minecraft-assets/data/minecraft/recipes/purple_carpet_from_white_carpet.json

{
  "type": "minecraft:crafting_shaped",
  "group": "carpet",
  "pattern": [
    "###",
    "#$#",
    "###"
  ],
  "key": {
    "#": {
      "item": "minecraft:white_carpet"
    },
    "$": {
      "item": "minecraft:purple_dye"
    }
  },
  "result": {
    "item": "minecraft:purple_carpet",
    "count": 8
  }
}