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