記事「Node-REDでSlackへ画像を投稿する」と記事「ラズパイ+Node-REDでオムロン製「環境センサ」（USB型）のデータをBLE経由で取得して可視化する」を組み合わせて、パトランプなどの光を検知するとSlackで通知する方法について説明します。

Slackの準備

Slackの準備は、以下の記事を参考にしてください。

今回は、ワークスペース「Node-RED開発」のチャンネル「node-red_alert」に画像を投稿します。

Node-REDによるフローの作成

記事「ラズパイ+Node-REDでオムロン製「環境センサ」（USB型）のデータをBLE経由で取得して可視化する」のフローに、光を検知したときにSlackへメッセージとUSBカメラで撮影した画像を通知するためのフローを作成します。

node-red-contrib-usbcameraのインストール

Node-REDをWebブラウザで開きます。
右上にある「三」のボタンをクリックしてメニューを開き、「パレットの管理」をクリックします。
「ノードの追加」タブを選択して、検索のテキストボックスに「usbcamera」と入力します。
検索されたノードから「node-red-contrib-usbcamera」の「ノードを追加」ボタンをクリックします。
パレットの「Raspberry Pi」グループにノードが追加されます。

node-red-contrib-slackのインストール

「ノードの追加」タブを選択して、検索のテキストボックスに「slack」と入力します。
検索されたノードから「node-red-contrib-slack」の「ノードを追加」ボタンをクリックします。
パレットの「ソーシャル」グループにslackのノードが4つ追加されます。

モジュールのインストールと設定

Slackへ画像を投稿するには、画像をStreamオブジェクトで読み込みます。
そのため、Node.jsのfsモジュール（ファイルストリームモジュール）をインストールして、functionノードで利用できるように設定します。

fsモジュールをインストールします。
Windowsは、コマンドプロンプトを管理者で実行、Raspberry PiなどのLinux系は、ターミナルを実行し、次のコマンドを入力します。

Windows

> npm install fs

Linux

$ cd ~/.node-red
$ npm install fs

settings.jsファイルを編集します。fsライブラリが利用できるように、次の一行を追加します。ファイルの場所は以下のとおりです。
- Windowsの場合: C:\Users\ユーザー名\.node-red\settings.js
- Linux系の場合: $HOME/.node-red/settings.js

settings.js

functionGlobalContext: {
+   fs:require('fs'),
    // os:require('os'),
},

Node-REDを再起動します。

ノードの設定

Node-REDのワークスペースに以下のノードを追加し、図のように配置します。
- switchノード
- usbcameraノード
- functionノード
- slack-web-outノード
- debugノード
switchノードの左側のポートは、buffer parserノードの照度の値を取得する3番目のポートに接続します。
室内の照度は700lx以下なので、環境センサで測定した照度が1000lxより大きくなった場合、光を検知したと判断するようにします。
switchノードをダブルクリックし、以下の設定をして「完了」ボタンをクリックします。
- 名前: 「照度 > 1000」と入力
- 条件: 「>」を選択, 「数値」を選択, 「1000」と入力
usbcameraノードをダブルクリックし、以下の設定をして「完了」ボタンをクリックします。
- File Name: 「image.jpg」と入力
- Image Resolution: 「640x480」を選択
functionノードをダブルクリックして、以下のコードを入力します。

functionノード

const fs = global.get('fs');  // fsモジュールを参照
const filepath = "/home/gitc/Pictures/image.jpg";  // 画像ファイルの絶対パス

msg.topic = "files.upload";
msg.payload = {
    "channels": "node-red_alert",
    "initial_comment": "光を検知しました。",
    "filename": filepath,
    "file": fs.createReadStream(filepath),  // 画像ファイルのStreamオブジェクトを生成
    "filetype": "auto"
};

return msg;

slack-web-outノードをダブルクリックして、「新規にslack-configを追加」をクリックします。

「slack-config」が既に登録されている場合は、その項目を選択してください。
Slackアプリのトークンを貼り付け、「追加」ボタンをクリックします。
「完了」ボタンをクリックします。
「デプロイ」ボタンをクリックします。
完成したフローです。

作成したフローのJSONを以下に貼っておきます。
Node-REDのメニューから「読み出し」->「クリップボード」で配置することができます。
slack-web-outノードのTokenは再設定してください。

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動作確認

ラズベリーパイにUSBカメラを接続して、画像を撮影したい場所に配置します。

パトランプなどに環境センサが光を検知するように取り付けます。パトランプが点灯して光を検知すると照度が1000以上になるので、USBカメラの画像を撮影して、Slackにメッセージを送信します。
Slackアプリで、光を検知した時刻とUSBカメラで撮影した画像を確認することができます。

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