[Unity] Terrainのアルファマップをpngファイルに出力する

TerrainAlphamapToPNG.cs

using System.IO;
using UnityEngine;
using UnityEditor;

public class TerrainAlphamapToPNG : Editor
{
    [MenuItem("Assets/Create/TerrainPNG")]
    static void Create()
    {
        TerrainData terrainData = (TerrainData)Selection.activeObject;
        Texture2D[] textures = terrainData.alphamapTextures;

        string directory = "TerrainAlphaMaps/" + terrainData.name;
        if (!Directory.Exists(directory)) {
            Directory.CreateDirectory(directory);
        }

        for (int i = 0; i < textures.Length; i++) {
            Texture2D texture = textures[i];
            byte[] texData = texture.EncodeToPNG();

            string filePath = directory + "/" + texture.name + ".png";
            File.WriteAllBytes(filePath, texData);
        }

        EditorUtility.OpenWithDefaultApp(directory);
    }


    [MenuItem("Assets/Create/TerrainPNG", true)]
    static bool IsTerrainData()
    {
        return Selection.activeObject != null && Selection.activeObject is TerrainData;
    }
}