public GameObject[] prefab;//模型对象
  
    void Start()
    {
        for (int i = 0; i < prefab.Length; i++)
        {
            EditorUtility.SetDirty(prefab[i]);
            Texture2D image = AssetPreview.GetAssetPreview(prefab[i]);
            //下面这里是图片的导出地址
            System.IO.File.WriteAllBytes(Application.dataPath +                     "/Resolution/image_"+i+".png", image.EncodeToPNG());
        }
        
    }