wx.downloadFile ({
  url: 'http://qctm-assets.oss-cn-beijing.aliyuncs.com/newagent/reference_bg.png',
  success(res){
    imagesBg = res.tempFilePath
    wx.setStorage({
      key: 'imagesBg',
      data: imagesBg,
    });
    const ctx = wx.createCanvasContext('myCanvas')
    ctx.drawImage(imagesBg, 0, 0, 150, 100)
    ctx.draw()
    console.log('绘制成功');
  },
})

使用downloadFile将网络图片转化为本地临时文件，绘制到canvas，图片不显示，也不报错