1、BS ISO/IEC 18477-2:2016Information technology Scalable compression andcoding of continuous-tone stillimagesPart 2: Coding of high dynamic rangeimagesBSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS ISO/IEC 18477-2:2016 BRITISH STANDARDNational forewordThis British
2、Standard is the UK implementation of ISO/IEC18477-2:2016. The UK participation in its preparation was entrusted to TechnicalCommittee IST/37, Coding of picture, audio, multimedia andhypermedia information.A list of organizations represented on this committee can beobtained on request to its secretar
3、y.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2016.Published by BSI Standards Limited 2016ISBN 978 0 580 85938 0ICS 35.040Compliance with a British Standard cannot confer i
4、mmunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 August 2016.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e dBS ISO/IEC 18477-2:2016Information technology Scalable compression and codin
5、g of continuous-tone still images Part 2: Coding of high dynamic range imagesTechnologies de linformation Compression chelonnable et codage dimages plates en ton continu Partie 2: Codage dimages gamme dynamique leveINTERNATIONAL STANDARDISO/IEC18477-2Reference numberISO/IEC 18477-2:2016(E)First edit
6、ion2016-07-15 ISO/IEC 2016BS ISO/IEC 18477-2:2016ii ISO/IEC 2016 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO/IEC 2016, Published in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, ele
7、ctronic 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 officeCh. de Blandonnet 8 CP 401CH-1214 Verni
8、er, Geneva, SwitzerlandTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgISO/IEC 18477-2:2016(E)BS ISO/IEC 18477-2:2016ISO/IEC 18477-2:2016(E)Foreword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Abbreviated terms and symbols 44.1 Abbreviated term
9、s . 44.2 Symbols . 45 Conventions . 45.1 Conformance language . 45.2 Operators . 45.2.1 Arithmetic operators 55.2.2 Logical operators . 55.2.3 Relational operators . 55.2.4 Precedence order of operators 55.2.5 Mathematical functions . 66 General 66.1 Elements specified . 66.2 High level overview of
10、this document . 66.3 High level functional overview of decoding process 76.4 Encoder requirements 86.5 Decoder requirements 87 Decoder definition 87.1 Decoder functionality overview . 87.2 Legacy Inverse Decorrelation Block B3 . 97.3 Base Mapping and Colour space conversion Block B4 107.4 Residual d
11、ecode Blocks B5, B6 . 117.5 Residual Mapping and Inverse Decorrelation Blocks B7, B8 .127.6 HDR Reconstruction Blocks B9, B10 . 138 Codestream syntax for Main Profile 138.1 Main Profile Header Structure 138.2 Parameter ASCII segment . 148.3 Parameter binary segment 168.4 Residual codestream segment
12、16Annex A (normative) Checksum computation 17Bibliography .18 ISO/IEC 2016 All rights reserved iiiContents PageBS ISO/IEC 18477-2:2016ISO/IEC 18477-2:2016(E)ForewordISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized s
13、ystem 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 organization to deal with particular fields of technical activity. ISO and IEC technical committees
14、 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, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.The procedures use
15、d 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 document should be noted. This document was drafted in accordance with the editorial rules of the
16、 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 responsible for identifying any or all such patent rights. Details of any patent rights identi
17、fied 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 given for the convenience of users and does not constitute an endorsement.For an explanation o
18、n the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.The committee responsible f
19、or 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 title Information technology - Scalable compression and coding of continuous-tone still images, c
20、an be found on the ISO website.iv ISO/IEC 2016 All rights reservedBS ISO/IEC 18477-2:2016ISO/IEC 18477-2:2016(E)IntroductionThis document is an extension of ISO/IEC 18477-1, a compression system for continuous tone digital still images which is backward compatible with Rec. ITU-T T.81 | ISO/IEC 1091
21、8-1. 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 reconstruct such streams in full dynamic range, full quality or other features defined in this d
22、ocument.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 to work, but will only be able to reconstruct a lossy and/or a low-dynamic range version of the ima
23、ge 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 document specifies a coded codestream format for storage of continuous-tone high and low dynamic range ph
24、otographic 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; the codestream is composed in such a way that legacy applications conforming to Rec. ITU-T T.81 |
25、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 of JPEG (specified in Rec. ITU-T T.81 | ISO/IEC 10918-1), uses a bit depth of 8; each of the three c
26、hannels 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 higher, providing greater than 65 536 representable values to describe each channel within a pixel, r
27、esulting on over 2.8 1014representable 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 value to represent some function of the intensity of each colour channel. While it might be theoretica
28、lly 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 reproduction, the devices range may be a small portion of the agreed-upon universal colour range. As a result,
