透過色を指定して画像をコピーする

この下の背景に

このカップを重ねます。

TransparentBlt関数を使用して、

白を透過色としてコピーします。

すると、

このように背景とカップが重なります。

 

〇プログラム例

 

  1. #pragma comment(lib,"msimg32.lib")
  2.  
  3. #include <windows.h>
  4.  
  5. static LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
  6. {
  7.     HDC hdc;
  8.     PAINTSTRUCT ps;
  9.     POINT pt;
  10.     LPSTR str = TEXT("こんにちは、日本");
  11.     static HDC hMemDC;
  12.     static HBITMAP hBitmap, hBackBmp;
  13.     static HFONT hFont[2];
  14.     LPSTR BitMapFile = TEXT("カップ.bmp");
  15.     LPSTR Back_BitMapFile = TEXT("背景.bmp");
  16.  
  17.     static BITMAP bitmap, bitmapBack;
  18.  
  19.     switch (uMsg)
  20.     {
  21.     case WM_DESTROY:
  22.         DeleteDC(hMemDC);
  23.         DeleteObject(hBitmap);
  24.         DeleteObject(hBackBmp);
  25.         DeleteObject(hFont[0]);
  26.  
  27.         PostQuitMessage(0);
  28.         return 0;
  29.  
  30.     case WM_CREATE:
  31.         hFont[0] = CreateFont(
  32.             40, 0, 0, 0,
  33.             FW_NORMAL, FALSE, FALSE, FALSE,
  34.             SHIFTJIS_CHARSET, OUT_DEFAULT_PRECIS,
  35.             CLIP_DEFAULT_PRECIS, DEFAULT_QUALITY,
  36.             VARIABLE_PITCH | FF_DONTCARE, L"メイリオ"
  37.         );
  38.         ShowWindow(hWnd, SW_SHOW);
  39.         hMemDC = CreateCompatibleDC(NULL);
  40.         hBitmap = LoadImage(NULL, BitMapFile, IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
  41.         hBackBmp = LoadImage(NULL, Back_BitMapFile, IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
  42.  
  43.         GetObject(hBitmap, sizeof(BITMAP), &bitmap);
  44.         GetObject(hBackBmp, sizeof(BITMAP), &bitmapBack);
  45.  
  46.         return 0;
  47.  
  48.     case WM_PAINT:
  49.         hdc = BeginPaint(hWnd, &ps);
  50.         //背景の描画
  51.         SelectObject(hMemDC, hBackBmp);
  52.         BitBlt(hdc, 0, 0, bitmapBack.bmWidth, bitmapBack.bmHeight, hMemDC, 0, 0, SRCCOPY);
  53.  
  54.         pt.x = bitmapBack.bmWidth / 2 - bitmap.bmWidth / 2;
  55.         pt.y = bitmapBack.bmHeight - bitmap.bmHeight;
  56.  
  57.         //カップの描画
  58.         SelectObject(hMemDC, hBitmap);
  59.         TransparentBlt(hdc, pt.x, pt.y, bitmap.bmWidth, bitmap.bmHeight,
  60.             hMemDC, 0, 0, bitmap.bmWidth, bitmap.bmHeight, RGB(255,255,255));
  61.  
  62.         SelectObject(hdc, hFont[0]);
  63.         SetTextColor(hdc, RGB(0, 0xFF, 0));
  64.         TextOut(hdc, 0, 0, str, lstrlen(str));
  65.         EndPaint(hWnd, &ps);
  66.  
  67.         return 0;
  68.     }
  69.  
  70.     return DefWindowProc(hWnd, uMsg, wParam, lParam);
  71.  
  72. }
  73.  
  74. int APIENTRY wWinMain(
  75.     _In_ HINSTANCE hInstance,
  76.     _In_opt_ HINSTANCE hPrevInstance,
  77.     _In_ LPWSTR ipCmdLine,
  78.     _In_ int nCmdShow
  79. ) {
  80.  
  81.     WNDCLASSEXW wcex;
  82.  
  83.     wcex.cbSize = sizeof(WNDCLASSEX);
  84.  
  85.     wcex.style = CS_HREDRAW | CS_VREDRAW;
  86.     wcex.lpfnWndProc = WndProc;
  87.     wcex.cbClsExtra = 0;
  88.     wcex.cbWndExtra = 0;
  89.     wcex.hInstance = hInstance;
  90.     wcex.hIcon = NULL;
  91.     wcex.hCursor = NULL;
  92.     wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
  93.     wcex.lpszMenuName = NULL;
  94.     wcex.lpszClassName = TEXT("TestWindow");
  95.     wcex.hIconSm = NULL;
  96.  
  97.     RegisterClassExW(&wcex);
  98.  
  99.     HWND hWnd = CreateWindowEx(0UL, TEXT("TestWindow"), TEXT("日本"), WS_OVERLAPPEDWINDOW,
  100.         CW_USEDEFAULT, 0, 400, 400, NULL, NULL, hInstance, NULL);
  101.  
  102.     if (!hWnd)
  103.     {
  104.         return FALSE;
  105.     }
  106.  
  107.     MSG msg;
  108.  
  109.     while (GetMessage(&msg, NULL, 0, 0))
  110.     {
  111.         DispatchMessage(&msg);
  112.     }
  113.  
  114.     return (int)msg.wParam;
  115. }