js实现图片局部放大效果详解

for(var i = 0;i

content.Onmousemove= function (e) {
    var evt = window.event||e;

    larger.style.display = "block";
    shadow.style.display = "block";
    var clientX = evt.clientX;
    var clientY = evt.clientY;

    var scrollLeft = document.documentElement.scrollLeft||document.body.scrollLeft;
    var scrollTop = document.documentElement.scrollTop||document.body.scrollTop;

    var X = clientX+scrollLeft-chooseMarginL-shadowW/2;
    var Y = clientY+scrollTop-chooseMarginT-shadowH/2;

    if(X<=0){
      X = 0;
    }
    if(X>=maxX){
      X = maxX;
    }
    if(Y<=0){
      Y = 0;
    }
    if(Y>=maxY){
      Y = maxY;
    }
//    防止遮罩层粘滞，跟随鼠标一起滑出大图位置
    var bigX = X*bigW/contentW;
    var bigY = Y*bigH/contentH;
// bigX / bigW = X / contentW,主图和遮罩层之间存在两倍关系，放大图和原图之间也有两倍关系
    shadow.style.left = X+"px";
    shadow.style.top = Y+"px";

    big.style.left = -bigX+"px";
    big.style.top = -bigY+"px";

  }