29、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 possible, devices use a numeric encoding optimized for their own range of possible colours or gamut.JP
30、EG 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 defined in ISO/IEC 18477-1. The goal is to provide a backward compatible coding specification that allows
31、 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 at the same time having a small coding complexity; JPEG XT uses, whenever possible, functional blocks o
32、f 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 float images while also enabling low-complexity encoder and decoder implementations. ISO/IEC 2016 All righ
33、ts 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 images1 ScopeThis document specifies a coding format, referred to as JPEG XT, which is designed primarily for continu
34、ous-tone photographic content.2 Normative referencesThe following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the r
35、eferenced document (including any amendments) applies.ISO/IEC 10918-1, Information technology Digital compression and coding of continuous-tone still images: Requirements and guidelines Part 1ISO/IEC 18477-1, Information technology Scalable Compression and Coding of Continuous-Tone Still Images, Cor
36、e Coding System SpecificationIEC 61966-2-1, sRGB Colour management Default RGB colour space sRGB3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.ISO and IEC maintain terminological databases for use in standardization at the following addresses: IEC
37、 Electropedia: available at http:/www.electropedia.org/ ISO Online browsing platform: available at http:/www.iso.org/obp3.1ASCII encodingcharacter encoding scheme defined by ANSI X3.4-19863.2codestreampartially encoded or decoded sequence of bits comprising an entropy-coded segment3.3bytegroup of 8
38、bits3.4coderembodiment of a coding process3.5codingencoding or decodingINTERNATIONAL STANDARD ISO/IEC 18477-2:2016(E) ISO/IEC 2016 All rights reserved 1BS ISO/IEC 18477-2:2016ISO/IEC 18477-2:2016(E)3.6(coding) processgeneral term for referring to an encoding process, a decoding process, or both3.7co
39、mpressionreduction in the number of bits used to represent source image data3.8componenttwo-dimensional array of samples having the same designation in the output or display deviceNote 1 to entry: An image typically consists of several components, e.g. red, green and blue.3.9continuous-tone imageima
40、ge whose components have more than one bit per sample3.10discrete cosine transformDCTsum of cosine transforms at different frequencies3.11decoderembodiment of a decoding process3.12decoding processprocess which takes as its input compressed image data and outputs a continuous-tone image3.13downsampl
41、ingprocedure by which the spatial resolution of a component is reduced3.14encoderembodiment of an encoding process3.15encoding processprocess which takes as its input a continuous-tone image and outputs compressed image data3.16grayscale imagecontinuous-tone image that has only one component3.17high
42、 dynamic rangeimage or image data comprised of more than eight bits per sample3.18Joint Photographic Experts GroupJPEGinformal name of the working group which created this part of ISO/IEC 18477Note 1 to entry: The term “joint” comes from the ITU-T and ISO/IEC collaboration.2 ISO/IEC 2016 All rights
43、reservedBS ISO/IEC 18477-2:2016ISO/IEC 18477-2:2016(E)3.19legacy decoderembodiment of a decoding process conforming 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 compon
44、ents to eight bits per component3.20losslessdescriptive term for encoding and decoding processes and procedures in which the output of the decoding procedure(s) is identical to the input of the encoding procedure(s)3.21lossless codingmode of operation which refers to any one of the coding processes
45、defined in this part of ISO/IEC 18477 in which all of the procedures are lossless3.22lossydescriptive term for encoding and decoding processes which are not lossless3.23low-dynamic rangeimage or image data comprised of data with no more than 8 bits per sample3.24markertwo-byte code in which the firs
46、t byte is hexadecimal FF and the second byte is a value between 1 and hexadecimal FE3.25marker segmentmarker together with its associated set of parameters3.26minimum coded unitMCUsmallest group of data units that is coded3.27pixelcollection of sample values in the spatial image domain having all th
47、e same sample coordinatesNote 1 to entry: A pixel may consist of three samples describing its red, green and blue value.3.28precisionnumber of bits allocated to a particular sample or discrete cosine transformation (DCT) coefficient3.29procedureset of steps which accomplishes one of the tasks which
48、comprise an encoding or decoding process3.30residual codestreamcodestream that contains an encoded (according to Rec. ITU-T T.81 | ISO/IEC 10918-1) residual image3.31residual datadata that contains luminance ratio and red, green, and blue (RGB) differential data ISO/IEC 2016 All rights reserved 3BS
49、ISO/IEC 18477-2:2016ISO/IEC 18477-2:2016(E)3.32residual imagepseudo 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 Transformation defined in ISO/IEC 18477-13.33red, green, and blueRGBadditive colour model3.34luminance ratioarray of per pixel ratio of HDR image luminance and LDR image luminance3.35quantization valueinteger value used in the quantization procedure3.36quantizeact of
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