在make文件中链接SDL_image

Question

我的Makefile -

all:
    g++ main.cpp -I/usr/local/include -L/usr/local/lib -lSDL2 -lSDL_image

我使用的代码来自教程 -

/*This source code copyrighted by Lazy Foo' Productions (2004-2013) */

//Using SDL, SDL_image, standard IO, and strings
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
#include <stdio.h>
#include <string>

//Screen dimension constants
const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;

//Texture wrapper class
class LTexture
{
    public:
        //Initializes variables
        LTexture();

        //Deallocates memory
        ~LTexture();

        //Loads image at specified path
        bool loadFromFile( std::string path );

        #ifdef _SDL_TTF_H
        //Creates image from font string
        bool loadFromRenderedText( std::string textureText, SDL_Color textColor );
        #endif

        //Deallocates texture
        void free();

        //Set color modulation
        void setColor( Uint8 red, Uint8 green, Uint8 blue );

        //Set blending
        void setBlendMode( SDL_BlendMode blending );

        //Set alpha modulation
        void setAlpha( Uint8 alpha );

        //Renders texture at given point
        void render( int x, int y, SDL_Rect* clip = NULL, double angle = 0.0, SDL_Point* center = NULL, SDL_RendererFlip flip = SDL_FLIP_NONE );

        //Gets image dimensions
        int getWidth();
        int getHeight();

    private:
        //The actual hardware texture
        SDL_Texture* mTexture;

        //Image dimensions
        int mWidth;
        int mHeight;
};

//The application time based timer
class LTimer
{
    public:
        //Initializes variables
        LTimer();

        //The various clock actions
        void start();
        void stop();
        void pause();
        void unpause();

        //Gets the timer's time
        Uint32 getTicks();

        //Checks the status of the timer
        bool isStarted();
        bool isPaused();

    private:
        //The clock time when the timer started
        Uint32 mStartTicks;

        //The ticks stored when the timer was paused
        Uint32 mPausedTicks;

        //The timer status
        bool mPaused;
        bool mStarted;
};

//The dot that will move around on the screen
class Dot
{
    public:
        //The dimensions of the dot
        static const int DOT_WIDTH = 20;
        static const int DOT_HEIGHT = 20;

        //Maximum axis velocity of the dot
        static const int DOT_VEL = 10;

        //Initializes the variables
        Dot();

        //Takes key presses and adjusts the dot's velocity
        void handleEvent( SDL_Event& e );

        //Moves the dot
        void move();

        //Shows the dot on the screen
        void render();

    private:
        //The X and Y offsets of the dot
        int mPosX, mPosY;

        //The velocity of the dot
        int mVelX, mVelY;
};

//Starts up SDL and creates window
bool init();

//Loads media
bool loadMedia();

//Frees media and shuts down SDL
void close();

//The window we'll be rendering to
SDL_Window* gWindow = NULL;

//The window renderer
SDL_Renderer* gRenderer = NULL;

//Scene textures
LTexture gDotTexture;

LTexture::LTexture()
{
    //Initialize
    mTexture = NULL;
    mWidth = 0;
    mHeight = 0;
}

LTexture::~LTexture()
{
    //Deallocate
    free();
}

bool LTexture::loadFromFile( std::string path )
{
    //Get rid of preexisting texture
    free();

    //The final texture
    SDL_Texture* newTexture = NULL;

    //Load image at specified path
    SDL_Surface* loadedSurface = IMG_Load( path.c_str() );
    if( loadedSurface == NULL )
    {
        printf( "Unable to load image %s! SDL_image Error: %s\n", path.c_str(), IMG_GetError() );
    }
    else
    {
        //Color key image
        SDL_SetColorKey( loadedSurface, SDL_TRUE, SDL_MapRGB( loadedSurface->format, 0, 0xFF, 0xFF ) );

        //Create texture from surface pixels
        newTexture = SDL_CreateTextureFromSurface( gRenderer, loadedSurface );
        if( newTexture == NULL )
        {
            printf( "Unable to create texture from %s! SDL Error: %s\n", path.c_str(), SDL_GetError() );
        }
        else
        {
            //Get image dimensions
            mWidth = loadedSurface->w;
            mHeight = loadedSurface->h;
        }

        //Get rid of old loaded surface
        SDL_FreeSurface( loadedSurface );
    }

    //Return success
    mTexture = newTexture;
    return mTexture != NULL;
}

#ifdef _SDL_TTF_H
bool LTexture::loadFromRenderedText( std::string textureText, SDL_Color textColor )
{
    //Get rid of preexisting texture
    free();

