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Figure 7.12 and the above JPEG components have described how
compression is achieved at several stages. Let us conclude by summarising
the overall compression process:
- A
"Frame" is a picture, a "scan" is a pass through the pixels (e.g., the red
component), a "segment" is a group of blocks, a "block" is an 8x8 group
of pixels.
- Frame header:
sample precision
(width, height) of image
number of components
unique ID (for each component)
horizontal/vertical sampling factors (for each component)
quantization table to use (for each component)
- Scan header
Number of components in scan
component ID (for each component)
Huffman table for each component (for each component)
- Misc. (can occur between headers)
Quantization tables
Huffman Tables
Arithmetic Coding Tables
Comments
Application Data
Dave Marshall
10/4/2001