SIST ISO 12640-3:2022

INTERNATIONAL ISO
STANDARD 12640-3
Second edition
2022-08
Graphic technology — Prepress digital
data exchange —
Part 3:
CIELAB standard colour image data
(CIELAB/SCID)
Technologie graphique — Échange de données numériques de
préimpression —
Partie 3: Données d'images en couleur normalisées CIELAB (CIELAB/
SCID)
Reference number
ISO 12640-3:2022(E)
© ISO 2022

---------------------- Page: 1 ----------------------
ISO 12640-3:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
  © ISO 2022 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 12640-3:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 2
5 Data description and definition . .3
5.1 Data set definition . 3
5.2 Colour encoding used in this document . 3
5.2.1 Image data encoding . 3
5.2.2 Image data arrangement . 3
5.2.3 CIELAB image data (16 bits per channel) . 3
5.2.4 CIELAB image data (8 bits per channel) . 4
5.3 Natural images. 4
5.4 Synthetic images . 7
5.4.1 Colour charts . 7
5.4.2 Vignettes . 9
5.4.3 Synthetic image format . 10
6 Electronic data .11
6.1 Image file characteristics . 11
6.2 Image file formats . 11
Annex A (normative) Guidance for use of digital data .12
Annex B (informative) Definition of the reference colour gamut .14
Annex C (normative) Checksum data .21
Annex D (informative) Typical TIFF file headers used for image data .22
Annex E (informative) Text insertion .24
Annex F (informative) Histogram and gamut plots .25
Annex G (informative) CIELAB values in colour charts .29
Bibliography .34
iii
© ISO 2022 – All rights reserved

---------------------- Page: 3 ----------------------
ISO 12640-3:2022(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 of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/
iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 130, Graphic technology.
This second edition cancels and replaces the first edition (ISO 12640-3:2007), of which it constitutes a
minor revision. The changes are as follows:
— CIE Publication 15:2004 has been changed to CIE Publication 15 Colorimetry;
— in 3.4, the definition of colour space has been updated based on revision to CIE Publication 17 in
2020;
— in the Bibliography, CIE S 17:2020 ILV has been updated to International lighting vocabulary, 2nd
edition.
A list of all parts in the ISO 12640 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
  © ISO 2022 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 12640-3:2022(E)
Introduction
0.1  Need for standard digital test images
Standard test images provide a set of data that can be used for any of the following tasks:
— evaluating the colour reproduction of imaging systems;
— evaluating colour image output devices;
— evaluating the effect of image processing algorithms applied to the images;
— evaluating the coding technologies necessary for the storage and transmission of high-definition
image data.
Because they exist as standard, well-defined, high-quality image data sets, typical of the range of image
content commonly encountered, they enable users to be confident that the images will produce good
quality reproductions, if properly rendered, and that they provide a reasonable test of the evaluation
task being undertaken. No limited set of images can fully test any system, but the sets provided give
as reasonable a test as can be expected from a limited image set. Furthermore, the existence of a
standard image data set enables users in different locations to produce comparisons without the need
to exchange images prior to reproduction.
However, different applications require that the standard image data be provided in different image
states using different image encodings (see ISO 22028-1). The user needs to select those appropriate to
the evaluation task being undertaken. Whilst transformation of the image data to another image state
is always possible, there is, in general, no agreement amongst experts as to how this is best done. Thus,
it has been considered preferable to provide data in three different image states in the various parts of
ISO 12640.
ISO 12640-1 provides a set of 8-bits-per-channel data that is defined in terms of CMYK dot percentages.
The colours resulting from reproduction of CMYK data are strictly defined only at the time of printing
and, as such, the data are only applicable to evaluation of CMYK printing applications. Transformations
to other image states and colour encodings are not necessarily well defined. In fact, the data might not
even be useful for CMYK printing processes different from those typically found in traditional graphic
arts applications as the image data are defined to produce “pleasing” images when reproduced on
systems using “typical” inks and producing “typical” tone value rendering. Printing systems that use
inks of a distinctly different colour, or produce a very different tone value rendering, will not reproduce
them as pleasing images without a well-defined colour transformation. Moreover, with a bit depth of
only 8 bits per channel, any colour transformation employed will probably introduce artefacts.
ISO 12640-2 provides a set of test image data encoded both as XYZ tristimulus values with a depth of
16 bits per channel and as sRGB (defined in IEC 61966-2-1) with a bit depth of 8 bits per channel. (The
higher bit depth for the XYZ encoding is necessary because of the perceptual non-uniformity of the
XYZ colour space.) Both sets of data are optimized for viewing on a reference sRGB CRT display in the
reference sRGB viewing environment, and relative to CIE standard illuminant D65 for which the XYZ
values were computed. The images are mainly designed to be used on systems utilizing sRGB as the
reference encoding, and as such are mainly applicable to the consumer market and those systems for
which the colour monitor is the “hub” device. Although such systems are used for some applications
in the graphic arts industry, sRGB is by no means the most common image encoding. Furthermore, a
particular drawback is the fact that the sRGB colour gamut is quite different in shape than the colour
gamut of typical offset printing. This difference can necessitate fairly aggressive colour re-rendering to
produce optimal prints from sRGB image data.
In order to be useful for applications where large, print-referred output gamuts are encountered,
common in graphic technology and photography, it was felt that it would be desirable to produce an
image set in which some colours are permitted to be encoded close to the boundary of the full colour
gamut attainable with surface colours. Furthermore, from the perspective of colour management it
is advantageous if the images are referenced to illuminant D50, which is the predominant reference
v
© ISO 2022 – All rights reserved

