Open the file in Preview, go to the File menu, and choose Save As…, where
you can export your graphic in Photoshop, JPEG, PICT, BMP (for sharing files
with PC users), PICT, Targa (for video), and more. If the format you’re
saving in has options (such as quality and compression settings for JPEG and
TIFF images), they will appear near the bottom of the dialog.
Lee