Data Compression


Criteria

Survey Formats

Basics

Compression Methods

Data Formats

Files

Audio Data

Image Data

GIF

JPEG

Characteristics

Fields of Application

Coding Steps

Image Preparation

Transformation

Quantization

Entropy Coding

Compatibility

Video Data


Glossary

Index


Download


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JPEG: Quantization (Weighting of the Contents)


The result of the DCT is a set of values also describing the image contents. In contrast to the original format they do not affect the image quality in the same manner. The reason is the subjectively different perception of details.


With the help of quantization more relevant values are described with a higher accuracy. Values influencing the subjective perception to a smaller extend will be devalued and represented with lower range of values.


Quantization is not reversible and substantially affects the image quality.


The quantization is processed with special tables which will be stored within the corresponding JPEG file. They are essential for decoding.


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JPEG: Coding Steps JPEG: Transformation (Discrete Cosine Transform, DCT) JPEG: Entropy Coding (Huffman Coding)