---------------------- Page: 5 ----------------------
ISO 12640-3:2022(E)
illuminant used in graphic arts and photography, both for viewing and measurement. For this reason it
has also become the predominant reference illuminant for most colour management applications.
The purpose of this document is, therefore, to provide a test image data set with a large colour gamut
related to illuminant D50. The bit depth of the natural images is 16 bits per channel, while the colour
charts and vignettes are 8 bits per channel.
0.2 Definition of the reference colour gamut
The reference colour gamut defined for this document originated from three quite separate sources.
However, it was noted that there was considerable similarity between the three. One definition came
from work within ISO/TC 130 itself, and this arose by consideration of various sets of published data,
which together were taken to define the colour gamut of surface colours. The other definitions arose
from work within Hewlett-Packard, which was focused on the colour gamut obtainable by printing, and
that of a group of German photographic printing experts. The similarity of these led to the conclusion
that it is desirable to reconcile them into a single gamut that would be taken as the reference colour
gamut for this document. Full details of the reference colour gamut and its derivation are given in
Annex B.
0.3  Characteristics of the test images
The performance of any colour reproduction system is normally evaluated both subjectively (by
viewing the final output image) and objectively (by measurement of control elements). This requirement
dictated that the test images include both natural scenes (pictures) and synthetic images (colour charts
and colour vignettes). Because the results of subjective image evaluation are strongly affected by the
image content, it was important to ensure that the natural images were of high quality and contained
diverse subject matter. However, by requiring images to look natural, it is difficult within a single,
relatively small sample set to produce elements in the scene that contain the subtle colour differences
required in such test images and that cover the full reference colour gamut defined. It is also important
to have some images that contain subtle differences in near-neutral colours. Thus, while most images
contain colours that extend to the gamut boundary, this is often only for a limited range of hues in each
image. The full reference colour gamut can only be explored by utilizing the synthetic colour chart.
A survey was conducted of all ISO/TC 130 member countries to identify desirable image content and
to solicit submission of suitable images for consideration. The image set that resulted consists of eight
natural images, eight colour charts and two colour vignettes. The natural images include flesh tones,
images with detail in the extreme highlights or shadows, neutral colours, brown and wood-tone colours
that are often difficult to reproduce, memory colours, complicated geometric shapes, fine detail, and
highlight and shadow vignettes. The colour charts and colour vignettes show the reference colour
gamut (in CIE Lab colour space) in cross-sections for 16 and 8 hue angles, respectively.
0.4  File format of the digital test images
* * *
All of the images consist of pixel interleaved data (L then a then b ) with the data origin at the upper
left of the image, as viewed naturally, and organized by rows. These data are available as individual
files, which are a normative part of this part of this document. The image file format is as specified
in ISO 12639:2004, Annex H, with BitsPerSample set to 16, 16, 16. The images can be imported and
manipulated as necessary by a wide variety of imaging software tools and platforms commonly in
general use in the industry. See Annex D for details of the TIFF header.
1)
All colour charts and vignettes consist of files in Adobe® PDF format.
1) This information is given for the convenience of users of this document and does not constitute an endorsement
by ISO of the product named.
vi
  © ISO 2022 – All rights reserved

