var _selectedImg = null;
function swapImg(img) 
{ 
    var imgOldSrc = null;
    
    if(img
        && img != _selectedImg //if this is the selected item, don't swap.
    ) 
    {
        imgOldSrc = img.src;
        img.src = img.lang; //swap image
        img.lang = imgOldSrc; //store swap image 
    }
}
function swapImg_click(img) 
{ 
    var former_selectedImg;

    if(img
        && _selectedImg 
        && img != _selectedImg //if this is the selected item, don't swap.
    ) 
    { //unset the former selected image.
        former_selectedImg = _selectedImg;
        _selectedImg = null;
        swapImg(former_selectedImg);
    }
    
    if(img) 
    {
        //set the new selected image.
        _selectedImg = img; //store the selected image.
    }
}