mieki256's diary

#include <windows.h>

#define SCRW 512
#define SCRH 512

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp)
{
  HDC hdc, hBmpDC;
  PAINTSTRUCT ps;
  
  static HBITMAP hBitmap, hBitmap_mask, hBitmap_bg;
  static BITMAP bp;
  static int imgw, imgh;
  static int bgw, bgh;
  static int x, y;

  switch (msg)
    {
    case WM_CREATE:
      // load bitmaps
      hBitmap = LoadBitmap(((LPCREATESTRUCT)lp)->hInstance, TEXT("BALL_IMG"));
      hBitmap_mask = LoadBitmap(((LPCREATESTRUCT)lp)->hInstance, TEXT("BALL_MSK"));
      hBitmap_bg = LoadBitmap(((LPCREATESTRUCT)lp)->hInstance, TEXT("BG_IMG"));

      // get source image information
      GetObject(hBitmap, sizeof(BITMAP), &bp);
      imgw = bp.bmWidth;
      imgh = bp.bmHeight;

      // get bg image information
      GetObject(hBitmap_bg, sizeof(BITMAP), &bp);
      bgw = bp.bmWidth;
      bgh = bp.bmHeight;

      return 0;

    case WM_PAINT:
      x = 32;
      y = 32;

      hdc = BeginPaint(hwnd, &ps);

      // draw bg image
      hBmpDC = CreateCompatibleDC(hdc);
      SelectObject(hBmpDC, hBitmap_bg);
      BitBlt(hdc, 0, 0, bgw, bgh, hBmpDC, 0, 0, SRCCOPY);
      DeleteDC(hBmpDC);

      // draw mask
      hBmpDC = CreateCompatibleDC(hdc);
      SelectObject(hBmpDC, hBitmap_mask);
      BitBlt(hdc, x, y, imgw, imgh, hBmpDC, 0, 0, SRCAND);
      DeleteDC(hBmpDC);

      // draw source image
      hBmpDC = CreateCompatibleDC(hdc);
      SelectObject(hBmpDC, hBitmap);
      BitBlt(hdc, x, y, imgw, imgh, hBmpDC, 0, 0, SRCPAINT);
      DeleteDC(hBmpDC);

      EndPaint(hwnd, &ps);
      return 0;

    case WM_DESTROY:
      DeleteObject(hBitmap);
      DeleteObject(hBitmap_mask);
      DeleteObject(hBitmap_bg);
      PostQuitMessage(0);
      return 0;
    }

  return DefWindowProc(hwnd, msg, wp, lp);
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                   PSTR lpCmdLine, int nCmdShow)
{
  HWND hwnd;
  MSG msg;
  WNDCLASS winc;

  winc.style            = CS_HREDRAW | CS_VREDRAW;
  winc.lpfnWndProc      = WndProc;
  winc.cbClsExtra       = winc.cbWndExtra   = 0;
  winc.hInstance        = hInstance;
  winc.hIcon            = LoadIcon(NULL, IDI_APPLICATION);
  winc.hCursor          = LoadCursor(NULL, IDC_ARROW);
  winc.hbrBackground    = (HBRUSH)GetStockObject(WHITE_BRUSH);
  winc.lpszMenuName     = NULL;
  winc.lpszClassName    = TEXT("DrawBitmapSample");

  if (!RegisterClass(&winc)) return -1;

  hwnd = CreateWindow(
    TEXT("DrawBitmapSample"), TEXT("Draw Bitmap Sample"),
    WS_OVERLAPPEDWINDOW | WS_VISIBLE,
    CW_USEDEFAULT, CW_USEDEFAULT,
    SCRW, SCRH,
    NULL, NULL,
    hInstance, NULL
    );

  if (hwnd == NULL) return -1;

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

  return msg.wParam;
}

BALL_IMG BITMAP "test.bmp"
BALL_MSK BITMAP "test_mask.bmp"
BG_IMG BITMAP "bg.bmp"

• bg.bmp。背景にする画像。
• test.bmp。元ソース画像。抜け部分にしたいところは黒(#000000)にしておく。
• test_mask.bmp。マスク画像。不透明部分は黒(#000000)、透明部分は白(#ffffff)にしておく。アルファチャンネルを白黒反転させた状態とも言える。

01_draw_bitmap.exe: 01_draw_bitmap.o bmp_res.o
        gcc 01_draw_bitmap.o bmp_res.o -o 01_draw_bitmap.exe -mwindows

01_draw_bitmap.o: 01_draw_bitmap.c
        gcc -c 01_draw_bitmap.c

bmp_res.o: bmp_res.rc test.bmp test_mask.bmp bg.bmp
        windres bmp_res.rc bmp_res.o

.PHONY: clean
clean:
        rm -f *.exe
        rm -f *.o

• マスク画像を AND (SRCAND) で重ねることで、マスク画像の黒い部分は黒く、白い部分は描画先の元の色が残る状態になる。
• 本来描きたかったソース画像を OR (SRCPAINT) で重ねることで、ぼっかり黒く抜けた部分にソース画像がハメ込まれるような状態になる。