ISO 18619:2015

SLOVENSKI STANDARD
SIST ISO 18619:2020
01-april-2020
Barvno upravljanje upodobitvenih tehnologij - Kompenzacija črne točke
Image technology colour management - Black point compensation
Gestion de couleur en technologie d'image - Compensation du point noir
Ta slovenski standard je istoveten z: ISO 18619:2015
ICS:
17.180.20 Barve in merjenje svetlobe Colours and measurement of
light
35.240.30 Uporabniške rešitve IT v IT applications in information,
informatiki, dokumentiranju in documentation and
založništvu publishing
37.100.99 Drugi standardi v zvezi z Other standards related to
grafično tehnologijo graphic technology
SIST ISO 18619:2020 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ISO 18619:2020

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SIST ISO 18619:2020
INTERNATIONAL ISO
STANDARD 18619
First edition
2015-07-01
Image technology colour
management — Black point
compensation
Gestion de couleur en technologie d’image — Compensation du point
noir
Reference number
ISO 18619:2015(E)
©
ISO 2015

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SIST ISO 18619:2020
ISO 18619:2015(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 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 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 ISO’s member body in the country of
the requester.
ISO copyright office
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Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2015 – All rights reserved

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ISO 18619:2015(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 2
4.1 Constraints . 2
4.2 Computation. 3
4.2.1 Outline . 3
4.2.2 Functions used . 3
4.2.3 Computing the SourceBlackPoint . 4
4.2.4 Computing the DestinationBlackPoint for ICC profiles that are not LUT-based . 4
4.2.5 Computing the DestinationBlackPoint for ICC profiles that are LUT-based . 5
4.2.6 Computing the mapping from SourceBlackPoint to DestinationBlackPoint .10
4.2.7 Applying the black point compensation in a colour conversion .11
Annex A (informative) Why black point compensation is neccessary .12
Bibliography .14
© ISO 2015 – All rights reserved iii

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ISO 18619:2015(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
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 ISO documents 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 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
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 on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s 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/TC 130, Graphic technology, in cooperation with the
International Color Consortium.
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Introduction
Black point compensation (BPC) is a technique used to address colour conversion problems caused by
differences between the darkest level of black achievable on one device and the darkest level of black
achievable on another. This procedure was first implemented in Adobe Photoshop in the late 1990s.
The International Color Consortium (ICC) and ISO Technical Committee 130 (Graphic technology) have
created this document to allow black point compensation to be used in a consistent manner across
applications.
The purpose of BPC is to adjust a colour transform between the colour spaces of source and destination
ICC profiles, so that it retains shadow details and utilizes available black levels. The procedure depends
only on the rendering intent(s) and the source and destination ICC profiles, not on any points in a
particular image. Therefore, the colour transform using specific source and destination ICC profiles and
rendering intent can be computed once, and then efficiently applied to many images which use the same
ICC profile colour transform pair and rendering intent.
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SIST ISO 18619:2020
INTERNATIONAL STANDARD ISO 18619:2015(E)
Image technology colour management — Black point
compensation
1 Scope
This International Standard specifies a procedure, including computation, by which a transform between
ICC profiles can be adjusted (compensated) to take into account differences between the dark end of the
source colour space and the dark end of the destination colour space. This is referred to as black point
compensation (BPC). The relative colorimetric encoding of ICC profile transforms already provides a
mechanism for such adjustment of the light (white) end of the tone scale.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 15076-1, Image technology colour management — Architecture, profile format and data structure —
Part 1: Based on ICC.1:2010
ICC.1:2001-04, File Format for Color Profiles
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 15076-1 and the following
apply.
3.1
DestinationBlackPoint
coordinate representing a dark neutral reproducible colour in the destination colour gamut
3.2
DestinationProfile
ICC profile, containing the transform from profile connection space to the destination device colour
space
3.3
SourceBlackPoint
coordinate representing a dark neutral colour in the source colour gamut
3.4
SourceProfile
ICC profile, containing the transform from the source device colour space to the profile connection space
3.5
RenderingIntent
rendering intent of the conversion from a source ICC profile’s colour space to a destination ICC profile’s
colour space
3.6
LabIdentityProfile
real or virtual ICC profile that contains a bi-directional (identity) transform between CIELAB and
PCSLAB
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3.7
black point compensation
BPC
computational procedure by which a transform between the colour spaces of ICC profiles can be adjusted
(compensated) to take into account differences between the dark end of the source colour space and the
dark end of the destination colour space
3.8
L, a, b
L*, a*, or b* component of the CIELAB colour space
3.9
output-capable CMYK profile
CMYK profile containing a transform from the ICC PCS encoding to the colour space encoding
3.10
transform
mathematical operations that define the change in representation of a colour between two colour spaces
3.11
gamut
range of colours that a given system is capable of reproducing
4 Requirements
4.1 Constraints
The black point compensation procedure defined in this International Specification shall take as its
inputs a destination ICC profile, a source ICC profile, and a rendering intent (in this International
Standard called DestinationProfile, SourceProfile and RenderingIntent respectively).
Applications that apply black point compensation shall support ICC profiles that conform to ISO 15076-1
and ICC profiles that conform to ICC.1:2001-04.
NOTE 1 This requirement ensures that processing applications will properly process all Version 2 and Version
4 ICC profiles.
NOTE 2 ISO 15076-1 provides a description of source and destination ICC profiles.
The rendering intent shall be one of: RelativeColorimetric; Perceptual; or Saturation. The rendering
intent used with DestinationProfile shall be the same as the rendering intent used with SourceProfile.
Black point compensation is not appropriate for the AbsoluteColorimetric rendering intent.
The versions of SourceProfile and DestinationProfile do not need to match.
SourceProfile and DestinationProfile types shall be Input, Display, Output, or ColorSpace. The types of
SourceProfile and DestinationProfile do not need to match.
DestinationProfile shall contain a transform from the ICC PCS encoding to the colour space encoding.
The data colour spaces of the SourceProfile and DestinationProfile shall be Gray, RGB, CMYK or CIELAB.
The data colour spaces of SourceProfile and DestinationProfile do not need to match.
NOTE 3 Some implementations of BPC extend to additional colour spaces or mixed rendering intents. The way
in which BPC operates in these cases is outside the scope of this International Standard.
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4.2 Computation
4.2.1 Outline
Black point compensation shall be performed according to the following procedure:
a) the SourceBlackPoint of SourceProfile shall be calculated as specified in 4.2.3;
b) the DestinationBlackPoint of DestinationProfile shall be calculated as specified in 4.2.4 and 4.2.5;
c) a mapping from SourceBlackPoint to DestinationBlackPoint shall be calculated as specified in 4.2.6;
d) the mapping shall be applied in a colour conversion as specified in 4.2.7.
4.2.2 Functions used
4.2.2.1 Colour transform with profiles
T shall denote a function to transform a point in the data colour space of Profile1 to a point in the device
colour space of Profile2, using a rendering intent, such that
y = T (x, Profile1, Profile2, Intent) (1)
where
x is a point in the data colour space of Profile1;
y is a point in the data colour space of Profile2;
Intent is the rendering intent.
4.2.2.2 Darkest colour of a profile
D shall denote a function to provide the darkest colour coordinate in the data colour space of Profile for
a rendering intent, such that
dc = D (Profile, Intent) (2)
where
dc is the darkest colour
Profile is the profile being evaluated,
Intent is the rendering inte
...