1、BSI Standards Publication BS ISO/IEC 18477-1:2015 Information technology Scalable compression and coding of continuous-tone still images Part 1: Scalable compression and coding of continuous-tone still imagesBS ISO/IEC 18477-1:2015 BRITISH STANDARD National foreword This British Standard is the UK i
2、mplementation of ISO/IEC 18477-1:2015. The UK participation in its preparation was entrusted to Technical Committee IST/37, Coding of picture, audio, multimedia and hypermedia information. A list of organizations represented on this committee can be obtained on request to its secretary. This publica
3、tion does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2015. Published by BSI Standards Limited 2015 ISBN 978 0 580 85832 1 ICS 35.040 Compliance with a British Standard cannot confer immunity
4、from legal obligations. This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 July 2015. Amendments issued since publication Date Text affectedBS ISO/IEC 18477-1:2015 Information technology Scalable compression and coding of continuous-tone stil
5、l images Part 1: Scalable compression and coding of continuous-tone still images Technologies de linformation Compression chelonnable et codage dimages plates en ton continu Partie 1: Codage des images gamme dynamique leve INTERNATIONAL STANDARD ISO/IEC 18477-1 Reference number ISO/IEC 18477-1:2015(
6、E) First edition 2015-06-15 ISO/IEC 2015 BS ISO/IEC 18477-1:2015ii ISO/IEC 2015 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO/IEC 2015, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or
7、by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Ch. de Blandonnet 8
8、CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 copyrightiso.org www.iso.org ISO/IEC 18477-1:2015(E)BS ISO/IEC 18477-1:2015ISO/IEC 18477-1:2015(E)Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 1 4 Symbols and abbrevia
9、ted terms . 4 4.1 Symbols . 4 4.2 Abbreviated terms . 4 5 Conventions . 4 5.1 Conformance language . 4 5.2 Operators . 4 5.2.1 Arithmetic operators 4 5.2.2 Assignment operators . 5 5.2.3 Precedence order of operators 5 5.2.4 Mathematical functions . 5 6 General 5 6.1 General definitions 5 6.2 Functi
10、onal overview on the decoding process 6 6.3 Encoder requirements 6 6.4 Decoder requirements 6 Annex A (normative) Component subsampling and expansion of subsampling 7 Annex B (normative) Codestream syntax 9 Annex C (normative) Multi-component decorrelation .16 Bibliography .18 ISO/IEC 2015 All right
11、s reserved iii Contents PageBS ISO/IEC 18477-1:2015ISO/IEC 18477-1:2015(E) Foreword ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of ISO or I
12、EC participate in the development of International Standards through technical committees established by the respective organization to deal with particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations, gov
13、ernmental and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1. The procedures used to develop this document and those intended for its further maintenance are de
14、scribed in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of document should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to
15、the possibility that some of the elements of this document may be the subject of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or o
16、n the ISO list of patent declarations received (see www.iso.org/patents). Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement. For an explanation on the meaning of ISO specific terms and expressions related to conformity asses
17、sment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information The committee responsible for this document is ISO/IEC JTC 1, Information technology, SC 29, Coding of audio, picture, multime
18、dia and hypermedia information. ISO/IEC 18477 consists of the following parts, under the general title: JPEG HDR image coding system: Part 1: Coding of high dynamic range images Part 2: Extensions for high dynamic range images Part 3: Box file format Part 6: IDR Integer Coding Part 7: HDR Floating-P
19、oint Coding The following parts are under preparation: Part 4: Conformance testing Part 5: Reference software Part 8: Coding of high dynamic range images Part 9: Encoding of alpha channelsiv ISO/IEC 2015 All rights reservedBS ISO/IEC 18477-1:2015ISO/IEC 18477-1:2015(E) Introduction This part of ISO/
