Unity customized gadget "export atlas pictures"

public class TestSaveSprite
{
    [MenuItem("Tools/ Export Wizard ")]
    static void SaveSprite()
    {
        string resourcesPath1 = "Assets/ResourcesOut/ui/atlas";
        foreach (Object obj in Selection.objects)
        {
            string selectionPath = AssetDatabase.GetAssetPath(obj);

            if (selectionPath.StartsWith(resourcesPath1))
            {
                string selectionExt = System.IO.Path.GetExtension(selectionPath);
                if (!selectionExt.Equals(".prefab"))
                {
                    continue;
                }

                UIAtlas Atlas = UnityEditor.AssetDatabase.LoadAssetAtPath<UIAtlas>(selectionPath);
                string outPath = Application.dataPath + "/outSprite/" + Atlas.name;
                ExportTexturePNGFromAtlas(outPath, Atlas);
                AssetDatabase.Refresh();
            }
        }

        Debug.Log("SaveSprite Finished");
    }

    static void ExportTexturePNGFromAtlas(string folderPath, UIAtlas atlas)
    {
        List<UISpriteData> exitSpritesList = atlas.spriteList;
        Texture2D atlasTexture = NGUIEditorTools.ImportTexture(atlas.texture, true, false, !atlas.premultipliedAlpha);
        int oldwith = atlasTexture.width;
        int oldHeight = atlasTexture.height;
        Color32[] oldPixels = null;
        foreach (var es in exitSpritesList)
        {
            // Limit es.x stay 0 ~ oldwith Between 
            int xmin = Mathf.Clamp(es.x, 0, oldwith);
            // Limit es.y stay 0 ~ oldHeight Between 
            int ymin = Mathf.Clamp(es.y, 0, oldHeight);
            // Limit es.width stay 0 ~ oldwith  Between 
            int newWidth = Mathf.Clamp(es.width, 0, oldwith);
            // Limit es.width stay 0 ~ oldHeight  Between 
            int newHeight = Mathf.Clamp(es.height, 0, oldHeight);

            if (newWidth == 0 || newHeight == 0) continue;
            // obtain 32 Bit pixel color list 
            if (oldPixels == null) oldPixels = atlasTexture.GetPixels32();
            Color32[] newPixels = new Color32[newWidth * newHeight];
            for (int y = 0; y < newHeight; ++y)
            {
                for (int x = 0; x < newWidth; ++x)
                {
                    int newIndex = (newHeight - 1 - y) * newWidth + x;
                    int oldIndex = (oldHeight - 1 - (ymin + y)) * oldwith + (xmin + x);
                    newPixels[newIndex] = oldPixels[oldIndex];
                }
            }

            Texture2D t = new Texture2D(newWidth, newHeight);
            t.SetPixels32(newPixels);

            t.Apply();
            byte[] bytes = t.EncodeToPNG();
            Texture2D.DestroyImmediate(t);
            t = null;
            if (!Directory.Exists(folderPath))
            {
                Directory.CreateDirectory(folderPath);
            }

            using (FileStream fs = new FileStream(folderPath + "/" + es.name + ".png", FileMode.CreateNew))
            {
                BinaryWriter writer = new BinaryWriter(fs);
                writer.Write(bytes);
            }
        }
    }
}