Data Compression


Criteria

Survey Formats

Basics

Compression Methods

Data Formats

Files

Audio Data

Image Data

GIF

Colours

Data Compression

Characteristics

GIF87a

GIF89a

Patents

Optimizations

Colour Tables

Optimized Tables

Standard Tables

Raster

Anti-Aliasing

Examples

Drawings

JPEG

Video Data


Glossary

Index


Download


www.BinaryEssence.com

GIF - Anti-Aliasing


Anti-aliasing is a procedure reducing the visible stair effects of lines or edges. The algorithm inserts intermediate steps, which shall "blur" the transition between two pixels. In the view of the entire picture thereby a better image quality is given.


This does not lead always to success, because the additional blurring may be subjectively considered as a quality impairment. Regarding GIF primarily two effects arise:


The intermediate steps possibly require additional colours expanding the total amount of colours. Monochromatic images originally encoded with two indices need one additional colour at least. That doubles the size necessary to address the colour table. The logo of BinaryEssence is encoded in this manner using four colours, but their usage was manually adapted to get the best possible result.


Due to this additional picture contents, the compression efficiency decreases. That is also caused by the intermediate steps, which has to be included into the sequence table. In general the size of the sequence tables will be enlarged and in parallel larger index addresses are necessary.


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GIF - Optimizations GIF - Raster GIF - Examples