File Types

When we create an image and want to post it on the Internet we want our image to be accessible to all viewers. We wouldn't want to post a (.psd) or a (.tiff) file onto a webpage because most Web browsers can not display that file type. Different web browsers can support different file formats, but there are three main file types that are supported by nearly all web browsers. these are: .JPG, .GIF, and .PNG

.JPG
Almost everyone has used or come across this file format before. (.jpg) also known as (.jpeg) stands for Joint Photographic Experts Group , which was the name of the committee which created the file format.

JPG is a method of compression for photographic images. Because its compression works so well in maintaining the quality of the original photograph JPG is the format most commonly used for storing and transmitting photographs on the Internet. It uses quantization in its compression, reducing the amount of information by approximating small differences in color. Another reason JPGs are so frequently used with photographs is that a JPG images can support 24 bit color information (16 million different colors) and are not limited like GIFs to only 256 colors.

JPG also gives you the option to choose the quality of the compression. The original image was 350 kb

.GIF
Graphics Interchange Format (GIF) files, pronounced "JIF," are a bitmap image format that can support up to 256 colors. CompuServe introduced the format in 1987 in order to provide a color image format for their file downloading areas. GIFs became popular because it used LZW data compression, which was more efficient than the run-length encoding that formats such as PCX and MacPaint that were also used at the time. With the use of .GIF files, fairly large images could be downloaded in a reasonable amount of time, even with very slow modems. (remember we are talking about early 90's here, no cable modems yet)

Probably the most useful function of the GIF formats today is its ability to store multiple images in one file. By showing multiple images sequentially we perceive it as a moving animation.

Animated GIFs are just several still frames played in succession

.PNG
Portable Network Graphics (PNG) files are a bitmap image format similar to the GIF with the exception that they do not require a patent license to use and they can also support millions of colors instead of GIFs 256. However, PNGs do not support animation, and until recently were not as widely supported by web browsers as GIFs.

PNG-8 supports both 8 bit color (256 colors) and 24 bit color (millions of colors)

PNGs were created to improve and replace the GIF format