How To Display a Bitmap into a Rotated or Non-rectangular Area

MORE INFORMATION

Sample Code

   #define SHIFTS 15            // Extend ints to limit round-off error.
   #define THRESH (1 << SHIFTS) // Threshold for pixel size value.
				

   /* CopySourceToDest()
    *
    * Re-map a rectangular area into an area defined by four vertices.
    *
    * This function does all the real re-mapping work by recursively
    * dividing both the source and destination areas until the
    * area specified by the destination is a single pixel. At this
    * point, it copies the pixel from the source to the destination.
    *
    * By quartering both the source and the destination areas, the
    * relationship between the area in the source and the area in the
    * destination is preserved.
    *
    * NOTES:
    *   This function would be much faster if it were implemented to
    *   directly manipulate the surface bits of a DIB section rather than
    *   using GetPixel() / SetPixel().
    */ 
   void CopySourceToDest(HDC hdcDst,  POINT ul, POINT ur, POINT lr,
                         POINT ll, HDC hdcSrc,  LONG  x1, LONG  y1,
                         LONG  x2, LONG  y2)
   {
       POINT tm,lm,rm,bm,m;
       LONG mx,my;
				

       // Does the destination area specify a single pixel?
       if ((abs(ul.x - ur.x) < THRESH) &amp;&amp;
           (abs(ul.x - lr.x) < THRESH) &amp;&amp;
           (abs(ul.x - ll.x) < THRESH) &amp;&amp;
           (abs(ul.y - ur.y) < THRESH) &amp;&amp;
           (abs(ul.y - lr.y) < THRESH) &amp;&amp;
           (abs(ul.y - ll.y) < THRESH))
       {   // Yes.
           COLORREF cr;
				

   };
				

   /* WarpBlt()
    *
    * Re-map a rectangular area into an area defined by four vertices .
    *
    */ 
   void WarpBlt(HDC hdcDst,  POINT ul, POINT ur, POINT lr, POINT ll,
                HDC hdcSrc,  LONG  x1, LONG  y1, LONG  x2, LONG  y2)
   {
       // Shift all values to help reduce round-off error.
       ul.x <<= SHIFTS;
       ul.y <<= SHIFTS;
       ur.x <<= SHIFTS;
       ur.y <<= SHIFTS;
				

   }
				

   /* DemonstrateWarpBlt()
    *
    * Re-map the image of the entire screen into an area
    * defined by four random vertices .
    *
    */ 
   void DemonstrateWarpBlt(HWND hWnd)
   {
       HDC hdcScreen = GetDC(NULL);   // Source DC.
       HDC hdcWindow = GetDC(hWnd);   // Destination DC.
       POINT ul,ur,lr,ll;             // Vertices for the destination area.
       int iXRes, iYRes;              // Extents of the screen.
       RECT rc;                       // Extents of the window.
				

       // Get the size of the screen.
       iXRes = GetDeviceCaps(hdcScreen, HORZRES);
       iYRes = GetDeviceCaps(hdcScreen, VERTRES);
				

       // Get the size of our client area.
       GetClientRect(hWnd, &rc);
				

       // Define a random destination area that fits in the client area.
       ul.x = rand() % rc.right;
       ul.y = rand() % rc.bottom;
       ur.x = rand() % rc.right;
       ur.y = rand() % rc.bottom;
       lr.x = rand() % rc.right;
       lr.y = rand() % rc.bottom;
       ll.x = rand() % rc.right;
       ll.y = rand() % rc.bottom;
				

       // Copy the entire screen into the destination area.
       WarpBlt(hdcWindow, ul, ur, lr, ll,
               hdcScreen, 0, 0, iXRes, iYRes);
   }