    //Render text surface
    SDL_Surface* textSurface = TTF_RenderText_Solid( gFont, textureText.c_str(), textColor );
    if( textSurface != NULL )
    {
        //Create texture from surface pixels
        mTexture = SDL_CreateTextureFromSurface( gRenderer, textSurface );
        if( mTexture == NULL )
        {
            printf( "Unable to create texture from rendered text! SDL Error: %s\n", SDL_GetError() );
        }
        else
        {
            //Get image dimensions
            mWidth = textSurface->w;
            mHeight = textSurface->h;
        }

        //Get rid of old surface
        SDL_FreeSurface( textSurface );
    }
    else
    {
        printf( "Unable to render text surface! SDL_ttf Error: %s\n", TTF_GetError() );
    }


    //Return success
    return mTexture != NULL;
}
#endif

void LTexture::free()
{
    //Free texture if it exists
    if( mTexture != NULL )
    {
        SDL_DestroyTexture( mTexture );
        mTexture = NULL;
        mWidth = 0;
        mHeight = 0;
    }
}

void LTexture::setColor( Uint8 red, Uint8 green, Uint8 blue )
{
    //Modulate texture rgb
    SDL_SetTextureColorMod( mTexture, red, green, blue );
}

void LTexture::setBlendMode( SDL_BlendMode blending )
{
    //Set blending function
    SDL_SetTextureBlendMode( mTexture, blending );
}

void LTexture::setAlpha( Uint8 alpha )
{
    //Modulate texture alpha
    SDL_SetTextureAlphaMod( mTexture, alpha );
}

void LTexture::render( int x, int y, SDL_Rect* clip, double angle, SDL_Point* center, SDL_RendererFlip flip )
{
    //Set rendering space and render to screen
    SDL_Rect renderQuad = { x, y, mWidth, mHeight };

    //Set clip rendering dimensions
    if( clip != NULL )
    {
        renderQuad.w = clip->w;
        renderQuad.h = clip->h;
    }

    //Render to screen
    SDL_RenderCopyEx( gRenderer, mTexture, clip, &renderQuad, angle, center, flip );
}

int LTexture::getWidth()
{
    return mWidth;
}

int LTexture::getHeight()
{
    return mHeight;
}


Dot::Dot()
{
    //Initialize the offsets
    mPosX = 0;
    mPosY = 0;

    //Initialize the velocity
    mVelX = 0;
    mVelY = 0;
}

void Dot::handleEvent( SDL_Event& e )
{
    //If a key was pressed
    if( e.type == SDL_KEYDOWN && e.key.repeat == 0 )
    {
        //Adjust the velocity
        switch( e.key.keysym.sym )
        {
            case SDLK_UP: mVelY -= DOT_VEL; break;
            case SDLK_DOWN: mVelY += DOT_VEL; break;
            case SDLK_LEFT: mVelX -= DOT_VEL; break;
            case SDLK_RIGHT: mVelX += DOT_VEL; break;
        }
    }
    //If a key was released
    else if( e.type == SDL_KEYUP && e.key.repeat == 0 )
    {
        //Adjust the velocity
        switch( e.key.keysym.sym )
        {
            case SDLK_UP: mVelY += DOT_VEL; break;
            case SDLK_DOWN: mVelY -= DOT_VEL; break;
            case SDLK_LEFT: mVelX += DOT_VEL; break;
            case SDLK_RIGHT: mVelX -= DOT_VEL; break;
        }
    }
}

void Dot::move()
{
    //Move the dot left or right
    mPosX += mVelX;

    //If the dot went too far to the left or right
    if( ( mPosX < 0 ) || ( mPosX + DOT_WIDTH > SCREEN_WIDTH ) )
    {
        //Move back
        mPosX -= mVelX;
    }

    //Move the dot up or down
    mPosY += mVelY;

    //If the dot went too far up or down
    if( ( mPosY < 0 ) || ( mPosY + DOT_HEIGHT > SCREEN_HEIGHT ) )
    {
        //Move back
        mPosY -= mVelY;
    }
}

void Dot::render()
{
    //Show the dot
    gDotTexture.render( mPosX, mPosY );
}

bool init()
{
    //Initialization flag
    bool success = true;

