1、BS ISO/IEC 18477-2:2016 Information technology Scalable compression and coding of continuous-tone still images Part 2: Coding of high dynamic range images BSI Standards Publication WB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS ISO/IEC 18477-2:2016 BRITISH STANDARD National foreword This
2、 British Standard is the UK implementation of ISO/IEC 18477-2:2016. 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 t
3、o its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2016. Published by BSI Standards Limited 2016 ISBN 978 0 580 85938 0 ICS 35.040 Compliance with a British Sta
4、ndard cannot confer immunity from legal obligations. This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 August 2016. Amendments/corrigenda issued since publication Date T e x t a f f e c t e dBS ISO/IEC 18477-2:2016 Information technology Sca
5、lable compression and coding of continuous-tone still images Part 2: Coding of high dynamic range images Technologies de linformation Compression chelonnable et codage dimages plates en ton continu Partie 2: Codage dimages gamme dynamique leve INTERNATIONAL STANDARD ISO/IEC 18477-2 Reference number
6、ISO/IEC 18477-2:2016(E) First edition 2016-07-15 ISO/IEC 2016 BS ISO/IEC 18477-2:2016ii ISO/IEC 2016 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO/IEC 2016, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized othe
7、rwise in any form or 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
8、 Ch. de Blandonnet 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 18477-2:2016(E)BS ISO/IEC 18477-2:2016ISO/IEC 18477-2:2016(E)Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 1 4
9、 Abbreviated terms and symbols 4 4.1 Abbreviated terms . 4 4.2 Symbols . 4 5 Conventions . 4 5.1 Conformance language . 4 5.2 Operators . 4 5.2.1 Arithmetic operators 5 5.2.2 Logical operators . 5 5.2.3 Relational operators . 5 5.2.4 Precedence order of operators 5 5.2.5 Mathematical functions . 6 6
10、 General 6 6.1 Elements specified . 6 6.2 High level overview of this document . 6 6.3 High level functional overview of decoding process 7 6.4 Encoder requirements 8 6.5 Decoder requirements 8 7 Dec oder definition 8 7.1 Decoder functionality overview . 8 7.2 Legacy Inverse Decorrelation Block B3 .
11、 9 7.3 Base Mapping and Colour space conversion Block B4 10 7.4 Residual decode Blocks B5, B6 .11 7.5 Residual Mapping and Inverse Decorrelation Blocks B7, B8 .12 7.6 HDR Reconstruction Blocks B9, B10 .13 8 C odestr eam s yntax for Main Pr ofile 13 8.1 Main Profile Header Structure . .13 8.2 Paramet
12、er ASCII segment .14 8.3 Parameter binary segment 16 8.4 Residual codestream segment 16 Annex A (normative) Checksum computation 17 Bibliography .18 ISO/IEC 2016 All rights reserved iii Contents PageBS ISO/IEC 18477-2:2016ISO/IEC 18477-2:2016(E) Foreword ISO (the International Organization for Stand
13、ardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the development of International Standards through technical committees established by the respective organizat
14、ion to deal with particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information technology,
15、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 described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of docume
16、nt 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 the possibility that some of the elements of this document may be the subject of patent rights. ISO and IEC shall not be held res
17、ponsible 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 on the ISO list of patent declarations received (see www.iso.org/patents). Any trade name used in this document is information giv
18、en 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 conformit y assessment, as well as information about ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to
19、 Trade (TBT) see the following URL: www.iso.org/iso/foreword.html. The committee responsible for this document is ISO/IEC JTC 1, Information technology, SC 29, Coding of audio, picture, multimedia and hypermedia information. A list of all parts in the ISO 18477 series, published under the general ti
20、tle Information technology - Scalable compression and coding of continuous-tone still images, can be found on the ISO website.iv ISO/IEC 2016 All rights reservedBS ISO/IEC 18477-2:2016ISO/IEC 18477-2:2016(E) Introduction This document is an extension of ISO/IEC 18477-1, a compression system for cont
21、inuous tone digital still images which is backward compatible with Rec. ITU-T T.81 | ISO/IEC 10918-1. That is, legacy applications conforming to Rec. ITU-T T.81 | ISO/IEC 10918-1 will be able to reconstruct streams generated by an encoder conforming to this document, but will possibly not be able to
22、 reconstruct such streams in full dynamic range, full quality or other features defined in this document. The aim of this document is to provide a migration path for legacy applications to support coding of high-dynamic range images. Existing tools depending on the existing standards will continue t
23、o work, but will only be able to reconstruct a lossy and/or a low-dynamic range version of the image contained in the codestream. This document specifies a codestream, referred to as JPEG XT, which is designed primarily for storage and interchange of continuous-tone photographic content. This docume
24、nt specifies a coded codestream format for storage of continuous-tone high and low dynamic range photographic content. JPEG XT Part 2 is a scalable image coding system supporting multiple component images in floating point. It is by itself an extension of the coding tools defined in ISO/IEC 18477-1;
25、 the codestream is composed in such a way that legacy applications conforming to Rec. ITU-T T.81 | ISO/IEC 10918-1 are able to reconstruct a lower quality, low dynamic range, eight bits per sample version of the image. Today, the most widely used digital photography format, a minimal implementation
26、of JPEG (specified in Rec. ITU-T T.81 | ISO/IEC 10918-1), uses a bit depth of 8; each of the three channels that together compose an image pixel is represented by 8 bits, providing 256 representable values per channel. For more demanding applications, it is not uncommon to use a bit depth of 16 or h
27、igher, providing greater than 65 536 representable values to describe each channel within a pixel, resulting on over 2.8 10 14representable colour values. In some less common scenarios, even greater bit depths are used. The most common photo and image formats use an 8-bit or 16-bit unsigned integer
