Vue實現(xiàn)剪切板圖片壓縮功能

const that = this;
  document.body.addEventListener('paste', function (event) {
    that.$fullScreenLoading.show("讀取圖片中");
    // 獲取當(dāng)前輸入框內(nèi)的文字
    const oldText = that.$refs.msgInputContainer.textContent;
    // 讀取圖片
    let items = event.clipboardData && event.clipboardData.items;
    let file = null;
    if (items && items.length) {
      // 檢索剪切板items
      for (let i = 0; i < items.length; i++) {
        if (items[i].type.indexOf('image') !== -1) {
          file = items[i].getAsFile();
          break;
        }
      }
    }
    // 預(yù)覽圖片
    const reader = new FileReader();
    reader.onload = function(event) {
      // 圖片內(nèi)容
      const imgContent = event.target.result;
      // 創(chuàng)建img標(biāo)簽
      let img = document.createElement('img');//創(chuàng)建一個img
      // 獲取當(dāng)前base64圖片信息，計算當(dāng)前圖片寬高以及壓縮比例
      let imgObj = new Image();
      let imgWidth = "";
      let imgHeight = "";
      let scale = 1;
      imgObj.src = imgContent;
      imgObj.onload = function() {
        // 計算img寬高
        if(this.width<400){
          imgWidth = this.width;
          imgHeight = this.height;
        }else{
          // 輸入框圖片顯示縮小10倍
          imgWidth = this.width/10;
          imgHeight = this.height/10;
          // 圖片寬度大于1920，圖片壓縮5倍
          if(this.width>1920){
            // 真實比例縮小5倍
            scale = 5;
          }
        }
        // 設(shè)置可編輯div中圖片寬高
        img.width = imgWidth;
        img.height = imgHeight;
        // 壓縮圖片，渲染頁面
        that.compressPic(imgContent,scale,function (newBlob,newBase) {
          // 刪除可編輯div中的圖片名稱
          that.$refs.msgInputContainer.textContent = oldText;
          img.src = newBase; //設(shè)置鏈接
          // 圖片渲染
          that.$refs.msgInputContainer.append(img);
          that.$fullScreenLoading.hide();
        });
      };
    };
    reader.readAsDataURL(file);
  });

// 參數(shù): base64地址,壓縮比例，回調(diào)函數(shù)(返回壓縮后圖片的blob和base64)
  compressPic: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");
      // 當(dāng)canvas對象的原型中沒有toBlob方法的時候，手動添加該方法
      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 > 1024*1024){
            that.compressPic(base64, scale, callback);
          }else{
            callback(blob, base64);
          }
        }, "image/jpeg");
      }
    }
  }