This service will be available in Finder's Services menu and contextual menu if image files are selected. It enables you to batch resize images by simply entering the number of pixels required in the new images' width or by indicating the percentage required of the original size. The resulting images are created preserving the width to height ratio. Supported formats include: BMP, GIF, JPEG, JPEG 2000, PDF, PICT, PNG and TIFF. Note that the location you choose for the resulting images must be different from that of the originals.
