Batch Image Conversion in Mac OS X the Easy Way with Preview
Preview is a greatly under-appreciated app that has been bundled along with Mac OS X since the beginning, getting better and better with each Mac OS release. One quiet feature that has been around for a while is the ability to mass convert a group of pictures from one file type to another, often referred to as batch conversion. This lets you easily take a large amount of JPG files and convert them over to PNG, for example.
Batch image conversion works with any number of image files and with nearly any image formats. It’s safe to assume that if you can open the image files into Preview app, you can export them to a new file type, including GIF, ICNS, JPEG, JPEG-2000, BMP, Microsoft Icon, OpenEXR, PDF, Photoshop PSD, PNG, SGI, TGA, and TIFF.