绘制透明背景位图

// when blitting from a monochrome DC to a color DC,
// the color black in the source turns into the destination's text color,
// and the color white in the source turns into the destination's background color.
// If you blit from a color DC to a monochrome DC,
// then all pixels in the source that are equal to the background color will turn white, and all other pixels will turn black.
// In other words, GDI considers a monochrome bitmap to be black pixels on a white background.
static void DrawTransBmp( HDC hDst, HBITMAP hImg, COLORREF clrTran )
{
COLORREF colorOldFront;
COLORREF colorOldBg;

BITMAP bmp;
GetObject( hImg, sizeof( bmp ), &bmp );

HDC hForeDC = ::CreateCompatibleDC( hDst );
::SelectObject ( hForeDC, hImg );

//prepare mask dc
HDC hDCMask = CreateCompatibleDC ( hDst );
// MSDN:    When a memory device context is created, it initially has a 1-by-1 monochrome bitmap selected into it.
//          If this memory device context is used in CreateCompatibleBitmap, the bitmap that is created is a monochrome bitmap.
HBITMAP hBmpMask = CreateCompatibleBitmap( hDCMask, bmp.bmWidth, bmp.bmHeight );
::SelectObject ( hDCMask, hBmpMask );
::SetBkColor( hForeDC, clrTran );                                                //Set clrTran as blackground color
::BitBlt( hDCMask, 0, 0, bmp.bmWidth, bmp.bmHeight, hForeDC, 0, 0, SRCCOPY );    //monochrome, background color is white

//mask the foreground
::SetBkColor( hForeDC, RGB(0,0,0) );
::SetTextColor( hForeDC, RGB(255,255,255) );
::BitBlt( hForeDC, 0, 0, bmp.bmWidth, bmp.bmHeight, hDCMask, 0, 0, SRCAND );

//mask the background
colorOldBg = ::SetBkColor( hDst, RGB(255,255,255) );
colorOldFront = ::SetTextColor( hDst, RGB(0,0,0) );
::BitBlt( hDst, 0, 0, bmp.bmWidth, bmp.bmHeight, hDCMask, 0, 0, SRCAND );

//or foreground and background
::BitBlt( hDst, 0, 0, bmp.bmWidth, bmp.bmHeight, hForeDC, 0, 0, SRCPAINT );

//recover hDst color of background and foreground
::SetBkColor( hDst, colorOldBg );
::SetTextColor( hDst, colorOldFront );

//release object
::DeleteDC( hDCMask );
::DeleteDC( hForeDC );
::DeleteObject( hBmpMask );
}