html5 图片缩放 鼠标滚轮 鼠标滚轮实现图片的放大缩小

滚轮控制元素放大缩小

#img{ position: absolute; top: 100px; left: 200px; }

var img = document.querySelector("#img");

mouseWheel(img, function (event,down){

var oldWidth = this.offsetWidth; //宽高初始值

var oldHeight = this.offsetHeight;

var oldLeft = this.offsetLeft; //偏移量初始值

var oldTop = this.offsetTop;

var x = event.clientX; //鼠标坐标

var y = event.clientY;

//鼠标坐标的位置在图片中的比例

var scaleX = (x - oldLeft) / oldWidth;

var scaleY = (y - oldTop) / oldHeight;

//(鼠标坐标 - 元素初始偏移量 = 鼠标坐标在元素体内的距离)/ 元素初始宽高

if(down){

this.width = oldWidth + 10; //滚轮向下滚宽度+10

if (this.width > 800){

this.width = 800;

}

}else{

this.width = oldWidth - 10; //滚轮向上滚宽度-10

if (this.width < 300){

this.width = 300;

}

}

//获取图片大小的变化量

var imgChangeWidth = this.offsetWidth - oldWidth;

var imgChangeHeight = this.offsetHeight - oldHeight;

//鼠标在图片中的比例 * 图片大小的变化量 = left/top的变化量

var l = oldLeft - (scaleX * imgChangeWidth);

var t = oldTop - (scaleY * imgChangeHeight);

this.style.left = l + "px";

this.style.top = t + "px";

});