<button open-type="contact" bindcontact="handleContact" session-from="sessionFrom">客服</button>

{
  "permissions": {
    "openapi": [
      "wxacode.get",
      "customerServiceMessage.send",
      "customerServiceMessage.uploadTempMedia"
    ]
  }
}

const cloud = require('wx-server-sdk')
cloud.init()
// 下載云存儲(chǔ)圖片
// 講圖片上傳到小程序云開(kāi)發(fā)的存儲(chǔ)中可以得到文件的fileID
let downLoad = async(event, context) => {
    const res = await cloud.downloadFile({
        fileID: 'cloud://example.png' 
    })
    const buffer = res.fileContent
    return buffer
}
// 把媒體文件上傳到微信服務(wù)器
let upload = async(Buffer) => {
    return await cloud.openapi.customerServiceMessage.uploadTempMedia({
        type: 'image',
        media: {
            contentType: 'image/png',
            value: Buffer
        }
    })
}
// 云函數(shù)入口函數(shù)
exports.main = async (event, context) => {
  // 客服消息
  if (event.MsgType == 'event') {
    const wxContext = cloud.getWXContext()
    let Buffer = await downLoad()
    let meida = await upload(Buffer)
    await cloud.openapi.customerServiceMessage.send({
        "touser": wxContext.OPENID,
        "msgtype": "image",
        "image": {
            "media_id": meida.mediaId
        }
    })
    return "success"
  }
};

// cloud = require('wx-server-sdk')
// ...
// 方法返回 Promise
cloud.openapi.customerServiceMessage.uploadTempMedia({
  type: 'image',
  media: {
    contentType: 'image/png',
    value: Buffer
  }
})

wx.cloud.downloadFile({
  fileID: 'a7xzcb'
}).then(res => {
  console.log(res.data)
}).catch(error => {
  // handle error
})