"What Is GIF?" Compuserve; May 28, 1987
Info on the .GIF file format. Posted by: Jim The Eagle
Introduction
CompuServe has developed a new Graphics Interchange Format
(GIF) designed to serve a wide variety of graphics needs both
within the CompuServe product environment and as a universal
standard by which graphics can be exchanged between any parties
through a network. This document serves as a simple explanation
of what GIF is and what it is capable of.
What is GIF?
GIF (pronounced "Jif") is a mechanism of storing high-quality
color graphics images in a way that can be exchanged between users
of differing hardware. For example it allows images created on an
Atari ST to be displayed on a Commodore Amiga or IBM-PC and visa
versa. The GIF format allows for very high resolution, full color
images that can be used in any application that requires the
display of graphics information.
What Kind of Images can GIF be Used For?
GIF images can be part of, but not limited to the following
applications:
- Full color associate photo board
- Business charts and graphics
- Merchandise catalogs
- Technical documentation
- Schematic diagrams for field service personnel
- Color radar maps
- Medical illustrations
- Art gallery
- Exchange of user-created images
How Much Resolution Can an Image Have?
In terms of pixels, or image dots, GIF is capable of defining
images of over 16,000 by 16,000 individual dots. This compares
with the average microcomputer screen of 320 by 200 pixels. Even
laser printers are generally limited to about 2000 by 3000 pixels.
GIF technology is adequate for graphics applications for years to
come.
How Many Colors Can a GIF Image Have?
Any GIF image can have up to 256 simultaneous colors
contained within it. Each individual color can be defined out of
a possible set of 16 million colors, making photographic-quality
images possible.
Does This Mean an IBM-PC Cannot Display GIF Images with 256 Colors?
All GIF images can be processed by all GIF software. The
software is designed to make the best use of a specific
hardware's capabilities with regard to colors. A best match is
made between a desired color in the image, and the possible colors
the hardware can display. Generally, detail of an image will be
lost, but it should still be recognizable. On the other side,
any image originating from an IBM machine should display exactly
on a more capable microcomputer.
How Large are the Image Files in GIF?
This will vary a great deal depending on the number of colors
present, the size of the image and the amount of detail present.
GIF uses a sophisticated compression method that reduces the file
size to between 1/2 to 1/8 of the original file size of the image.
This means that even complex images can be economically
downloaded. An example is an Atari ST image file of 320 by 200
pixels and 16 colors which would require 32,000 bytes on the Atari
might only require 8,000 bytes in GIF format, a space savings of 4
to 1.
What Micros can Support GIF?
Currently CompuServe has developed software for a number of
microcomputers to display or create GIF format files. Additional
hardware will be supported as time goes on. The GIF standard
document will be made public and third party authors will be
encouraged to create additional GIF software for other hardware.
Machines supported currently include:
- IBM-PC/MS-DOS family with CGA or EGA graphics boards
- Commodore Amiga
- Atari ST
- Macintosh family
The software files can be found in the appropriate hardware
FORUMS and in the Picture Support Fourm (GO PICS).
Where are the GIF Files that can be Displayed?
Currently many GIF files are available in DL2 of the Picture
Support Forum. Each appropriate hardware forum will also
accumulate GIF files as time goes on. The CompuServe FORUM
software has a GIF file type established for uploads of GIF image
files.