void OnFocus()
        {
            if (ditherMapGenerator == null)
            {
                if (s_ditherMapGenerator == null)
                {
                    s_ditherMapGenerator = new DitherMapGenerator();
                }
                ditherMapGenerator = s_ditherMapGenerator;
                ditherMapTexture   = ditherMapGenerator.CreateTexture(16);

                serializedObject  = new SerializedObject(this);
                generatorProperty = serializedObject.FindProperty("ditherMapGenerator");
                // textureProperty = serializedObject.FindProperty ("ditherMapTexture");
            }
        }
        void OnGUI()
        {
            EditorGUI.BeginChangeCheck();
            EditorGUILayout.PropertyField(generatorProperty, true);
            if (EditorGUI.EndChangeCheck())
            {
                serializedObject.ApplyModifiedProperties();
                ditherMapGenerator.iteration = ditherMapGenerator.iteration;
                ditherMapGenerator.Apply(ditherMapTexture);
            }

            EditorGUILayout.LabelField(string.Format("Dither Map Texture: Size = {0}x{0}", ditherMapGenerator.dimensions));

            EditorGUILayout.BeginHorizontal();
            if (GUILayout.Button("Export PNG"))
            {
                var size = ditherMapGenerator.dimensions;
                var tmp  = ditherMapGenerator.CreateTexture(size);
                EditorUtil.SaveAsPNG(tmp, "new dither map texture");
            }
            if (GUILayout.Button("Export JPG"))
            {
                var size = ditherMapGenerator.dimensions;
                var tmp  = ditherMapGenerator.CreateTexture(size);
                EditorUtil.SaveAsJPG(tmp, "new dither map texture");
            }
            if (GUILayout.Button("Copy string"))
            {
                EditorGUIUtility.systemCopyBuffer = DitherMapGenerator.GetString(ditherMapGenerator.iteration);
            }
            EditorGUILayout.EndHorizontal();

            GUI.enabled = false;
            var resolution = Mathf.Min(position.width, position.height - EditorGUI.GetPropertyHeight(generatorProperty, true)) - 46f;

            EditorGUILayout.ObjectField(ditherMapTexture, typeof(Texture2D), false, GUILayout.Height(resolution), GUILayout.Width(resolution));
            GUI.enabled = true;
        }