微信小程序如何使用canvas二维码保存至手机相册

//
 const _this=this;
   wx.getSystemInfo({
    success (res) {
     _this.drawCanvas(res.windowHeight);
    }
   })
	 
drawCanvas(height) {
//这里的canvas的高是动态获取设备的高度，做到自适应
    const that = this;
   let heightVal=height*2+'rpx';
   this.imgDraw = {
    width: '750rpx',
    height: heightVal,
    background: '#fff',
    views: [
     {
      type: "rect",
      css: {
       top: '20rpx',
       left: '130rpx',
       color: '#1A1A1A',
       width: '660rpx',
       height: '220rpx',
       borderRadius: '32rpx'
      }
     },
     {
      type: 'image',
      url: './a.jpg',
      css: {
       top: '36rpx',
       left: '16rpx',
       width: '188rpx',
       height: '188rpx'
      }
     },
     {
      type: 'text',
      text: '',
      css: {
       top: '54rpx',
       left: '260rpx',
       fontSize: '48rpx',
       color: "#fff"
      }
     },
     {
      type: 'text',
      text: '文字部分',
      css: {
       top: '134rpx',
       left: '260rpx',
       fontSize: '30rpx',
       color: "#d1d1d1"
      }
     },
     {
      type: 'text',
      text: '1333333333',
      css: {
       top: '196rpx',
       left: '260rpx',
       fontSize: '26rpx',
       color: "#d1d1d1"
      }
     },
     {
      type: 'text',
      text: '李四',
      css: {
       top: '304rpx',
       left: '302rpx',
       fontSize: '24rpx',
       color: "#767676"
      }
     },
     {
      type: 'image',
      url: '/icon-localtion.png',
      css: {
       top: '275rpx',
       left: '260rpx',
       width: '26rpx',
       height: '168rpx'
      }
     },
     {
      type: 'image',
      url: '二维码.png',
      css: {
       top: '646rpx',
       left: '236rpx',
       width: '278rpx',
       height: '278rpx'
      }
     }
    ]
   }

  
   let { path: __path } = mpvue.getStorageSync('createImagePath')
   mpvue.saveImageToPhotosAlbum({
    filePath: __path,
    success(res) {
     // mpvue.showToast({
     //  title: '保存成功',
     //  icon: 'success',
     //  duration: 800,
     //  mask: true
     // });
   
    },
    fail(res) {
     // mpvue.showToast({
     //  title: '保存失败',
     //  icon: 'fail',
     //  duration: 800,
     //  mask: true
     // });
    }
   });
  },

let { path: __path } = mpvue.getStorageSync('createImagePath')
mpvue.saveImageToPhotosAlbum({
 filePath: __path,
 success(res) {
  // mpvue.showToast({
  //  title: '保存成功',
  //  icon: 'success',
  //  duration: 800,
  //  mask: true
  // });

 },
 fail(res) {
  // mpvue.showToast({
  //  title: '保存失败',
  //  icon: 'fail',
  //  duration: 800,
  //  mask: true
  // });
 }
});