1 <?xml version="1.0" encoding="ISO-8859-1"?>
2 <!DOCTYPE quantization-tables [
3 <!ELEMENT quantization-tables (table)+>
4 <!ELEMENT table (description , levels)>
5 <!ELEMENT description (CDATA)>
6 <!ELEMENT levels (CDATA)>
7 <!ATTLIST table slot ID #REQUIRED>
8 <!ATTLIST levels width CDATA #REQUIRED>
9 <!ATTLIST levels height CDATA #REQUIRED>
10 <!ATTLIST levels divisor CDATA #REQUIRED>
13 JPEG quantization table created by Dr. Nicolas Robidoux, Senior Research
14 Scientist at Phase One (www.phaseone.com) for use with 2x2 Chroma
15 subsampling and (IJG-style, hence ImageMagick-style) quality level
18 It is based on the one recommended in
20 Relevance of human vision to JPEG-DCT compression by Stanley A. Klein,
21 Amnon D. Silverstein and Thom Carney. In Human Vision, Visual
22 Processing and Digital Display III, 1992.
24 for 1 minute per pixel viewing.
26 Specifying only one table in this xml file has two effects when used with
27 the ImageMagick option
29 -define jpeg:q-table=PATH/TO/THIS/FILE
31 1) This quantization table is automatically used for all three channels;
33 2) Only one copy is embedded in the JPG file, which saves a few bits
34 (only worthwhile for very small thumbnails).
37 <table slot="0" alias="luma">
38 <description>Luma Quantization Table</description>
39 <levels width="8" height="8" divisor="1">
40 16, 16, 16, 18, 25, 37, 56, 85,
41 16, 17, 20, 27, 34, 40, 53, 75,
42 16, 20, 24, 31, 43, 62, 91, 135,
43 18, 27, 31, 40, 53, 74, 106, 156,
44 25, 34, 43, 53, 69, 94, 131, 189,
45 37, 40, 62, 74, 94, 124, 169, 238,
46 56, 53, 91, 106, 131, 169, 226, 311,
47 85, 75, 135, 156, 189, 238, 311, 418
51 If you want to use a different quantization table for Chroma (say), just add
53 <table slot="1" alias="chroma">
54 <description>Chroma Quantization Table</description>
55 INSERT 64 POSITIVE INTEGERS HERE, COMMA-SEPARATED
59 here (but outside of these comments).
61 </quantization-tables>