PNG vs JPG
JPGs
- Photographs
- Landscapes
- Faces
JPGs are “ lossy ,” which means they throw away aspects of the image that the human eye won’t see. The JPG “Quality” determines how much of the image is discarded.
PNGs
- Charts
- Graphs
- Screenshots
- Cartoons
PNGs are “ lossless ,” which means they keep all aspects of the image, include those that the human eye might not see. The can also contain “ transparent ” regions.
GIFs
- Cartoons
- Sparingly
Use JPGs for photographs, landscapes, and faces. Use PNGs for charts, graphs, screenshots and cartoons. Use GIFs only for animations, and sparingly. ~ Scott Hanselman
See
http://www.hanselman.com/blog/BloggersKnowWhenToUseAJPGAndWhenToUseAPNGAndAlwaysSquishThemBoth.aspx