layui图片如何放大

var ysw = 0;   //记录图片原始宽度

var ysh = 0;   //记录图片原始高度

layui.use('slider', function(){    

var $ = layui.$     

,slider = layui.slider;    

slider.render({           

elem: '#slideys'            

,value: 0 //初始值            

,theme: '#1E9FFF'           

,step: 1 //步长           

,min: -10 //最小值           

,max: 10 //最大值           

,showstep: true //开启间隔点           

,change: function(value){               

if(ysw ==0 || ysh == 0){                   

return;               

}               

var pjw = ysw/20;               

var pjh = ysh/20;               

var img =  $("#dximg");  //图片ID               

if(img!=null){                   

var w = Math.round(ysw+(pjw*value));                   

var h = Math.round(ysh+(pjh*value));                   

$(img).css("width", w );                     

$(img).css("height", h );                

}             

}         

});   

});