Vue2 实现图片的拖拽、缩放、旋转

本文是基于vue2 实现图片的拖拽、旋转、鼠标滚动放大缩小等功能。

效果图

分步骤实现

在这里看下 拖拽、旋转、缩放的几个方法

1.获取图片的实际宽高

getImgSize(url) {
  return new Promise((resolve, reject) => {
    let imgObj = new Image();
    imgObj.src = url;
    imgObj.onload = () => {
      resolve({
        width: imgObj.width,
        height: imgObj.height,
      });
    };
  });
},

2.根据盒子的大小、图片的大小来计算 要显示多大的图片

 async initImage() {
      if (!this.imageUrl) {
        return;
      }
      let { width, height } = await this.getImgSize(this.imageUrl);
      // 设置原始图片的大小
      let realWidth = width;
      let realHeight = height;

      // 获取高宽比例
      const whRatio = realWidth / realHeight;
      const hwRatio = realHeight / realWidth;

      //获取盒子的大小
      const boxW = this.$refs.maskBox.clientWidth;
      const boxH = this.$refs.maskBox.clientHeight;

      if (realWidth >= realHeight) {
        this.imgH = hwRatio * boxW;
        const nih = this.imgH;
        if (nih > boxH) {
          this.imgH = boxH;
          this.imgW = whRatio * boxH;
        } else {
          this.imgW = boxW;
        }
        this.top = (boxH - this.imgH) / 2;
        this.left = (boxW - this.imgW) / 2;
      } else {
        this.imgW = (boxH / realHeight) * realWidth;
        this.imgH = boxH;
        this.left = (boxW - this.imgW) / 2;
      }
    },

在这里主要是根据图片的宽高 ，以及盒子的大小来计算 盒子中展示多大的图片，将图片按照比例缩放后展示到盒子中。

3.拖拽图片

主要是监听@mousedown事件

onmousedownHandle(e) {
  const that = this;
  this.$refs.maskBox.onmousemove = function (el) {
    const ev = el || window.event; // 阻止默认事件
    ev.preventDefault();
    that.left += ev.movementX;
    that.top += ev.movementY;
  };
  this.$refs.maskBox.onmouseup = function () {
    // 鼠标抬起时将操作区域的鼠标按下和抬起事件置为null 并初始化
    that.$refs.maskBox.onmousemove = null;
    that.$refs.maskBox.onmouseup = null;
  };
  if (e.preventDefault) {
    e.preventDefault();
  } else {
    return false;
  }
},

4. 旋转图片

handleRotate() {
  this.deg += 90;
  if (this.deg >= 360) {
    this.deg = 0;
  }
  this.size = 0;
  this.scale = `scale(1) rotateZ(${this.deg}deg)`;
},

5.监听鼠标的滚动，进行缩放图片

在 mounted() 中监听鼠标的滚动事件

mounted() {
    // 兼容火狐浏览器
    this.mousewheelevt = /Firefox/i.test(navigator.userAgent)? "DOMMouseScroll" : "mousewheel";
    // 为空间区域绑定鼠标滚轮事件 =》 处理函数是wheelHandle
    // 如果你监听了window的scroll或者touchmove事件，你应该把passive设置为true，这样滚动就会流畅很多
    this.$refs.maskBox.addEventListener(this.mousewheelevt, this.wheelHandle, {passive:true});
},

处理鼠标的滚动事件

wheelHandle(e) {
    // 兼容性处理 => 火狐浏览器判断滚轮的方向是属性 detail，谷歌和ie浏览器判断滚轮滚动的方向是属性 wheelDelta
    const ev = e || window.event;
    // dir = -dir; // dir > 0 => 表示的滚轮是向上滚动，否则是向下滚动 => 范围 (-120 ~ 120)
    const dir = ev.detail ? ev.detail * -120 : ev.wheelDelta;
    //滚动的数值 / 2000 => 表示滚动的比例，用此比例作为图片缩放的比例
    this.imgScaleHandle(dir / 2000);
},

放大缩小图片

/**
 * 图片的缩放
 * zoom >0 放大
 * zoom <0 缩小
 */
imgScaleHandle(zoom) {
    this.size += zoom;
    if (this.size < -0.5) {
        this.size = -0.5;
    }
    this.scale = `scale(${1 + this.size}) rotateZ(${this.deg}deg)`;
},

页面销毁的时候 注意要取消鼠标的监听事件

beforeDestroy() {
    //取消监听
    this.$refs.maskBox.removeEventListener(this.mousewheelevt,this.wheelHandle,{passive:true});
},

以上就是主要实现功能的方法

完整代码

<template>
  <div class="home">
    <div class="btn-area">
      <button @click="switchImgHandle(1)">竖图</button>
      <button @click="switchImgHandle(2)">横图</button>
      <button @click="handleRotate">旋转</button>
      <button @click="imgScaleHandle(0.25)">放大</button>
      <button @click="imgScaleHandle(-0.25)">缩小</button>
      <button @click="handleReset">重置</button>
    </div>
    <div class="image-box" ref="maskBox" @mousedown="onmousedownHandle">
      <img :src="imageUrl" alt="" :style="{width: imgW + 'px', height: imgH + 'px',
          top: top + 'px', left: left + 'px', transform: scale, }" />
    </div>
  </div>
</template>

