{
  "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",
  "elmType": "div",
  "children": [
    {
      "elmType": "div",
      "style": {
        "margin": "2px",
        "width": "48px",
        "height": "48px",
        "overflow": "hidden",
        "border-radius": "50%"
      },
      "children": [
        {
          "elmType": "a",
          "attributes": {
            "href": "='https://twitter.com/' + @currentField",
            "target": "_blank"
          },
          "children": [
            {
              "elmType": "img",
              "attributes": {
                "src": "='https://twitter.com/' + @currentField + '/profile_image?size=normal'",
                "title": "='@' + @currentField",
                "alt": "='@' + @currentField"
              },
              "style": {
                "position": "relative",
                "top": "50%",
                "left": "50%",
                "width": "100%",
                "height": "auto",
                "margin-left": "-50%",
                "margin-top": "-50%"
              }
            }
          ]
        }
      ]
    }
  ]
}