Page({ /** * 頁面的初始數據 */ data: { imgUrl: "項目中圖片地址", //圖片鏈接 img: '' // 合成后圖片路徑 }, /** * 生命周期函數--監聽頁面加載 */ onLoad: function (options) { let that = this; wx.downloadFile({  url: '線上圖片地址',  success(res) {  // 繪制背景海報到canvas  var postersize = that.setCanvasSize(750);//動態設置畫布大小  const ctx = wx.createCanvasContext('shareCanvas')  ctx.drawImage(that.data.imgUrl, 0, 0, postersize.w, postersize.h)  var re = wx.getSystemInfoSync();  var scale = 750 / 180;  var width = re.windowWidth / scale;  var height = width  var leftscale = 750 / 480; // 180為left  var left = re.windowWidth / leftscale;  var topscale = 750 / 880; // 180為top  var top = re.windowWidth / topscale;  ctx.drawImage(res.tempFilePath, left, top, width, height)  ctx.draw()  setTimeout(() => {   // code_url = this.canvasToTempImage();    //獲取臨時緩存合成照片路徑，存入data中   wx.canvasToTempFilePath({   canvasId: 'shareCanvas',   success: function (res) {    var tempFilePath = res.tempFilePath;    that.setData({    img: tempFilePath    })    console.log(tempFilePath)   },   fail: function (res) {    console.log(res);   }   });  }, 1000);  } })  }, /** * 生命周期函數--監聽頁面初次渲染完成 */ onReady: function () {  }, /** * 生命周期函數--監聽頁面顯示 */ onShow: function () {  }, /** * 生命周期函數--監聽頁面隱藏 */ onHide: function () {  }, /** * 生命周期函數--監聽頁面卸載 */ onUnload: function () {  }, /** * 頁面相關事件處理函數--監聽用戶下拉動作 */ onPullDownRefresh: function () {  }, /** * 頁面上拉觸底事件的處理函數 */ onReachBottom: function () {  }, /** * 用戶點擊右上角分享 */ onShareAppMessage: function () {  }, //適配不同屏幕大小的canvas setCanvasSize: function (width) { var size = {}; try {  var res = wx.getSystemInfoSync();  var scale = 750 / width;//不同屏幕下canvas的適配比例；設計稿是750寬  // var scale = 1  var width = res.windowWidth / scale;  var height = res.windowHeight / scale;;  size.w = width;  size.h = height; } catch (e) {  // Do something when catch error  console.log("獲取設備信息失敗" + e); } return size; }, //點擊圖片進行預覽，長按保存分享圖片 previewImg: function (e) { var img = this.data.img; let _this = this; //保存二維碼到相冊 wx.saveImageToPhotosAlbum({  filePath: img,  success: function (res) {  wx.showModal({   content: '保存成功',   confirmText: '確認',   showCancel: false,   success: function (res) {   }  });  },  fail: function (res) {  wx.showModal({   content: '保存失敗',   confirmText: '確認',   showCancel: false,   success: function (res) {   }  });  } }) }, })