    //Initialize SDL
    if( SDL_Init( SDL_INIT_VIDEO ) < 0 )
    {
        printf( "SDL could not initialize! SDL Error: %s\n", SDL_GetError() );
        success = false;
    }
    else
    {
        //Enable VSync
        if( !SDL_SetHint( SDL_HINT_RENDER_VSYNC, "1" ) )
        {
            printf( "Warning: VSync not enabled!" );
        }

        //Set texture filtering to linear
        if( !SDL_SetHint( SDL_HINT_RENDER_SCALE_QUALITY, "1" ) )
        {
            printf( "Warning: Linear texture filtering not enabled!" );
        }

        //Create window
        gWindow = SDL_CreateWindow( "SDL Tutorial", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN );
        if( gWindow == NULL )
        {
            printf( "Window could not be created! SDL Error: %s\n", SDL_GetError() );
            success = false;
        }
        else
        {
            //Create renderer for window
            gRenderer = SDL_CreateRenderer( gWindow, -1, SDL_RENDERER_ACCELERATED );
            if( gRenderer == NULL )
            {
                printf( "Renderer could not be created! SDL Error: %s\n", SDL_GetError() );
                success = false;
            }
            else
            {
                //Initialize renderer color
                SDL_SetRenderDrawColor( gRenderer, 0xFF, 0xFF, 0xFF, 0xFF );

                //Initialize PNG loading
                int imgFlags = IMG_INIT_PNG;
                if( !( IMG_Init( imgFlags ) & imgFlags ) )
                {
                    printf( "SDL_image could not initialize! SDL_image Error: %s\n", IMG_GetError() );
                    success = false;
                }
            }
        }
    }

    return success;
}

bool loadMedia()
{
    //Loading success flag
    bool success = true;

    //Load dot texture
    if( !gDotTexture.loadFromFile( "26_motion/dot.bmp" ) )
    {
        printf( "Failed to load dot texture!\n" );
        success = false;
    }

    return success;
}

void close()
{
    //Free loaded images
    gDotTexture.free();

    //Destroy window    
    SDL_DestroyRenderer( gRenderer );
    SDL_DestroyWindow( gWindow );
    gWindow = NULL;
    gRenderer = NULL;

    //Quit SDL subsystems
    IMG_Quit();
    SDL_Quit();
}

int main( int argc, char* args[] )
{
    //Start up SDL and create window
    if( !init() )
    {
        printf( "Failed to initialize!\n" );
    }
    else
    {
        //Load media
        if( !loadMedia() )
        {
            printf( "Failed to load media!\n" );
        }
        else
        {   
            //Main loop flag
            bool quit = false;

            //Event handler
            SDL_Event e;

            //The dot that will be moving around on the screen
            Dot dot;

            //While application is running
            while( !quit )
            {
                //Handle events on queue
                while( SDL_PollEvent( &e ) != 0 )
                {
                    //User requests quit
                    if( e.type == SDL_QUIT )
                    {
                        quit = true;
                    }

                    //Handle input for the dot
                    dot.handleEvent( e );
                }

                //Move the dot
                dot.move();

                //Clear screen
                SDL_SetRenderDrawColor( gRenderer, 0xFF, 0xFF, 0xFF, 0xFF );
                SDL_RenderClear( gRenderer );

                //Render objects
                dot.render();

                //Update screen
                SDL_RenderPresent( gRenderer );
            }
        }
    }

    //Free resources and close SDL
    close();

    return 0;
}

我的错误 -

g++ main.cpp -I/usr/local/include -L/usr/local/lib -lSDL2 -lSDL_image.lib
ld: library not found for -lSDL_image.lib
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [all] Error 1

我无法加载此内容。我使用brew安装SDL2_image，它似乎存在于usr / local / lib等。我看到了libSDL_image.a和其他各种各样的东西。

有人可以告诉我如何编辑mac的makefile，以便我可以编译我试图使用的代码。我不知道为什么-lSDL_image不能正常工作。

Answer 1

要加载SDL_image，它应该是

-lSDL_image

但你没有使用SDL 1.X你正在使用SDL 2，所以它应该是

-lSDL2_image

如果它仍然说无法找到它，那么你需要确保它位于ld搜索的路径中。

-L/Path/To/SDL_image

如果仍然无效，请确保您拥有开发库，而不仅仅是运行时二进制文件

您可以在此处获取SDL_image的开发库：http://www.libsdl.org/projects/SDL_image/