c++ - 如何从 bmp 图像 C++ 纹理中获取 Sprite 集

Question

我有这张图片:

我想生成一组 sprite，每个大小为 32x32。我怎么能用 C++ 做到这一点，没有使用任何库。纹理类:

class Texture
{

protected:
    // We cannot create or copy base class texture objects
    // We will only ever have pointers or references to base
    // class texture objects used in our program (and these
    // will refer to derived class textures
    Texture() = default;
    Texture(Texture const &) = default;
    Texture & operator=(Texture const &) = default;

    virtual void LoadFromFile(std::string const & strFileName) = 0;
    virtual void LoadFromResource(unsigned int rid) = 0;

public:
    virtual ~Texture(){}

    //  virtual Rect const & GetBounds() const = 0;
    virtual int Width() const = 0;
    virtual int Height() const = 0;
};

using TEXTURE_PTR = std::shared_ptr<Texture>;

Sprite 类:

class Sprite
{
private:

    virtual void draw_impl(Canvas & c) = 0;
    TEXTURE_PTR  m_pTexture;

protected:
    // Ensure that Sprite objects can only be constructed by derived classes
    explicit Sprite(TEXTURE_PTR pt = nullptr,POINT2f const & p = { 0, 0 });

    // All Sprite objects have a position state variable
    POINT2f  m_position;


    // Sprite objects can only be copied by derived class objects
    Sprite(const Sprite&) = default;
    Sprite& operator=(const Sprite&) = default;

public:

    virtual ~Sprite(){}

    void OnDraw(Canvas & c);

    void SetPosition(POINT2f const & pos);
    POINT2f const & GetPosition() const;
    void SetTexture(TEXTURE_PTR pt);

};

然后我以这种方式创建 Sprite :

TEXTURE_PTR pLightning = std::make_shared<Texture>("resource//Lightning.bmp", RGB(255, 0, 255));
std::shared_ptr<Sprite> pSpark = std::make_shared<Sprite>(pLightning);

如何使用这种方法从上图中生成 9 个 Sprite ？

编辑我想出了这些代码，但仍然不起作用

class WinTexture : public Texture
{

protected:
    HBITMAP m_hbmImage;
    HBITMAP m_hbmMask;
    BITMAP  m_bmParam;


    virtual void LoadFromResource(UINT rid);
    virtual void LoadFromFile(std::string const & strFileName);
    void CreateMask(DWORD dwTransparent);

public:
    // Construct from Windows Resource
    WinTexture(UINT uid, COLORREF dwTransparent);

    // Constructor from file load
    WinTexture(std::string const & strFilename, COLORREF dwTransparent);

    //Contruct from other Texture
    WinTexture(std::shared_ptr<WinTexture> wt, int xStart,int yStart, int w, int h);

    virtual ~WinTexture();

    // Inherited interface
//  virtual Rect const & GetBounds() const;
    virtual int Width() const;
    virtual int Height() const;

    HBITMAP ImageHandle() const;
    HBITMAP MaskHandle() const;

};

有了这个，我想创建一个从其他 WinTexture 创建的构造函数:

WinTexture::WinTexture(std::shared_ptr<WinTexture> wt, int xStart, int yStart, int w, int h)
    : Texture(),                // as above
    m_hbmImage(NULL),
    m_hbmMask(NULL) {
    HDC hdcMem1 = CreateCompatibleDC(0);
    HDC hdcMem2 = CreateCompatibleDC(0);

    m_hbmImage = CreateBitmap(w, h, 1, 1, NULL);
    //m_hbmImage = CreateCompatibleBitmap(hdcMem2, 1, 1);
    SelectObject(hdcMem1, wt->ImageHandle());
    SelectObject(hdcMem2, m_hbmImage);
    BitBlt(hdcMem2, xStart, yStart, w, h,hdcMem1, 0, 0, SRCCOPY);
    BitBlt(hdcMem1, xStart, yStart, w, h, hdcMem2, 0, 0, SRCINVERT);
    //SaveDC(hdcMem2);
    DeleteDC(hdcMem1);
    DeleteDC(hdcMem2);
    CreateMask(RGB(0, 0, 0));
}

编辑目前，我已经从 Sprite 创建了这个类:

class TexturedSprite : public Sprite
{
    private:
        TEXTURE_PTR  m_pTexture;

        virtual void draw_impl(Canvas & c);

    protected:

    public:
        explicit TexturedSprite(TEXTURE_PTR pt = nullptr, POINT2f pos = { 32, 32});
        explicit TexturedSprite(int xStart,int yStart, int w, int h,TEXTURE_PTR pt = nullptr, POINT2f pos = { 32, 32 });

        virtual ~TexturedSprite(){}

        void SetTexture(TEXTURE_PTR pt);
};

我不知道如何实现第二个构造函数，复制输入纹理的一部分(pt):

TexturedSprite::TexturedSprite(int xStart, int yStart, int w, int h, TEXTURE_PTR pt , POINT2f pos )
:Sprite(pos)
{
    HDC hdcMem1 = CreateCompatibleDC(0);
    HDC hdcMem2 = CreateCompatibleDC(0);
//How to assign values to DC?
    BitBlt(hdcMem1, 32, 32, w, h, hdcMem2, xStart, yStart, SRCCOPY);
    DeleteDC(hdcMem1);
    DeleteDC(hdcMem2);
}

Answer 1

至少在我现在阅读内容时，您的基本意图是加载纹理，然后通过将 32x32 像素的纹理片段复制到单个 Sprite 中来创建单个 Sprite 。除非您打算从单独的线程中操纵 Sprite (我觉得这不太可能)，否则我会避免这样做。

相反，我会记下您提供给 BitBlt 的最后几个参数:

BitBlt(hdcMem2, xStart, yStart, w, h,hdcMem1, 0, 0, SRCCOPY);

SRCCOPY 之前的 0, 0 指定源位图中用作 BitBlt 起点的位置。

这样您就可以加载一次纹理，并且只需将单个纹理用于​​它包含的所有 Sprite 。在特定位置绘制单个 Sprite 只需要您在源位图中指定该 Sprite 的 X、Y 坐标(特别是该 Sprite 的左上角)并从那里开始绘制一个 32x32 的 block 。如果你想定义单独的 Sprite 对象，你当然可以这样做，但每个只需要存储一些东西，比如 shared_ptr 到加载的纹理，以及它的纹理的 X，Y 坐标。

class Sprite {
    shared_ptr<Texture> tex;
    int x, y;
public:
    Sprite(shared_ptr<Texture> t, int x, int y) tex(t), x(x), y(y) {}

    void draw(HDC dc, int dest_x, int dest_y) { 
        BitBlt(dc, dest_x, dest_y, 32, 32, *tex, x, y, SRCCOPY);
    }
};