放大镜特效——Javascript_.b{background-color: yellow;opacity: 0.5;}-优快云博客

本文链接：https://blog.youkuaiyun.com/A_home/article/details/123934194

该博客介绍了如何使用HTML、CSS和JavaScript实现一个网页上的放大镜功能。当鼠标悬停在图片上时，会出现一个半透明的黄色遮罩，并且同步显示放大的图片细节。通过移动鼠标，可以改变放大镜的位置，查看不同区域的细节。代码中详细解释了各个部分的作用，包括事件监听和坐标计算，帮助理解放大镜效果的工作原理。

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<!DOCTYPE html>
<html lang="zh-cn">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>放大镜</title>
    <style>
      * {
        margin: 0;
        padding: 0;
        box-sizing: border-box;
      }
      .box {
        position: relative;
        top: 50px;
        left: 50px;
        width: 240px;
        height: 440px;
        background-color: #ccc;
        padding: 20px;
      }

      .box > img {
        width: 200px;
        height: 400px;
      }

      .box .mask {
        position: absolute;
        top: 0;
        left: 0;
        width: 100px;
        height: 100px;
        background-color: yellow;
        opacity: 0.5;
        display: none;
        cursor: move;
      }
      .box .big {
        position: absolute;
        top: 0;
        left: 300px;
        width: 400px;
        height: 800px;
        display: none;
        overflow: hidden;
      }

      .box .big img {
        position: absolute;
        top: 0;
        left: 0;
      }
    </style>
  </head>

  <body>
    <div class="box">
      <img src="../images/big.jpg" alt="" />
      <div class="mask"></div>
      <div class="big">
        <img src="../images/big.jpg" alt="" />
      </div>
    </div>
  </body>
  <script>
    let box = document.querySelector(".box");
    let mask = document.querySelector(".mask");
    let big = document.querySelector(".big");
    let bigImg = big.querySelector("img");

    //给盒子绑定移入移出事件
    box.addEventListener("mouseover", function () {
      mask.style.display = "block";
      big.style.display = "block";
    });
    box.addEventListener("mouseout", function () {
      mask.style.display = "none";
      big.style.display = "none";
    });

    //绑定盒子内移动事件
    box.addEventListener("mousemove", function (e) {
      //获取鼠标在盒子内的坐标
      let x = e.pageX - this.offsetLeft;
      let y = e.pageY - this.offsetTop;

      //减去遮罩层自身一半的宽高，让鼠标始终在遮罩层中央
      let maskX = x - mask.offsetWidth / 2;
      let maskY = y - mask.offsetHeight / 2;

      //遮罩层最大移动距离
      let maskMoveX = box.offsetWidth - mask.offsetWidth; 
      let maskMoveY = box.offsetHeight - mask.offsetHeight;

      //大图片最大移动距离
      let bigImgMoveX = bigImg.offsetWidth - big.offsetWidth; 
      let bigImgMoveY = bigImg.offsetHeight - big.offsetHeight;

      //限制遮罩层不超出盒子
      if (maskX <= 0) {
        maskX = 0;
      } else if (maskX >= maskMoveX) {
        maskX = maskMoveX;
      }
      if (maskY <= 0) {
        maskY = 0;
      } else if (maskY >= maskMoveY) {
        maskY = maskMoveY;
      }
      mask.style.left = maskX + "px";
      mask.style.top = maskY + "px";

      //大图片移动距离 = -（遮罩层移动距离 * 大图片最大移动距离 / 遮罩层的最大移动距离）
      bigImg.style.left = -((maskX * bigImgMoveX) / maskMoveX) + "px";
      bigImg.style.top = -((maskY * bigImgMoveY) / maskMoveY) + "px";
    });
  </script>
</html>