|Extension TIFF Tag JPEGTables|
TIFF Tag Reference
TIFF Tag JPEGTables
JPEG quantization and/or Huffman tables.
This field is the only auxiliary TIFF field added for new-style JPEG compression (Compression=7). It is optional.
The purpose of JPEGTables is to predefine JPEG quantization and/or Huffman tables for subsequent use by JPEG image segments. When this is done, these rather bulky tables need not be duplicated in each segment, thus saving space and processing time. JPEGTables may be used even in a single-segment file, although there is no space savings in that case.
When the JPEGTables field is present, it shall contain a valid JPEG "abbreviated table specification" datastream.