Movatterモバイル変換

Abstract

This specification defines a mechanism for storing images that use the Reference PQ EOTF specified in [BT2100-1] in the Portable Network Graphics (PNG) format (specified in [PNG]), without modification to existing chunks or the introduction of new chunks.

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This specification is intended to be published as a Working Group Note.

This document was published by theTimed Text Working Group as a Working Group Note. Comments regarding this document are welcome. Please send them topublic-tt@w3.org (subscribe,archives) with[png-hdr-pq] at the start of your email's subject.

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This document was produced by a group operating under the5 February 2004W3C Patent Policy.W3C maintains apublic list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes containsEssential Claim(s) must disclose the information in accordance withsection 6 of theW3C Patent Policy.

This document is governed by the1 March 2017W3C Process Document.

1.Introduction

This section is non-normative.

ThegAMA chunk of the Portable Network Graphics (PNG) format (specified in [PNG]) parameterizes the transfer function of the image as a power law. As such, it cannot model the Reference PQ EOTF specified in [BT2100-1], which is commonly used for HDR images.

This specification uses the existingiCCP chunk to unambiguously signal the color system of an image that uses the Reference PQ EOTF specified in [BT2100-1]. It also allows graceful processing by decoders that do not conform to this specification by recommending fallback values for thegAMA chunk,cHRM chunk, and embedded ICC profile.

2.PQ HDR PNG File

The fileSHALL conform to [PNG].

The image typeSHALL betruecolor.

The imageSHALL conform to one of the Pixel Encoding Systems specified in the table below.

The fileSHALL contain aniCCP chunk, constrained as follows:

• the profile name of theiCCP chunkSHALL be set as specified by the table below according to the Pixel Encoding System of the image; and
• the embedded ICC profile of theiCCP chunkSHOULD contained one of the ICC profiles specified by the table below according to the Pixel Encoding System of the image; and
• if present, the embedded ICC profileSHALL be compressed using Method 0, as specified in [PNG].

ThecHRM chunk and thegAMA chunk of the fileSHOULD be set as specified by the table below according to the Pixel Encoding System of the image.

3.Privacy and Security Considerations

This section is non-normative.

A.References