静态函数
| UploadImage | Uploads an image |
| DownloadImage | Downloads an image through its URL, and then converts it to the Texture2D texture |
| DownloadImageByURI | Downloads an image through its URI, and then converts it to the Texture2D texture |
| UnloadImageByURI | Unloads an image |
| UnloadImage | Unloads an image by URI |