如何使用GDI绘制半透明矩形

[cpp] view plain copy

 

/*使用GDI绘制半透明矩形*/
void CDirectXDraw::DrawHalfOpacityRect(HDC hdc,CRect rect)
{
    CDC dc;
    dc.Attach(hdc);

    CDC cdc;
    cdc.CreateCompatibleDC( &dc );

    CBitmap bitmap, *pOldBitmap;
    bitmap.CreateCompatibleBitmap( &dc, rect.right, rect.bottom );
    CRect src( rect );
    src.OffsetRect( CSize( -rect.left, -rect.top ) );
    pOldBitmap = cdc.SelectObject( &bitmap );
    cdc.FillSolidRect( src, RGB( 0, 0, 0 ) ); //透明色

    if( ::AlphaBlend == 0 )
    {
        dc.BitBlt( rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top, &cdc, src.left, src.top, SRCINVERT );

    }else{

        BLENDFUNCTION bf;
        memset( &bf, 0, sizeof( bf ) );
        bf.SourceConstantAlpha = 0x3f; //透明程度//值越大越不透明
        bf.BlendOp = AC_SRC_OVER;

        ::AlphaBlend( dc.GetSafeHdc(), rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top,
            cdc.GetSafeHdc( ), src.left, src.top, src.right - src.left, src.bottom - src.top, bf );
    }

    cdc.SelectObject( pOldBitmap );

    dc.Detach();
}

http://blog.csdn.net/lee353086/article/details/38311421