GIF, JPG, PNG

Now that you know something about RGB color, and lossy compression, you are ready to understand differences between common image formats. Many of these differences revolve around differences in compression and how color is handled.

Here I compare the three most common image formats in use today. Each has advantages and disadvantages.
GIF (pronounced with a soft g, like JIFF peanut butter) was introduced in 1987. It stands for Graphics Interchange Format.
JPG was introduced in 1992 and stands for Joint Photographics Experts Group. The acronym JPEG is often shortened to 3 letters.
PNG, introduced in 1996, is open-source. Officially, it stands for Portable Network Graphic, but unofficially it stands for "png’s not gif". As the official and unofficial names suggest, PNG is especially well suited to the network, rather than print, and was designed to replace the proprietary GIF format. In addition to providing an open source alternative to GIF, PNG supports an unlimited number of colors and is suitable for color photographs.

Compression

JPG supports an unlimited number of colors suitable for color photographs. However, every time you modify and save a JPG image, the quality degrades because of the lossy compression. If you are saving artwork to work on later, PNG is a better format because you do not lose any quality.

File size

A benefit of JPG's lossy compression algorithm, is that it achieves file sizes about one-fifth the size of a comparable PNG. However, a benefit of GIF is that it readily supports transparency and animation, neither of which are supported by JPG. PNG offers full and partial transparency, which improves on GIF. However, PNG's animation is not as widely supported as GIF.

Watch this 3.15-minute video clip comparing the different image formats.

DSP 2 (10 pts): compression & image formats