function prechargement()
{
    var rep = "./images/";
    var ext = ".jpg";
    var imgs = new Array( "arrplanjemwebblanc", "arrplanjemwebbleu", "arrplanjemwebjaune", "arrplanjemwebnoir", "arrplanjemwebrouge", "arrplanjemwebvert");
    for( var i = 0 ; i < imgs.length ; i++ )
    {
        var tmp = rep + imgs[ i ] + ext;
        (imgs[ i ] = new Image()).src = tmp;
    }
}