Vue实现剪切板图片压缩功能

const that = this;
  document.body.addEventListener('paste', function (event) {
    that.$fullScreenLoading.show("读取图片中");
    // 获取当前输入框内的文字
    const oldText = that.$refs.msgInputContainer.textContent;
    // 读取图片
    let items = event.clipboardData && event.clipboardData.items;
    let file = null;
    if (items && items.length) {
      // 检索剪切板items
      for (let i = 0; i < items.length; i++) {
        if (items[i].type.indexOf('image') !== -1) {
          file = items[i].getAsFile();
          break;
        }
      }
    }
    // 预览图片
    const reader = new FileReader();
    reader.onload = function(event) {
      // 图片内容
      const imgContent = event.target.result;
      // 创建img标签
      let img = document.createElement('img');//创建一个img
      // 获取当前base64图片信息，计算当前图片宽高以及压缩比例
      let imgObj = new Image();
      let imgWidth = "";
      let imgHeight = "";
      let scale = 1;
      imgObj.src = imgContent;
      imgObj.onload = function() {
        // 计算img宽高
        if(this.width<400){
          imgWidth = this.width;
          imgHeight = this.height;
        }else{
          // 输入框图片显示缩小10倍
          imgWidth = this.width/10;
          imgHeight = this.height/10;
          // 图片宽度大于1920，图片压缩5倍
          if(this.width>1920){
            // 真实比例缩小5倍
            scale = 5;
          }
        }
        // 设置可编辑div中图片宽高
        img.width = imgWidth;
        img.height = imgHeight;
        // 压缩图片，渲染页面
        that.pressPic(imgContent,scale,function (newBlob,newBase) {
          // 删除可编辑div中的图片名称
          that.$refs.msgInputContainer.textContent = oldText;
          img.src = newBase; //设置链接
          // 图片渲染
          that.$refs.msgInputContainer.append(img);
          that.$fullScreenLoading.hide();
        });
      };
    };
    reader.readAsDataURL(file);
  });

// 参数: base64地址,压缩比例，回调函数(返回压缩后图片的blob和base64)
  pressPic:function(base64, scale, callback){
    const that = this;
    let _img = new Image();
    _img.src = base64;
    _img.onload = function() {
      let _canvas = document.createElement("canvas");
      let w = this.width / scale;
      let h = this.height / scale;
      _canvas.setAttribute("width", w);
      _canvas.setAttribute("height", h);
      _canvas.getContext("2d").drawImage(this, 0, 0, w, h);
      let base64 = _canvas.toDataURL("image/jpeg");
      // 当canvas对象的原型中没有toBlob方法的时候，手动添加该方法
      if (!HTMLCanvasElement.prototype.toBlob) {
        Object.defineProperty(HTMLCanvasElement.prototype, 'toBlob', {
          value: function (callback, type, quality) {
            let binStr = atob(this.toDataURL(type, quality).split(',')[1]),
              len = binStr.length,
              arr = new Uint8Array(len);
            for (let i = 0; i < len; i++) {
              arr[i] = binStr.charCodeAt(i);
            }
            callback(new Blob([arr], {type: type || 'image/png'}));
          }
        });
      }else{
        _canvas.toBlob(function(blob) {
          if(blob.size > 10241024){
            that.pressPic(base64, scale, callback);
          }else{
            callback(blob, base64);
          }
        }, "image/jpeg");
      }
    }
  }