TransformPicture is a utility for scaling, rotating and converting pictures. You can scale pictures by a given percentage or by specifying the pixel width or height of the resultant image. You can also simultaneously convert to other graphic formats: PNG, BMP, TIFF, JPEG, JPEG200, GIF and PICT.
Use the preferences window to configure various options.
Once you have specified the desired preferences simply drop multiple files or folders onto the application in the Finder, or onto the main window to process pictures in batch.