COMMON GRAPHIC FILE FORMATS

Following are descriptions of some
commonly used file formats:

GIF: The Graphics Interchange Format was originally developed by CompuServe in 1987. It is most commonly used for bitmap images composed of line drawings or blocks of a few distinct colors. The GIF format supports 8 bits of color information or less. In addition, the GIF89a file format supports transparency, allowing you to make a color in your image transparent. This feature makes GIF a particularly popular format for Web images.

JPEG: Like GIF, the Joint Photographic Experts Group format is one of the most popular formats for Web graphics. It supports 24 bits of color information, and is most commonly used for photographs and similar continuous-tone bitmap images. The JPEG file format stores all of the color information in an RGB image. JPEG was designed so that changes made to the original image during conversion to JPEG would not be visible to the human eye. Most imaging applications let you control the amount of lossy compression performed on an image, so you can trade off image quality for smaller file size and vice versa. Be aware that the chances of degrading your image when converting it to JPEG increase proportionally with the amount of compression you use. Unlike GIF, JPEG does not support transparency.

BMP: The Bitmap file format is used for bitmap graphics on the Windows platform only. Unlike other file formats the BMP format stores image data from bottom to top and pixels in blue/green/red order. Compression of BMP files is not supported, so they are usually very large.

TIFF: The Tag Interchange File Format is a tag-based format that was developed and maintained by Aldus (now Adobe). TIF, which is used for bitmap images, is compatible with a wide range of software applications and can be used across platforms such as Macintosh, Windows, and UNIX. The TIFF format is complex, so TIFF files are generally larger than GIF or JPEG files. TIFF supports lossless LZW (Lempel-Ziv Welch) compression; however, compressed TIFFs take longer to open.

PNG: The Portable Network Graphics format will likely be the successor to the GIF file format. PNG is expected to become a mainstream format for Web images and could replace GIF entirely. It is platform independent and should be used for single images only (not animation). Compared with GIF, PNG offers greater color support and better compression, gamma correction for brightness control across platforms, better support for transparency, and a better method for displaying progressive images.

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