<script>
export default {
  name: "HomeView",
  data() {
    return {
      imageUrl: "",
      imageUrl1: require("@/assets/img1.jpg"),
      imageUrl2: require("@/assets/img2.jpg"),
      imgW: 0,
      imgW: 0,
      imgH: 0,
      deg: 0,
      top: 0,
      left: 0,
      scale: "scale(1)",
      size: 0,
      mousewheelevt: null,
    };
  },
  mounted() {
    this.imageUrl = this.imageUrl1;
    //初始化图片
    this.initImage();

    // 兼容火狐浏览器
    this.mousewheelevt = /Firefox/i.test(navigator.userAgent) ? "DOMMouseScroll" :"mousewheel";
    // 为空间区域绑定鼠标滚轮事件 =》 处理函数是wheelHandle
    // 如果你监听了window的scroll或者touchmove事件，你应该把passive设置为true，这样滚动就会流畅很多
    this.$refs.maskBox.addEventListener(this.mousewheelevt, this.wheelHandle, { passive:true});
  },
  beforeDestroy() {
    //取消监听
    this.$refs.maskBox.removeEventListener(this.mousewheelevt,this.wheelHandle,{passive:true});
  },
  methods: {
    /**
     * 切换图片
     *  flag: 1竖图 2 横图
     */
    switchImgHandle(flag) {
      if (flag === 1) {
        this.imageUrl = this.imageUrl1;
      } else {
        this.imageUrl = this.imageUrl2;
      }
      this.handleReset();
    },
    /**
     * 获取图片的url
     * @param {string} url
     */
    getImgSize(url) {
      return new Promise((resolve, reject) => {
        let imgObj = new Image();
        imgObj.src = url;
        imgObj.onload = () => {
          resolve({
            width: imgObj.width,
            height: imgObj.height,
          });
        };
      });
    },
    /**
     * 初始化图片
     */
    async initImage() {
      if (!this.imageUrl) {
        return;
      }
      let { width, height } = await this.getImgSize(this.imageUrl);
      // 设置原始图片的大小
      let realWidth = width;
      let realHeight = height;

      // 获取高宽比例
      const whRatio = realWidth / realHeight;
      const hwRatio = realHeight / realWidth;

      //获取盒子的大小
      const boxW = this.$refs.maskBox.clientWidth;
      const boxH = this.$refs.maskBox.clientHeight;

      if (realWidth >= realHeight) {
        this.imgH = hwRatio * boxW;
        const nih = this.imgH;
        if (nih > boxH) {
          this.imgH = boxH;
          this.imgW = whRatio * boxH;
        } else {
          this.imgW = boxW;
        }
        this.top = (boxH - this.imgH) / 2;
        this.left = (boxW - this.imgW) / 2;
      } else {
        this.imgW = (boxH / realHeight) * realWidth;
        this.imgH = boxH;
        this.left = (boxW - this.imgW) / 2;
      }
    },
    /**
     * 旋转
     */
    handleRotate() {
      this.deg += 90;
      if (this.deg >= 360) {
        this.deg = 0;
      }
      this.size = 0;
      this.scale = `scale(1) rotateZ(${this.deg}deg)`;
    },

    /**
     * 图片的缩放
     *    zoom >0 放大
     *    zoom <0 缩小
     */
    imgScaleHandle(zoom) {
      this.size += zoom;
      if (this.size < -0.5) {
        this.size = -0.5;
      }
      this.scale = `scale(${1 + this.size}) rotateZ(${this.deg}deg)`;
    },

    /**
     * 重置
     */
    handleReset() {
      this.imgW = 0;
      this.imgH = 0;
      this.top = 0;
      this.left = 0;
      this.deg = 0;
      this.scale = "scale(1)";
      this.size = 0;
      this.initImage();
    },

    /**
     * 鼠标滚动 实现放大缩小
     */
    wheelHandle(e) {
      const ev = e || window.event; // 兼容性处理 => 火狐浏览器判断滚轮的方向是属性 detail，谷歌和ie浏览器判断滚轮滚动的方向是属性 wheelDelta
      // dir = -dir; // dir > 0 => 表示的滚轮是向上滚动，否则是向下滚动 => 范围 (-120 ~ 120)
      const dir = ev.detail ? ev.detail * -120 : ev.wheelDelta;
      //滚动的数值 / 2000 => 表示滚动的比例，用此比例作为图片缩放的比例
      this.imgScaleHandle(dir / 2000);
    },

    /**
     * 处理图片拖动
     */
    onmousedownHandle(e) {
      const that = this;
      this.$refs.maskBox.onmousemove = function (el) {
        const ev = el || window.event; // 阻止默认事件
        ev.preventDefault();
        that.left += ev.movementX;
        that.top += ev.movementY;
      };
      this.$refs.maskBox.onmouseup = function () {
        // 鼠标抬起时将操作区域的鼠标按下和抬起事件置为null 并初始化
        that.$refs.maskBox.onmousemove = null;
        that.$refs.maskBox.onmouseup = null;
      };
      if (e.preventDefault) {
        e.preventDefault();
      } else {
        return false;
      }
    },
  },
};
</script>

<style scoped>
.home {
  width: 1000px;
  margin: 50px auto;
}
.btn-area {
  display: flex;
  justify-content: center;
  width: 100%;
  margin-bottom: 50px;
}
.btn-area button {
  width: 100px;
  height: 40px;
  font-size: 18px;
  margin-right: 10px;
}
.image-box {
  position: relative;
  margin: 0 auto;
  width: 1000px;
  height: 700px;
  border: 1px solid #333;
  overflow: hidden;
}
.image-box img {
  position: absolute;
  cursor: pointer;
}
</style>

最后附上完整的项目代码 代码仓库地址