1. 调用wx.chooseImage 选择图片

2.wx.uploadFile 上传图片

3.调用后台接口进行修改操作 修改原来的头像

wx.chooseImage({
  success: function(res) {
    var tempFilePaths = res.tempFilePaths
    wx.uploadFile({
      url: \'https://\', //接口地址
      filePath: tempFilePaths[0],
      name: \'file\',
      formData:{
        \'user\': \'test\'
      },
      success: function(res){
        var data = res.data
        //do something
      }
    })
  }
})

https://www.cnblogs.com/LCH-M/p/9420482.html#4408245