//banner大图
var istouch = modernizr.touch,
	ismobile = false,//区分移动端与pc端
	mobile = false,//区分手机端与平板
	w_width = 0,
	w_height = 0,
	bannerimgh=638,
	navitem = 0,
	h_height=0,
	roll=0,
	stop=150,
	produs=0,
	st = 0;


function pagebox() {
    w_width = jquery(window).width();
    w_height = jquery(window).height();
}

function setimgmax(img, imgw, imgh, tw, th) {
    var twidth = tw || w_width;
    var theight = th || w_height;
    var coe = imgh / imgw;
    var coe2 = theight / twidth;
    if (coe < coe2) {
        var imgwidth = theight / coe;
        img.css({ height: theight, width: imgwidth, left: -(imgwidth - twidth) / 2, top: 0 });
    } else {
        var imgheight = twidth * coe;
        img.css({ height: imgheight, width: twidth, left: 0, top: -(imgheight - theight) / 2 });
    };
};