---------------------- Page: 6 ----------------------
INTERNATIONAL STANDARD ISO 12640-3:2022(E)
Graphic technology — Prepress digital data exchange —
Part 3:
CIELAB standard colour image data (CIELAB/SCID)
1 Scope
This document specifies a set of standard large gamut colour images (encoded as 16-bit CIELAB digital
data) that can be used for the evaluation of changes in image quality during coding, image processing
(including transformation, compression and decompression), displaying on a colour monitor and
printing. These images can be used for research, testing and assessing of output systems such as
printers, colour management systems and colour profiles.
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 document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 12639:2004, Graphic technology — Prepress digital data exchange — Tag image file format for image
technology (TIFF/IT)
ISO 13655, Graphic technology — Spectral measurement and colorimetric computation for graphic arts
images
ISO 22028-1, Photography and graphic technology — Extended colour encodings for digital image storage,
manipulation and interchange — Part 1: Architecture and requirements
PDF Reference: Adobe Portable Document Format, Version 1.4 3rd edition., Adobe Systems Incorporated,
(ISBN 0-201-75839-3)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
checksum
sum of the digits in a file that can be used to check if a file has been transferred properly
Note 1 to entry: Often, only the least significant bits are summed.
3.2
colour gamut
solid in a colour space, consisting of all those colours that are present in a specific scene, artwork,
photograph, photomechanical or other reproduction; or are capable of being created using a particular
output device and/or medium
[SOURCE: ISO 12640-4:2011]
1
© ISO 2022 – All rights reserved

---------------------- Page: 7 ----------------------
ISO 12640-3:2022(E)
3.3
colour sequence
order in which the colours are stored in a data file
3.4
colour space
geometric representation of colour in space
Note 1 to entry: A colour space is usually of three dimensions
Note 2 to entry: This entry was numbered 845-03-25 in IEC 60050-45:1987
[SOURCE: CIE S 17:2020 ILV: International Lighting Vocabulary, 2nd edition, modified]
3.5
colour value
numeric values associated with each of the pixels
3.6
data range
range of integers for a given variable in between a minimal and maximal value
3.7
global colour change
change to the colours in an image (often selectively by colour region) applied consistently to all parts of
the image
Note 1 to entry: This is in contrast to a local colour change where selected spatial areas of an image are changed
separately from the rest of the image area.
3.8
orientation
specifies the origin and direction of the first line of data with respect to the image content as viewed by
the end user
Note 1 to entry: The codes used to specify orientation are contained in ISO 12639.
3.9
pixel
smallest discrete picture element in a digital image file
3.10
pixel interleaving
* * *
colour data organized such that the L , a and b colour space values for one pixel are followed by the
same sequence of colour values for the next pixel; the specific order of colour components is determined
by the ColorSequence tag as defined in ISO 12639
Note 1 to entry: Other forms of colour data interleaving are line and plane.
4 Requirements
This document consists of the images contained in the 18 image data files which are part of this
document. Their file names are listed in Table 4. The image characteristics of these data are described
in Clause 5 and the electronic data structure in Clause 6.
2
  © ISO 2022 – All rights reserved