20、IEC 18477 specifies a coded codestream format for storage of continuous-tone photographic content. JPEG XT is a scalable image coding system that builds on top of the legacy Rec. ITU-T T.81 | ISO/IEC 10918-1 coding system, also known as JPEG, but extends it in a backwards compatible way. This part o
21、f ISO/IEC 18477 specifies the commonly deployed components of the JPEG coding system. Additional parts of ISO/IEC 18477 will extend on this baseline. JPEG XT has been designed to be backwards compatible to legacy applications while at the same time having a small coding complexity; JPEG XT uses, whe
22、never possible, functional blocks of Rec. ITU-T T.81 | ISO/IEC 10918-1, Rec. ITU-T T.86 | ISO/IEC 10918-4 and Rec. ITU-T T.871 | ISO/IEC 10918-5 to extend the functionality of the legacy JPEG Coding System. It is optimized for good image quality and compression efficiency while also enabling low-com
23、plexity encoding and decoding implementations. ISO/IEC 2015 All rights reserved vBS ISO/IEC 18477-1:2015BS ISO/IEC 18477-1:2015Information technology Scalable compression and coding of continuous-tone still images Part 1: Scalable compression and coding of continuous-tone still images 1 Scope This p
24、art of ISO/IEC 18477 specifies a coding format, referred to as JPEG XT, which is designed primarily for continuous-tone photographic content. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. Fo
25、r dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO/IEC 10918-1, Information technology Digital compression and coding of continuous-tone still images Requirements and guidelines ISO/IEC 109
26、18-4, Information technology Digital compression and coding of continuous-tone still images: Registration of JPEG profiles, SPIFF profiles, SPIFF tags, SPIFF colour spaces, APPn markers, SPIFF compression types, and Registration Authorities (REGAUT) ISO/IEC 10918-5, Information technology Digital co
27、mpression and coding of continuous-tone still images: JPEG File Interchange Format (JFIF) 3 T erms a nd definiti ons For the purposes of this document, the following definitions apply. 3.1 bit stream partially encoded or decoded sequence of bits comprising an entropy-coded segment 3.2 block 8 8 arra
28、y of samples or an 8 8 array of DCT coefficient values of one component 3.3 byte group of 8 bits 3.4 coder embodiment of a coding process 3.5 coding encoding or decoding INTERNATIONAL ST ANDARD ISO/IEC 18477-1:2015(E) ISO/IEC 2015 All rights reserved 1BS ISO/IEC 18477-1:2015ISO/IEC 18477-1:2015(E) 3
29、.6 compression reduction in the number of bits used to represent source image data 3.7 component two-dimensional array of samples having the same designation in the output or display device Note 1 to entry: An image typically consists of several components, e.g. red, green and blue. 3.8 continuous-t
30、one image image whose components have more than one bit per sample 3.9 discrete cosine transform DCT either the forward discrete cosine transform or the inverse discrete cosine transform 3.10 downsampling procedure by which the spatial resolution of a component is reduced 3.11 entropy-coded (data) s
31、egment independently decodable sequence of entropy encoded bytes of compressed image data 3.12 entropy decoder embodiment of an entropy decoding procedure 3.13 entropy decoding lossless procedure which recovers the sequence of symbols from the sequence of bits produced by the entropy encoder 3.14 en
32、tropy encoder embodiment of an entropy encoding procedure 3.15 entropy encoding lossless procedure which converts a sequence of input symbols into a sequence of bits such that the average number of bits per symbol approaches the entropy of the input symbols 3.16 grayscale image continuous-tone image
33、 that has only one component 3.17 joint photographic experts group JPEG informal name of the committee which created this International Standard Note 1 to entry: The “joint” comes from the ITU-T and ISO/IEC collaboration. 3.18 legacy decoder embodiment of a decoding process conforming to Rec. ITU- T
34、 T.81 | ISO/IEC 10918- 1 operating in baseline, sequential or progressive mode with a sample resolution of eight bits2 ISO/IEC 2015 All rights reservedBS ISO/IEC 18477-1:2015ISO/IEC 18477-1:2015(E) 3.19 marker two-byte code in which the first byte is hexadecimal FF and the second byte is a value bet
35、ween 1 and hexadecimal FE 3.20 marker segment marker and associated set of parameters 3.21 pixel collection of sample values in the spatial image domain having all the same sample coordinates Note 1 to entry: A pixel may consist of three samples describing its red, green and blue value. 3.22 precisi
