Vue2实现图片的拖拽,缩放和旋转效果的示例代码

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

 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;
      }
    },

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;
  }
},

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

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});
},

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);
},

/**
 * 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)`;
},

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