Medium: https://medium.com/@dnicolas/learn-how-to-automate-your-images-optimization-process-with-lepto-ad2cf89e2a31

lepto.config.json

{
  "input": "assets",
  "output": "assets/output",
  "watch": true,
  "filters": [
    {
      "glob": "**/*.*",
      "use": [
        {
          "name": "lepto.jpeg",
          "quality": 75
        },
        {
          "name": "lepto.png",
          "quality": 75
        }
      ]
    }
  ]
}