//Update the screen
if( SDL_Flip( screen ) == -1 )
{
    return 1;
}

//Wait 2 seconds
SDL_Delay( 2000 );

//Free the surface and quit SDL
clean_up();


return 0;

}

The output return 5.

Answer 1

my bad. I just copy SDL_image.dll to exe floder. I should also copy zlib1.dll and libpng12-0.dll Actually, all the dll is need, because if there is not such dll, the program won't give any error prompt, which is confusing.