Node-REDのフローに画像ファイルなどを埋め込む

#はじめに
Node-REDを他のソフトウェアと連携させて使っていると、文字だけでなく画像ファイルを出力させたくなります。
大きなファイルはファイルシステム上にファイルを置いて、「file」ノードを使えばいいのですが、アイコンやロゴなどの小さい容量のファイルであれば、フロー内に埋め込んでしまう事ができます。
フローに埋め込むと、コードの書き出し/読み込みで画像も移植できるというメリットがあります。

#前提環境
- Node-RED v1.0.3

#フローの作成

今回はkubernetesのロゴ画像を扱います。
ロゴ画像はBASE64形式の文字列でテンプレートノードに記載します。BASE64形式へのエンコードは、Linux系OSであればbase64コマンドでできます。
あとは、functionノードで１行デコード処理にかけるだけです。

![スクリーンショット 2020-01-13 0.40.32.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/410957/cba3a5e8-42b8-c726-bcc2-442ee5304f7e.png)

```
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in","z":"f4557e75.b0f3f","name":"","url":"/kube.png","method":"get","upload":false,"swaggerDoc":"","x":560,"y":40,"wires":[["164563bd.70ad9c"]]},{"id":"62a0a06c.8b5e4","type":"function","z":"f4557e75.b0f3f","name":"BASE64 to Buffer","func":"\nmsg.payload = new Buffer.from(msg.image,'base64');\n\nreturn msg;","outputs":1,"noerr":0,"x":950,"y":40,"wires":[["93fc355a.0fff28"]]},{"id":"93fc355a.0fff28","type":"http response","z":"f4557e75.b0f3f","name":"","statusCode":"200","headers":{"content-type":"image/png"},"x":1130,"y":40,"wires":[]}]
```

私はKibanaで可視化をする際に、このテクニックをよく使います。
単純にMarkdownでダッシュボードに画像を貼り付けたり、Enable/Disableを画像で可視化するような場合の参照先として、Node-REDの画像を参照させています。

![スクリーンショット 2020-01-13 0.55.17.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/410957/a52adb9e-3363-5f37-0029-35ec8d039619.png)