半透明效果

HBITMAP bg,girl;
HDC mdc;

const int xstart=50;
const int ystart=20;

HWND hWnd;

   hInst = hInstance; // 将实例句柄存储在全局变量中
   HDC hdc,bufdc;
   HBITMAP bmp;

   hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
      CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL);

   if (!hWnd)
   {
      return FALSE;
   }

   ShowWindow(hWnd, nCmdShow);
   UpdateWindow(hWnd);
 
   hdc =GetDC(hWnd);
   mdc=CreateCompatibleDC(hdc);
   bufdc=CreateCompatibleDC(hdc);
   girl=CreateCompatibleBitmap(hdc,298,329);

   BITMAP bm1,bm2;
   unsigned char *px1,*px2;

   //处理背景图
   bg=(HBITMAP)LoadImage(NULL,"sky2.bmp",IMAGE_BITMAP,600,450,LR_LOADFROMFILE);
   bmp=(HBITMAP)LoadImage(NULL,"dra.bmp",IMAGE_BITMAP,298,329,LR_LOADFROMFILE);
   GetObject(bg,sizeof(BITMAP),&bm1);
  
   if (bm1.bmBitsPixel!=32&&bm1.bmBitsPixel!=24)
   {
    MessageBox(NULL,"此程序只能在32bit或24bit显示模式中运行","警告",0);
    return FALSE;
   }

   SelectObject(mdc,girl);
   SelectObject(bufdc,bg);
   BitBlt(mdc,0,0,298,329,bufdc,xstart,ystart,SRCCOPY);
   SelectObject(bufdc,bmp);
   BitBlt(mdc,0,0,298,329,bufdc,298,0,SRCAND);
   BitBlt(mdc,0,0,298,329,bufdc,0,0,SRCPAINT);
   px1=new unsigned char[bm1.bmHeight*bm1.bmWidthBytes];
   GetBitmapBits(bg,bm1.bmHeight*bm1.bmWidthBytes,px1);

   //处理前景图
  
   GetObject(girl,sizeof(BITMAP),&bm2);
   px2=new unsigned char[bm2.bmHeight*bm2.bmWidthBytes];
   GetBitmapBits(girl,bm2.bmHeight*bm2.bmWidthBytes,px2);

   int xend,yend;
   int x,y,i;
   int rgb_b;
   int PxBytes=bm1.bmBitsPixel/8;

   xend=xstart+298;
   yend=ystart+329;

   //处理背景图像像素颜色
   for (y=ystart;y<yend;y++)
   {
    for (x=xstart;x<xend;x++)
    {
     rgb_b=y*bm1.bmWidthBytes+x*PxBytes;

     px1[rgb_b]=px1[rgb_b]*0.7;
     px1[rgb_b+1]=px1[rgb_b+1]*0.7;
     px1[rgb_b+2]=px1[rgb_b+2]*0.7;
    }
   }//836588

   //处理前景图像素颜色
   for (y=0;y<(bm2.bmHeight);y++)
   {
    for (x=0;x<bm2.bmWidth;x++)
    {
     rgb_b=y*bm2.bmWidthBytes+x*PxBytes;
     i=(ystart+y)*bm1.bmWidthBytes+(xstart+x)*PxBytes;

     px2[rgb_b]=px2[rgb_b]*0.3+px1[i];
     px2[rgb_b+1]=px2[rgb_b+1]*0.3+px1[i+1];
     px2[rgb_b+2]=px2[rgb_b+2]*0.3+px1[i+2];
    }
   }

   SetBitmapBits(girl,bm2.bmHeight*bm2.bmWidthBytes,px2);

   //贴上背景图
   SelectObject(mdc,bg);
   BitBlt(hdc,0,0,600,450,mdc,0,0,SRCCOPY);
   //贴上处理后的半透明图
   SelectObject(mdc,girl);
   BitBlt(hdc,xstart,ystart,298,329,mdc,0,0,SRCCOPY);
  
   ReleaseDC(hWnd,hdc);
   delete [] px1;
   delete [] px2;
 
   return TRUE;