想通过canvas画一张海报，但是获取的图片base64编码无法画到canvas上，现在将base64图片临时保存，但是临时保存的路径无法正常访问是什么原因？

async initCanvas() {
      let systemInfo = await this.getSystemInfo();
      this.ctx = uni.createCanvasContext('firstCanvas');  
      this.ctx.drawImage('/userPages/static/share/share.jpg', 0, 0, systemInfo.windowWidth, systemInfo.windowHeight);
      let qrcodePath = await this.getBase64ImageInfo()
      this.ctx.drawImage(qrcodePath, 0, 0, 216, 216);
      this.ctx.draw()
    },
    getBase64ImageInfo() {
      const fs = uni.getFileSystemManager()
      var times = new Date().getTime();
      var imgPath = wx.env.USER_DATA_PATH + '/share.png';
      return new Promise((req, rej) => {
        fs.writeFile({
          filePath: imgPath,
          data: this.share.icon.slice(22),
          encoding: 'base64',
          success: (res) => {
            this.textImg = imgPath
            req(imgPath)
          }
        })


      })
    },

这个时候报500错误，图片访问不到，base64真实可以用的