Draw bitmap with grayed 3D effect

//
//      DitherBlt :     Draw a bitmap dithered (3D grayed effect like disabled buttons in toolbars) into a destination DC
//      Author :        Jean-Edouard Lachand-Robert (iamwired@geocities.com), June 1997.
//
//      hdcDest :       destination DC
//      nXDest :        x coordinate of the upper left corner of the destination rectangle into the DC
//      nYDest :        y coordinate of the upper left corner of the destination rectangle into the DC
//      nWidth :        width of the destination rectangle into the DC
//      nHeight :       height of the destination rectangle into the DC
//      hbm :           the bitmap to draw (as a part or as a whole)
//      nXSrc :         x coordinates of the upper left corner of the source rectangle into the bitmap
//      nYSrc :         y coordinates of the upper left corner of the source rectangle into the bitmap
//
void DitherBlt (HDC hdcDest, int nXDest, int nYDest, int nWidth, 
				int nHeight, HBITMAP hbm, int nXSrc, int nYSrc)
{
	ASSERT(hdcDest && hbm);
	ASSERT(nWidth > 0 && nHeight > 0);
	
	// Create a generic DC for all BitBlts
	HDC hDC = CreateCompatibleDC(hdcDest);
	ASSERT(hDC);
	
	if (hDC)
	{
		// Create a DC for the monochrome DIB section
		HDC bwDC = CreateCompatibleDC(hDC);
		ASSERT(bwDC);
		
		if (bwDC)
		{
			// Create the monochrome DIB section with a black and white palette
			struct {
				BITMAPINFOHEADER bmiHeader; 
				RGBQUAD 		 bmiColors[2]; 
			} RGBBWBITMAPINFO = {
				
				{		// a BITMAPINFOHEADER
					sizeof(BITMAPINFOHEADER),	// biSize 
						nWidth, 				// biWidth; 
						nHeight,				// biHeight; 
						1,						// biPlanes; 
						1,						// biBitCount 
						BI_RGB, 				// biCompression; 
						0,						// biSizeImage; 
						0,						// biXPelsPerMeter; 
						0,						// biYPelsPerMeter; 
						0,						// biClrUsed; 
						0						// biClrImportant; 
				},
				
				{
					{ 0x00, 0x00, 0x00, 0x00 }, { 0xFF, 0xFF, 0xFF, 0x00 }
					} 
			};
			VOID *pbitsBW;
			HBITMAP hbmBW = CreateDIBSection(bwDC,
				(LPBITMAPINFO)&RGBBWBITMAPINFO, DIB_RGB_COLORS, &pbitsBW, NULL, 0);
			ASSERT(hbmBW);
			
			if (hbmBW)
			{
				// Attach the monochrome DIB section and the bitmap to the DCs
				SelectObject(bwDC, hbmBW);
				SelectObject(hDC, hbm);
				
				// BitBlt the bitmap into the monochrome DIB section
				BitBlt(bwDC, 0, 0, nWidth, nHeight, hDC, nXSrc, nYSrc, SRCCOPY);
				
				// Paint the destination rectangle in gray
				FillRect(hdcDest, CRect(nXDest, nYDest, nXDest + nWidth, nYDest +
					nHeight), GetSysColorBrush(COLOR_3DFACE));
				
				// BitBlt the black bits in the monochrome bitmap into COLOR_3DHILIGHT bits in the destination DC
				// The magic ROP comes from the Charles Petzold's book
				HBRUSH hb = CreateSolidBrush(GetSysColor(COLOR_3DHILIGHT));
				HBRUSH oldBrush = (HBRUSH)SelectObject(hdcDest, hb);
				BitBlt(hdcDest, nXDest + 1, nYDest + 1, nWidth, nHeight, bwDC, 0, 0, 0xB8074A);
				
				// BitBlt the black bits in the monochrome bitmap into COLOR_3DSHADOW bits in the destination DC
				hb = CreateSolidBrush(GetSysColor(COLOR_3DSHADOW));
				DeleteObject(SelectObject(hdcDest, hb));
				BitBlt(hdcDest, nXDest, nYDest, nWidth, nHeight, bwDC, 0, 0, 0xB8074A);
				DeleteObject(SelectObject(hdcDest, oldBrush));
			}
			
			VERIFY(DeleteDC(bwDC));
		}
		
		VERIFY(DeleteDC(hDC));
	}
}