---------------------- Page: 8 ----------------------
ISO 12640-3:2022(E)
5 Data description and definition
5.1 Data set definition
The set of standard colour image data consists of eight natural (photographed) images and ten synthetic
images created digitally on a computer. The synthetic images consist of eight colour charts consisting
of various patches, each 10 mm square, and two colour vignettes. The natural images are identified as
N1 to N8, and each of them also has a descriptive name derived from the picture content (e.g. bride and
groom). The synthetic images are identified as CC1 to CC8, CV1 and CV2.
The images are identified by the designation CIELAB/SCID. The co-ordinates of the text insertion are
provided in Annex E.
NOTE The image set defined in this document is based on the large gamut defined in Annex B. Image sets
contained in other document are based on different gamuts and can be more suitable for use in evaluation of
other applications.
5.2 Colour encoding used in this document
5.2.1 Image data encoding
The image data encoding shall be in accordance with the requirements of ISO 22028-1.
[10]
The image data are the desired CIELAB colorimetry defined by CIE Publication 15 , and measured in
accordance with ISO 13655, of reproductions of the images on the reference medium, with the reference
medium white point selected as the colour space white point. The image data are output-referred,
[11]
having been rendered to the reference medium of the ICC.1:2004-04 perceptual rendering intent,
which is defined as a hypothetical print on a substrate specified to have a neutral reflectance of 89 %
(the reference medium white point) and the darkest printable colour on this medium is assumed to have
a neutral reflectance of 0,347 31 % of the substrate reflectance (the reference medium black point). The
rendering target colour gamut for the reference medium is specified in Annex B. The reference viewing
environment is based on standard viewing condition P2, as specified for graphic arts and photography
in ISO 3664, but extended in the following way: the surfaces immediately surrounding the image are
assumed to be a uniform matt grey with a reflectance of 20 %. The reference viewing environment is
also assumed to have a viewing flare of 0,75 % of the luminance of the reference white. The CIELAB
image data are encoded as specified in 5.2.3 and 5.2.4.
5.2.2 Image data arrangement
* * *
The image data are pixel-interleaved in the colour sequence of L then a then b (16 bits) for the natural
* * *
images and L then a then b (8 bits) for the colour charts and the vignettes. The arrangement of data
follows the scanning of each image from the upper left corner to the upper right, then moving to the
next lower horizontal line. The resolution is 12 pixels/mm for every natural image.
5.2.3 CIELAB image data (16 bits per channel)
The CIELAB data for the natural images are encoded as 16-bit integers per channel, derived by
* * *
multiplying the L , a and b values for each pixel with the corresponding value for the data range.
*
 
L
*
L =×round 65535
 
16bit
 
100
 
* *
aa=×round()256 (1)
16bit
* *
b =×round()256 b
16biit
* * * * * *
where L , a and b represent normalised 16-bit values of L , a and b .
16bit 16bit 16bit
3
© ISO 2022 – All rights reserved

---------------------- Page: 9 ----------------------
ISO 12640-3:2022(E)
The data range of the values is:
* * *
L ∈{0.100}, a ∈{−128.+127} and b ∈{−128.+127},
* * * * *
L ∈{0.65 535}, a ∈{−32 768.+32 512} and b ∈{−32 768.+32 512}, a and b are
16bit 16bit 16bit 16bit 16bit
signed integers.
NOTE −32 678 = −128 × 256, and 32 512 = 127 × 256.
5.2.4 CIELAB image data (8 bits per channel)
The CIELAB data for the colour charts are encoded as 8-bit integers per channel, derived by multiplying
* * *
the L , a and b values for each pixel with the corresponding value for the data range.
*
 
L
*
L =×round 255
 
8bit
 
100
 
* *
aa=round() (2)
8bit
* *
b =round(bb )
8bit
* * * * * *
where L , a and b represent normalised 8 bit values of L , a and b .
8bit 8bit 8bit
The data range of the values is:
* * *
L ∈{0.100}, a ∈{−128.+127} and b ∈{−128.+127},
* * * * *
L ∈{0.255}, a ∈{−128.+127} and b ∈{−128.+127}, the a and b are signed integers.
8bit 8bit 8bit 8bit 8bit
5.3 Natural images
The characteristics of the eight natural images, shown in Figure 1, are given in Table 1.
Table 1 — Characteristics for natural images
Parameter Characteristics
Resolution 12 pixels/mm
* * *
Colour values 16 bits/channel L , a and b , with respect to illuminant D50 (defined as
* * *
media-relative, i.e. such that a white in the image has the L , a and b
values of 100, 0, 0)
File format ISO 12639:2004, Annex H, with BitsPerSample set to 16, 16, 16
This format also readable with TIFF 6.0 with extension, photometric
interpretation tag 8, CIELAB, signed encoding.
Label on image CIELAB/SCID
Image data orientation Horizontal scanning starting from top left and ending at bottom right
NOTE The natural images have been colour-rendered to produce the desired image colorimetry on the
reference print medium as described in Annex B. For the most part, the image colours will be within the reference
colour gamut. However, it is possible for some image colours to be slightly outside (this is somewhat dependent
on how the convex hull of the gamut is constructed). It is sometimes necessary to gamut map the results of colour
rendering and re-rendering processing to exactly fit the destination device colour gamut.
The description and typical usage of the natural images are given in Table 2. The descriptive names
of these images are given following the identification code. Figure 1 shows reduced size sRGB
reproductions of the natural images. Statistical and gamut data for each of the natural images are
* * *
shown in Annex F, as histograms of the L values and a versus b plots for each image, respectively.
4
  © ISO 2022 – All rights reserved

