如何在我的窗口中加载位图？

Question

我正在尝试将位图加载到我创建的窗口中。位图应该是窗口的背景（稍后我想在其上添加标签和进度条）。

这是我的代码：

HINSTANCE hInst;
LRESULT CALLBACK WindProcedure(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam);

INT WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPSTR lpCmdLine, int nCmdShow)
{
WNDCLASSEX  WndCls;
static WCHAR szAppName[] = L"BitmapIntro";
MSG         Msg;

hInst = hInstance;
WndCls.cbSize = sizeof(WndCls);
WndCls.style = CS_OWNDC | CS_VREDRAW | CS_HREDRAW;
WndCls.lpfnWndProc = WindProcedure;
WndCls.cbClsExtra = 0;
WndCls.cbWndExtra = 0;
WndCls.hInstance = hInst;
WndCls.hIcon = LoadIcon(NULL, IDI_APPLICATION);
WndCls.hCursor = LoadCursor(NULL, IDC_ARROW);
WndCls.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
WndCls.lpszMenuName = NULL;
WndCls.lpszClassName = szAppName;
WndCls.hIconSm = LoadIcon(hInstance, IDI_APPLICATION);
RegisterClassEx(&WndCls);

CreateWindowEx(WS_EX_OVERLAPPEDWINDOW,
    szAppName,
    L"Bitmaps Fundamentals",
    WS_OVERLAPPEDWINDOW | WS_VISIBLE,
    CW_USEDEFAULT,
    CW_USEDEFAULT,
    CW_USEDEFAULT,
    CW_USEDEFAULT,
    NULL,
    NULL,
    hInstance,
    NULL);

while (GetMessage(&Msg, NULL, 0, 0))
{
    TranslateMessage(&Msg);
    DispatchMessage(&Msg);
}

return static_cast<int>(Msg.wParam);
}

LRESULT CALLBACK WindProcedure(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
HDC hDC, MemDCExercising;
PAINTSTRUCT Ps;
HBITMAP bmpExercising;

switch (Msg)
{
case WM_DESTROY:
    PostQuitMessage(WM_QUIT);
    break;
case WM_PAINT:

    hDC = BeginPaint(hWnd, &Ps);

    // Load the bitmap from the resource
    bmpExercising = LoadBitmap(hInst, MAKEINTRESOURCE(IDB_BITMAP3));
    // Create a memory device compatible with the above DC variable
    MemDCExercising = CreateCompatibleDC(hDC);
    // Select the new bitmap
    SelectObject(MemDCExercising, bmpExercising);

    // Copy the bits from the memory DC into the current dc
    BitBlt(hDC, 10, 10, 450, 400, MemDCExercising, 0, 0, SRCCOPY);

    // Restore the old bitmap
    DeleteDC(MemDCExercising);
    DeleteObject(bmpExercising);
    EndPaint(hWnd, &Ps);
    break;
default:
    return DefWindowProc(hWnd, Msg, wParam, lParam);
}
return 0;
}

问题是，PNG尺寸比窗口小，所以当PNG打开时，它只占据左高角。我怎样才能让它伸展到我的窗口大小，或者至少一遍又一遍地绘制它直到它填满窗口？

Answer 1

我怎样才能让它伸展到我的窗口大小

使用StretchBlt() 代替BitBlt()。

case WM_PAINT:
{    
    // Get the window dimensions
    RECT r;
    GetClientRect(hWnd, &r);

    // Load the bitmap from the resource
    HBITMAP bmpExercising = LoadBitmap(hInst, MAKEINTRESOURCE(IDB_BITMAP3));

    // Get the bitmap dimensions
    BITMAP bmp;
    GetObject(bmpExercising, sizeof(BITMAP), &bmp);

    PAINTSTRUCT Ps;
    HDC hDC = BeginPaint(hWnd, &Ps);

    // Create a memory device compatible with the above DC variable
    HDC MemDCExercising = CreateCompatibleDC(hDC);

    // Select the new bitmap
    HBITMAP hOldBmp = SelectObject(MemDCExercising, bmpExercising);

