I am coding in c++, gdi I use stretchDIBits to draw Images to dc.

        ::SetStretchBltMode(hDC, HALFTONE);
    	::StretchDIBits(
    		hDC,
    		des.left,des.top,des.right - des.left,des.bottom - des.top,
    		0, 0,
    		img.getWidth(),
    		img.getHeight(),
    		(img.accessPixels()), 
    		(img.getInfo()),
    		DIB_RGB_COLORS,
    		SRCCOPY
    		);

However It is slow. So I changed to use DrawDib function.

::SetStretchBltMode(hDC, HALFTONE);
DrawDibDraw(
            			hdd,
            			hDC,
            			des.left,des.top,des.right - des.left,des.bottom - des.top,
            			(LPBITMAPINFOHEADER)(img.getInfo()),
            			(img.accessPixels()), 
            			0, 0,
            			img.getWidth(),
            			img.getHeight(),
            			DDF_HALFTONE
            			);

However the result is just like draw by COLORONCOLOR Mode. How can I improve the drawing quality?