---------------------- Page: 10 ----------------------
ISO 12640-3:2022(E)
Table 2 — Natural images
Name Aspect, image Description and typical usage
size
N1 Bride and groom Horizontal, Image of a bride wearing white clothes and groom wearing black
2 560 × 2 048 clothes. Used to evaluate the rendering of human skin tones and neu-
pixels tral colours, especially highlights and shadows.
N2 People Horizontal, Image consisting of five people wearing colourful clothes, sitting on a
2 560 × 2 048 dark leather couch. Used to evaluate the colour rendering of extreme-
pixels ly colourful objects in the presence of skin tones and neutrals.
N3 Cashew nuts Vertical, Image of dried fruits and filled containers used to evaluate tonal
2 048 × 2 560 and colour rendering, in particular adjustments for grey component
pixels replacement.
N4 Meal Horizontal, Image with widely recognizable cooked food and pastel colours. Used
2 560 × 2 048 to evaluate high-key tonal rendering and food memory colours.
pixels
N5 Mandolin Vertical, Image of goods, including metallic objects, used to evaluate the
2 048 × 2 560 reproduction of colours, as well as the reproduction of the lustrous
pixels appearances of metallic objects.
N6 Tailor scene Horizontal, Still-life image of textile used to evaluate the tone reproduction in a
2 560 × 2 048 range of neutrals and textile structures (object moiré).
pixels
N7 Wool Horizontal, Image of different coloured balls of wool used to evaluate the repro-
2 560 × 2 048 duction of details in highly chr
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 12640-3
ISO/TC 130
Graphic technology — Prepress digital
Secretariat: SAC
data exchange —
Voting begins on:
2022-05-16
Part 3:
Voting terminates on:
CIELAB standard colour image data
2022-07-11
(CIELAB/SCID)
Technologie graphique — Échange de données numériques de
préimpression —
Partie 3: Données d'images en couleur normalisées CIELAB (CIELAB/
SCID)
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 12640-3:2022(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © ISO 2022

---------------------- Page: 1 ----------------------
ISO/FDIS 12640-3:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
  © ISO 2022 – All rights reserved

---------------------- Page: 2 ----------------------
ISO/FDIS 12640-3:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 2
5 Data description and definition . .3
5.1 Data set definition . 3
5.2 Colour encoding used in this document . 3
5.2.1 Image data encoding . 3
5.2.2 Image data arrangement . 3
5.2.3 CIELAB image data (16 bits per channel) . 3
5.2.4 CIELAB image data (8 bits per channel) . 4
5.3 Natural images. 4
5.4 Synthetic images . 7
5.4.1 Colour charts . 7
5.4.2 Vignettes . 9
5.4.3 Synthetic image format . 10
6 Electronic data .11
6.1 Image file characteristics . 11
6.2 Image file formats . 11
Annex A (normative) Guidance for use of digital data .12
Annex B (informative) Definition of the reference colour gamut .14
Annex C (normative) Checksum data .21
Annex D (informative) Typical TIFF file headers used for image data .22
Annex E (informative) Text insertion .24
Annex F (informative) Histogram and gamut plots .25
Annex G (informative) CIELAB values in colour charts .29
Bibliography .34
iii
© ISO 2022 – All rights reserved

