放大镜效果-优快云博客

本文链接：https://blog.youkuaiyun.com/weixin_49582736/article/details/112648441
<!DOCTYPE html>
<html>

<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <!--<link rel="stylesheet" href="css/index.css">-->
    <style>
        img {
            display: block;
        }

        * {
            margin: 0;
            padding: 0;
        }

        .box {
            width: 350px;
            height: 350px;
            margin: 100px;
            position: relative;
        }

        .big {
            width: 400px;
            height: 400px;
            position: absolute;
            top: 0;
            left: 360px;
            overflow: hidden;
            display: none;
        }

        .big img {
            position: absolute;
        }

        .mask {
            width: 100px;
            height: 100px;
            background: rgba(255, 255, 0, 0.4);
            position: absolute;
            top: 0px;
            left: 0px;
            cursor: move;
            display: none;
        }

        .small {
            position: relative;
        }
    </style>
</head>

<body>
    <div class="box" id="box">
        <div class="small" id="small">
            <img src="图片地址" width="350" alt="" />
            <div class="mask" id="mask"></div>
        </div>
        <div class="big" id="big">
            <img src="图片地址" width="800" alt="" id="img" />
        </div>
    </div>
</body>


<script>
    //1  获取节点
    var boxObj = document.querySelector('#box');
    var smallObj = document.getElementById('small');
    var imgsmall = smallObj.firstElementChild;
    var mackObj = smallObj.lastElementChild;
    var bigObj = document.getElementById('big');
    var imgbig = bigObj.firstElementChild;

    console.log(mackObj);
    // 2 给small绑定鼠标移入事件
    smallObj.onmouseenter = function () {
        // 2-1 显示mask和大图
        mackObj.style.display = 'block';
        bigObj.style.display = 'block';
    }

    // 3 鼠标移出消失
    smallObj.onmouseleave = () => {
        mackObj.style.display = 'none';
        bigObj.style.display = 'none';
    }

    //4 鼠标移动则让mask跟随
    smallObj.onmousemove = (eve) => {
        var e = eve || window.event;
        // 4-1 获取鼠标的实时位置
        let wSx = e.pageX;
        let wSy = e.pageY;
        // console.log(wSx);
        // console.log(wSy);

        // 4-2 获取box的left和top值,计算出鼠标相对于small的坐标
        let boxLeft = boxObj.offsetLeft;
        let boxTop = boxObj.offsetTop;
        // console.log(boxLeft);
        // console.log(boxTop);

        var maskX = wSx - boxLeft - mackObj.offsetWidth / 2;
        var maskY = wSy - boxTop - mackObj.offsetHeight / 2;



        // 4-3 边界的设置
        // 上面的边界
        if (maskX < 0) {
            maskX = 0;
        }
        if (maskY < 0) {
            maskY = 0;
        }
        var smallObjWx = smallObj.offsetWidth - mackObj.offsetWidth;
        var smallObjHx = smallObj.offsetHeight - mackObj.offsetHeight;

        if (maskX > smallObjWx) {
            maskX = smallObjWx;
        }
        if (maskY > smallObjHx) {
            maskY = smallObjHx;
        }

        // 给mask设置位置
        mackObj.style.top = maskY + 'px';
        mackObj.style.left = maskX + 'px';

        //黄色盒子覆盖到哪里,对应的大盒子里图片展示哪里
        //  mask移动的距离 / mask移动的最大距离 == img移动的距离 / img移动的最大距离
        //img移动的距离 = mask移动的距离 / mask移动的最大距离 * img移动的最大距离
        let smeentX = imgbig.offsetWidth - bigObj.offsetWidth;
        let smeentY = imgbig.offsetHeight - bigObj.offsetHeight;

        // 由公式算出 大图的left和top
        let lenterX = maskX / smallObjWx * smeentX;
        let lenterY = maskY / smallObjHx * smeentY;

        // 设置给大图
        imgbig.style.top = -lenterY + 'px';
        imgbig.style.left = -lenterX + 'px';
        console.log(lenterX);
    }

</script>   

</html>