36、on number of bits allocated to a particular sample or DCT coefficient 3.23 procedure set of steps which accomplishes one of the tasks which comprise an encoding or decoding process 3.24 quantization value integer value used in the quantization procedure 3.25 quantize act of performing the quantizati
37、on procedure for a DCT coefficient 3.26 sample one element in the two-dimensional array which comprises a component 3.27 sample grid common coordinate system for all samples of an image with the samples at the top left edge of the image having the coordinates (0, 0), the first coordinate increases t
38、owards the right, the second to the bottom 3.28 scan single pass through the data for one or more of the components in an image 3.29 scan header marker segment that contains a start-of-scan marker and associated scan parameters that are coded at the beginning of a scan 3.30 upsampling procedure by w
39、hich the spatial resolution of a component is increased 3.31 vertical sampling factor relative number of vertical data units of a particular component with respect to the number of vertical data units in the other components in the frame ISO/IEC 2015 All rights reserved 3BS ISO/IEC 18477-1:2015ISO/I
40、EC 18477-1:2015(E) 4 Symbols and abbreviated terms 4.1 Symbols X width of the sample grid in positions Y height of the sample grid in positions Nf number of components in an image s i, x subsampling factor of component i in horizontal direction s i, y subsampling factor of component i in vertical di
41、rection H i subsampling indicator of component i in the frame header V i subsampling indicator of component i in the frame header v x, y sample value at the sample grid position x, y 4.2 Abbreviated terms ASCII American Standard Code for Information Interchange DC Lowpass AC Highpass LSB Least Signi
42、ficant Bit MSB Most Significant Bit DCT Discrete Cosine Transformation 5 Conventions 5.1 Conformance language The keyword “reserved” indicates a provision that is not specified at this time, shall not be used, and may be specified in the future. The keyword “forbidden” indicates “reserved” and in ad
43、dition indicates that the provision will never be specified in the future. 5.2 Operators NOTE Many of the operators used in this part of ISO/IEC 18477 are similar to those used in the C programming language. 5.2.1 Arithmetic operators + Addition Subtraction (as a binary operator) or negation (as a u
44、nary prefix operator) Multiplication / Division without truncation or rounding4 ISO/IEC 2015 All rights reservedBS ISO/IEC 18477-1:2015ISO/IEC 18477-1:2015(E) 5.2.2 Assignment operators = Assignment operator 5.2.3 Precedence order of operators Operators are listed below in descending order of preced
45、ence. If several operators appear in the same line, they have equal precedence. When several operators of equal precedence appear at the same level in an expression, evaluation proceeds according to the associativity of the operator either from right to left or from left to right. Operators Type of
46、operation Associativity (), , . Expression Left to Right Unary negation , / Multiplication Left to Right +, Addition and Subtraction Left to Right , = Relational Left to Right 5.2.4 Mathematical functions x Ceiling of x. Returns the smallest integer that is greater than or equal to x. x Floor of x.
47、Returns the largest integer that is lesser than or equal to x. |x| Absolute value, is x for x max or otherwise x. 6 General 6.1 Gener al definition s The purpose of this clause is to give an informative overview of the elements specified in this part of ISO/IEC 18477. Another purpose is to introduce
48、 many of the terms which are defined in Clause 3. These terms are printed in italics upon first usage in this clause. There are three elements specified in this part of ISO/IEC 18477: a) An encoder is an embodiment of an encoding process. An encoder takes as input digital source image data and encod
49、er specifications, and by means of a specified set of procedures generates as output a codestream. b) A decoder is an embodiment of a decoding process. A decoder takes as input a codestream, and by means of a specified set of procedures generates as output digital reconstructed image data. c) The codestream is a compressed image data representation which includes all necessary data to allow a (full or approximate) reconstruction of the sample val
