<canvas canvas-id='attendCanvasId' class='myCanvas'></canvas>

// 點擊加_壓縮 takePhoto: function () {  var that = this;  let imgViewList = that.data.imgViewList; //這個是用來承載頁面循環展示圖片的   //拍照、從相冊選擇上傳   wx.chooseImage({    count: 4,  //這個是上傳的最大數量，默認為9    sizeType: ['compressed'],  //這個可以理解為上傳的圖片質量類型（官方給的），雖然沒什么卵用，要不然還要我們自己寫壓縮做什么    sourceType: ['album', 'camera'],  //這個是圖片來源，相冊或者相機    success: function (res) {     var tempFilePaths = res.tempFilePaths  //這個是選擇后返回的圖片列表     that.getCanvasImg(0, 0, tempFilePaths);  //進行壓縮    }    }); }, //壓縮并獲取圖片，這里用了遞歸的方法來解決canvas的draw方法延時的問題 getCanvasImg: function (index,failNum, tempFilePaths){  var that = this;  if (index < tempFilePaths.length){   const ctx = wx.createCanvasContext('attendCanvasId');   ctx.drawImage(tempFilePaths[index], 0, 0, 300, 150);   ctx.draw(true, function () {    index = index + 1;//上傳成功的數量，上傳成功則加1    wx.canvasToTempFilePath({     canvasId: 'attendCanvasId',     success: function success(res) {      that.uploadCanvasImg(res.tempFilePath);      that.getCanvasImg(index,failNum,tempFilePaths);     }, fail: function (e) {      failNum += 1;//失敗數量，可以用來提示用戶      that.getCanvasImg(inedx,failNum,tempFilePaths);     }    });   });  } }, //上傳圖片 uploadCanvasImg: function (canvasImg){  var that = this;  let imgViewList = that.data.imgViewList;  var tempImg = canvasImg;  wx.uploadFile({   url: app.d.fileServer,//文件服務器的地址   filePath: tempImg,   formData: {    paramPath: "gift"   },   name: 'file',   success: function (res) {    var json2map = JSON.parse(res.data);    imgViewList.push(app.d.imageUrlFix + json2map[0].fileUrl);    that.setData({     imgViewList: imgViewList,    })   }  }) },