28、value to represent some function of the intensity of each colour channel. While it might be theoretically possible to agree on one method for assigning specific numerical values to real world colours, doing so is not practical. Since any specific device has its own limited range for colour reproduct
29、ion, the devices range may be a small portion of the agreed-upon universal colour range. As a result, such an approach is an extremely inefficient use of the available numerical values, especially when using only 8 bits (or 256 unique values) per channel. To represent pixel values as efficiently as
30、possible, devices use a numeric encoding optimized for their own range of possible colours or gamut. JPEG XT is primarily designed to provide coded data containing high dynamic range and wide colour gamut content while simultaneously providing 8 bits per pixel low dynamic range images using tools de
31、fined in ISO/IEC 18477-1. The goal is to provide a backward compatible coding specification that allows legacy applications and existing toolchains to continue to operate on codestreams conforming to this this document. JPEG XT has been designed to be backward compatible to legacy applications while
32、 at the same time having a small coding complexity; JPEG XT uses, whenever possible, functional blocks of Rec. ITU-T T.81 | ISO/IEC 10918-1 to extend the functionality of the legacy JPEG Coding System. It is optimized for storage and transmission of high dynamic range and wide colour gamut 32 bit fl
33、oat images while also enabling low-complexity encoder and decoder implementations. ISO/IEC 2016 All rights reserved vBS ISO/IEC 18477-2:2016BS ISO/IEC 18477-2:2016Information technology Scalable compression and coding of continuous-tone still images Part 2: Coding of high dynamic range images 1 Scop
34、e This document specifies a coding format, referred to as JPEG XT, which is designed primarily for continuous-tone photographic content. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this documen
35、t. For 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 Part
36、1 ISO/IEC 18477-1, Information technology Scalable Compression and Coding of Continuous-Tone Still Images, Core Coding System Specification IEC 61966-2-1, sRGB Colour management Default RGB colour space sRGB 3 T erms a nd definiti ons For the purposes of this document, the following terms and defini
37、tions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: IEC Electropedia: available at http:/ /www.electropedia.org/ ISO Online browsing platform: available at http:/ /www.iso.org/obp 3.1 ASCII encoding character encoding scheme defined by AN
38、SI X3.4-1986 3.2 codestream partially encoded or decoded sequence of bits comprising an entropy-coded segment 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 18477-2:2016(E) ISO/IEC 2016 All rights reserved 1BS ISO/IEC
39、 18477-2:2016ISO/IEC 18477-2:2016(E) 3.6 (coding) process general term for referring to an encoding process, a decoding process, or both 3.7 compression reduction in the number of bits used to represent source image data 3.8 component two-dimensional array of samples having the same designation in t
40、he output or display device Note 1 to entry: An image typically consists of several components, e.g. red, green and blue. 3.9 continuous-tone image image whose components have more than one bit per sample 3.10 discrete cosine transform DCT sum of cosine transforms at different frequencies 3.11 decod
41、er embodiment of a decoding process 3.12 decoding process process which takes as its input compressed image data and outputs a continuous-tone image 3.13 downsampling procedure by which the spatial resolution of a component is reduced 3.14 encoder embodiment of an encoding process 3.15 encoding proc
42、ess process which takes as its input a continuous-tone image and outputs compressed image data 3.16 grayscale image continuous-tone image that has only one component 3.17 high dynamic range image or image data comprised of more than eight bits per sample 3.18 Joint Photographic Experts Group JPEG in
43、formal name of the working group which created this part of ISO/IEC 18477 Note 1 to entry: The term “joint” comes from the ITU-T and ISO/IEC collaboration.2 ISO/IEC 2016 All rights reservedBS ISO/IEC 18477-2:2016ISO/IEC 18477-2:2016(E) 3.19 legacy decoder embodiment of a decoding process conforming
44、to Rec. ITU-T T.81 | ISO/IEC 10918-1, confined to the lossy discrete cosine transformation (DCT) process and the baseline, sequential or progressive modes, decoding at most four components to eight bits per component 3.20 lossless descriptive term for encoding and decoding processes and procedures i
45、n which the output of the decoding procedure(s) is identical to the input of the encoding procedure(s) 3.21 lossless coding mode of operation which refers to any one of the coding processes defined in this part of ISO/IEC 18477 in which all of the procedures are lossless 3.22 lossy descriptive term
46、for encoding and decoding processes which are not lossless 3.23 low-dynamic range image or image data comprised of data with no more than 8 bits per sample 3.24 marker two-byte code in which the first byte is hexadecimal FF and the second byte is a value between 1 and hexadecimal FE 3.25 marker segm
47、ent marker together with its associated set of parameters 3.26 minimum coded unit MCU smallest group of data units that is coded 3.27 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
48、its red, green and blue value. 3.28 precision number of bits allocated to a particular sample or discrete cosine transformation (DCT) coefficient 3.29 procedure set of steps which accomplishes one of the tasks which comprise an encoding or decoding process 3.30 residual codestream codestream that co
49、ntains an encoded (according to Rec. ITU-T T.81 | ISO/IEC 10918-1) residual image 3.31 residual data data that contains luminance ratio and red, green, and blue (RGB) differential data ISO/IEC 2016 All rights reserved 3BS ISO/IEC 18477-2:2016ISO/IEC 18477-2:2016(E) 3.32 residual image pseudo image that contains encoded luminance ratio as luminance and encoded chrominance data that is computed from red, green, and blue (RGB) differential data using Multiple Component Decorrelation
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