Data Compression


Criteria

Survey Formats

Basics

Compression Methods

Data Formats

Files

Audio Data

Image Data

GIF

Colours

Data Compression

Characteristics

GIF87a

GIF89a

Patents

Optimizations

Examples

Drawings

JPEG

Video Data


Glossary

Index


Download


www.BinaryEssence.com

GIF - Examples


To demonstrate the effects of the different colour tables on the file size, the BinaryEssence logo has been encoded correspondingly.


Examples: File sizes depending on the total number of colours


Number of Colours Index Type of the Table File Size
4 2 bit optimized 1,612 byte
8 3 bit optimized 1,994 byte
16 4 bit optimized 2,387 byte
256 8 bit Standard 5,569 byte


At the given examples only insignificant deviations result in the subjective quality of the presentation:


optimized, 4 colours, 1,612 byte


optimized, 8 colours, 1,994 byte


optimized, 16 colours, 2,387 byte


Standard table of MS-Paint, 256 colours, 5,569 byte



optimized
4 colours
1,612 byte
optimized
8 colours
1,994 byte
optimized
16 colours
2,387 byte
standard table
256 colours
5,569 byte


The savings seem to be small (3,957 byte, 256 versus 4 colours), but for larger files and looking to the entire data volume transferred from a website, a remarkable amount of data results. The maximum reduction potential is approximately 71% in this example.


Beside the total amount of data the access time should be taken into consideration. A large number of users do not have fast internet access, slow modems are still in use. Additionally overloaded servers are not a rare phenomenon. This unnecessary load does not offer any advantage, it only consumes time and money.


Websites with large pictures or a variety of logos and buttons sometimes require intolerable access times. Potential users may break off the page setup, what is definitely not intended especially for commercial websites.


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GIF - Graphic Interchange Format GIF - Anti-Aliasing GIF - Drawings