    // Copy the bits from the memory DC into the current dc
    StretchBlt(hDC, 0, 0, r.right - r.left, r.bottom - r.top, MemDCExercising, 0, 0, bmp.bmWidth, bmp.bmHeight, SRCCOPY);

    // Restore the old bitmap
    SelectObject(MemDCExercising, hOldBmp);

    // Destroy the memory device
    DeleteDC(MemDCExercising);

    // Destroy the bitmap
    DeleteObject(bmpExercising);

    EndPaint(hWnd, &Ps);
    break;
}

或者至少一遍又一遍地绘制它直到它填满窗口？

有两种不同的处理方式。

1. 在启动时，加载位图并使用CreatePatternBrush() 在其周围创建一个HBRUSH，然后在注册窗口类时将其分配给WNDCLASS::hbrBackground 字段。让操作系统使用位图为您绘制窗口背景。

   HBITMAP bmpExercising = LoadBitmap(hInst, MAKEINTRESOURCE(IDB_BITMAP3));
   WndCls.hbrBackground = CreatePatternBrush(bmpExercising);
   

2. 如果您想手动绘制位图，请让您的绘制处理程序在几个循环中调用BitBlt()。您知道位图的尺寸（您可以使用GetObject() 和BITMAP 结构在代码中检索），并且您知道窗口的尺寸（您可以使用GetWindowRect() 或GetClientRect() 在代码中检索） .因此，只需根据需要在不同的偏移量处多次绘制相同的位图。首先在左上角绘制一次，然后向右移动位图宽度像素并再次绘制它，重复直到移动超过窗口宽度像素。然后向左移回 0 并向下移动位图高度像素并再次重复整个宽度线，重复直到超过窗口高度像素。

   case WM_PAINT:
   {    
       // Get the window dimensions
       RECT r;
       GetClientRect(hWnd, &r);
   
       // Load the bitmap from the resource
       HBITMAP bmpExercising = LoadBitmap(hInst, MAKEINTRESOURCE(IDB_BITMAP3));
   
       // Get the bitmap dimensions
       BITMAP bmp;
       GetObject(bmpExercising, sizeof(BITMAP), &bmp);
   
       PAINTSTRUCT Ps;
       HDC hDC = BeginPaint(hWnd, &Ps);
   
       // Create a memory device compatible with the above DC variable
       HDC MemDCExercising = CreateCompatibleDC(hDC);
   
       // Select the new bitmap
       HBITMAP hOldBmp = SelectObject(MemDCExercising, bmpExercising);
   
       int width = r.right - r.left;
       int height = r.bottom - r.top;
   
       // Copy the bits from the memory DC into the current dc
       for(int y = 0; y < height; y += bmp.bmHeight)
       {
           for(int x = 0; x < width; x += bmp.bmWidth)
           {
               BitBlt(hDC, x, y, bmp.bmWidth, bmp.bmHeight, MemDCExercising, 0, 0, SRCCOPY);
           }
       }
   
       // Restore the old bitmap
       SelectObject(MemDCExercising, hOldBmp);
   
       // Destroy the memory device
       DeleteDC(MemDCExercising);
   
       // Destroy the bitmap
       DeleteObject(bmpExercising);
   
       EndPaint(hWnd, &Ps);
       break;
   }
   

现在，话虽如此，这里有一些补充说明：

1. 您不应该在您的绘图处理程序中加载位图。在创建窗口之前加载一次，然后为每个绘制操作重复使用相同的HBITMAP，直到窗口被销毁，然后释放位图。

2. LoadBitmap() 已弃用，您应该改用LoadImage()，例如：

   HBITMAP bmpExercising = (HBITMAP) LoadImage(hInst, MAKEINTRESOURCE(IDB_BITMAP3), IMAGE_BITMAP, 0, 0, LR_CREATEDIBSECTION);
   

3. 您说“位图应该是窗口的背景”，因此您应该绘制位图以响应 WM_ERASEBKGND 消息而不是 WM_PAINT 消息。

   case WM_ERASEBKGND:
   {    
       HDC hDC = (HDC) wParam;
   
       // draw the bitmap on hDC as needed...
   
       return 1;
   }