http://www.applemacsoft.com/ -Mac Graphic Converter is an easy to use and powerful batch image converter and photo resizer, that supports more than 50 graphic formats including GIF, JPG, PNG, BMP, PSD, Digital Photo RAW formats and many others.You can use it to convert multiple graphic files from different formats to desired format in one time.
http://www.applemacsoft.com/graphic-converter/index.html