GRAPHIC FILE FORMATS
are descriptions of some
commonly used file formats:
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.
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.
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.
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.
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.