I'm trying to write the graphics module of my engine. That is, this part of the code only provides an interface through which to load images, fonts, etc and draw them on the screen. It is also a wrapper for the library I'm using (SDL in this case).

Here are the interfaces for my Image, Font and GraphicsRenderer classes. Please tell me if I'm going the right way.

Image

class Image
{
  public:
    Image();
    Image(const Image& other);
    Image(const char* file);
    ~Image();

    bool load(const char* file);
    void free();
    bool isLoaded() const;

    Image& operator=(const Image& other);

  private:
    friend class GraphicsRenderer;
    void* data_;
};

Font

class Font
{
  public:
    Font();
    Font(const Font& other);
    Font(const char* file, int ptsize);
    ~Font();

    void load(const char* file, int ptsize);
    void free();
    bool isLoaded() const;

    Font& operator=(const Font& other);

  private:
    friend class GraphicsRenderer;
    void* data_;
};

GrapphicsRenderer

class GraphicsRenderer
{
  public:
    static GraphicsRenderer* Instance();

    void blitImage(const Image& img, int x, int y);
    void blitText(const char* string, const Font& font, int x, int y);
    void render();

  protected:
    GraphicsRenderer();
    GraphicsRenderer(const GraphicsRenderer& other);
    GraphicsRenderer& operator=(const GraphicsRenderer& other);
    ~GraphicsRenderer();

  private:
    void* screen_;

    bool initialize();
    void finalize();
};