---------------------- Page: 3 ----------------------
ISO/FDIS 12640-3:2022(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 of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 130, Graphic technology.
This second edition cancels and replaces the first edition (ISO 12640-3:2007), of which it constitutes a
minor revision. The changes are as follows:
— CIE Publication 15:2004 has been changed to CIE Publication 15 Colorimetry;
— in 3.4, the definition of colour space has been updated based on revision to CIE Publication 17 in
2020;
— in the Bibliography, CIE S 17:2020 ILV has been updated to International lighting vocabulary, 2nd
edition.
A list of all parts in the ISO 12640 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
  © ISO 2022 – All rights reserved

---------------------- Page: 4 ----------------------
ISO/FDIS 12640-3:2022(E)
Introduction
0.1  Need for standard digital test images
Standard test images provide a set of data that can be used for any of the following tasks:
— evaluating the colour reproduction of imaging systems;
— evaluating colour image output devices;
— evaluating the effect of image processing algorithms applied to the images;
— evaluating the coding technologies necessary for the storage and transmission of high-definition
image data.
Because they exist as standard, well-defined, high-quality image data sets, typical of the range of image
content commonly encountered, they enable users to be confident that the images will produce good
quality reproductions, if properly rendered, and that they provide a reasonable test of the evaluation
task being undertaken. No limited set of images can fully test any system, but the sets provided give
as reasonable a test as can be expected from a limited image set. Furthermore, the existence of a
standard image data set enables users in different locations to produce comparisons without the need
to exchange images prior to reproduction.
However, different applications require that the standard image data be provided in different image
states using different image encodings (see ISO 22028-1). The user needs to select those appropriate to
the evaluation task being undertaken. Whilst transformation of the image data to another image state
is always possible, there is, in general, no agreement amongst experts as to how this is best done. Thus,
it has been considered preferable to provide data in three different image states in the various parts of
ISO 12640.
ISO 12640-1 provides a set of 8-bits-per-channel data that is defined in terms of CMYK dot percentages.
The colours resulting from reproduction of CMYK data are strictly defined only at the time of printing
and, as such, the data are only applicable to evaluation of CMYK printing applications. Transformations
to other image states and colour encodings are not necessarily well defined. In fact, the data might not
even be useful for CMYK printing processes different from those typically found in traditional graphic
arts applications as the image data are defined to produce “pleasing” images when reproduced on
systems using “typical” inks and producing “typical” tone value rendering. Printing systems that use
inks of a distinctly different colour, or produce a very different tone value rendering, will not reproduce
them as pleasing images without a well-defined colour transformation. Moreover, with a bit depth of
only 8 bits per channel, any colour transformation employed will probably introduce artefacts.
ISO 12640-2 provides a set of test image data encoded both as XYZ tristimulus values with a depth of
16 bits per channel and as sRGB (defined in IEC 61966-2-1) with a bit depth of 8 bits per channel. (The
higher bit depth for the XYZ encoding is necessary because of the perceptual non-uniformity of the
XYZ colour space.) Both sets of data are optimized for viewing on a reference sRGB CRT display in the
reference sRGB viewing environment, and relative to CIE standard illuminant D65 for which the XYZ
values were computed. The images are mainly designed to be used on systems utilizing sRGB as the
reference encoding, and as such are mainly applicable to the consumer market and those systems for
which the colour monitor is the “hub” device. Although such systems are used for some applications
in the graphic arts industry, sRGB is by no means the most common image encoding. Furthermore, a
particular drawback is the fact that the sRGB colour gamut is quite different in shape than the colour
gamut of typical offset printing. This difference can necessitate fairly aggressive colour re-rendering to
produce optimal prints from sRGB image data.
In order to be useful for applications where large, print-referred output gamuts are encountered,
common in graphic technology and photography, it was felt that it would be desirable to produce an
image set in which some colours are permitted to be encoded close to the boundary of the full colour
gamut attainable with surface colours. Furthermore, from the perspective of colour management it
is advantageous if the images are referenced to illuminant D50, which is the predominant reference
v
© ISO 2022 – All rights reserved

---------------------- Page: 5 ----------------------
ISO/FDIS 12640-3:2022(E)
illuminant used in graphic arts and photography, both for viewing and measurement. For this reason it
has also become the predominant reference illuminant for most colour management applications.
The purpose of this document is, therefore, to provide a test image data set with a large colour gamut
related to illuminant D50. The bit depth of the natural images is 16 bits per channel, while the colour
charts and vignettes are 8 bits per channel.
0.2 Definition of the reference colour gamut
The reference colour gamut defined for this document originated from three quite separate sources.
However, it was noted that there was considerable similarity between the three. One definition came
from work within ISO/TC 130 itself, and this arose by consideration of various sets of published data,
which together were taken to define the colour gamut of surface colours. The other definitions arose
from work within Hewlett-Packard, which was focused on the colour gamut obtainable by printing, and
that of a group of German photographic printing experts. The similarity of these led to the conclusion
that it is desirable to reconcile them into a single gamut that would be taken as the reference colour
gamut for this document. Full details of the reference colour gamut and its derivation are given in
Annex B.
0.3  Characteristics of the test images
The performance of any colour reproduction system is normally evaluated both subjectively (by
viewing the final output image) and objectively (by measurement of control elements). This requirement
dictated that the test images include both natural scenes (pictures) and synthetic images (colour charts
and colour vignettes). Because the results of subjective image evaluation are strongly affected by the
image content, it was important to ensure that the natural images were of high quality and contained
diverse subject matter. However, by requiring images to look natural, it is difficult within a single,
relatively small sample set to produce elements in the scene that contain the subtle colour differences
required in such test images and that cover the full reference colour gamut defined. It is also important
to have some images that contain subtle differences in near-neutral colours. Thus, while most images
contain colours that extend to the gamut boundary, this is often only for a limited range of hues in each
image. The full reference colour gamut can only be explored by utilizing the synthetic colour chart.
A survey was conducted of all ISO/TC 130 member countries to identify desirable image content and
to solicit submission of suitable images for consideration. The image set that resulted consists of eight
natural images, eight colour charts and two colour vignettes. The natural images include flesh tones,
images with detail in the extreme highlights or shadows, neutral colours, brown and wood-tone colours
that are often difficult to reproduce, memory colours, complicated geometric shapes, fine detail, and
highlight and shadow vignettes. The colour charts and colour vignettes show the reference colour
gamut (in CIE Lab colour space) in cross-sections for 16 and 8 hue angles, respectively.
0.4  File format of the digital test images
* * *
All of the images consist of pixel interleaved data (L then a then b ) with the data origin at the upper
left of the image, as viewed naturally, and organized by rows. These data are available as individual
files, which are a normative part of this part of this document. The image file format is as specified
in ISO 12639:2004, Annex H, with BitsPerSample set to 16, 16, 16. The images can be imported and
manipulated as necessary by a wide variety of imaging software tools and platforms commonly in
general use in the industry. See Annex D for details of the TIFF header.
1)
All colour charts and vignettes consist of files in Adobe® PDF format.
1) This information is given for the convenience of users of this document and does not constitute an endorsement
by ISO of the product named.
vi
  © ISO 2022 – All rights reserved

---------------------- Page: 6 ----------------------
FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 12640-3:2022(E)
Graphic technology — Prepress digital data exchange —
Part 3:
CIELAB standard colour image data (CIELAB/SCID)
1 Scope
This document specifies a set of standard large gamut colour images (encoded as 16-bit CIELAB digital
data) that can be used for the evaluation of changes in image quality during coding, image processing
(including transformation, compression and decompression), displaying on a colour monitor and
printing. These images can be used for research, testing and assessing of output systems such as
printers, colour management systems and colour profiles.
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 document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 12639:2004, Graphic technology — Prepress digital data exchange — Tag image file format for image
technology (TIFF/IT)
ISO 13655, Graphic technology — Spectral measurement and colorimetric computation for graphic arts
images
ISO 22028-1, Photography and graphic technology — Extended colour encodings for digital image storage,
manipulation and interchange — Part 1: Architecture and requirements
PDF Reference: Adobe Portable Document Format, Version 1.4 3rd edition., Adobe Systems Incorporated,
(ISBN 0-201-75839-3)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
checksum
sum of the digits in a file that can be used to check if a file has been transferred properly
Note 1 to entry: Often, only the least significant bits are summed.
3.2
colour gamut
solid in a colour space, consisting of all those colours that are present in a specific scene, artwork,
photograph, photomechanical or other reproduction; or are capable of being created using a particular
output device and/or medium
[SOURCE: ISO 12640-4:2011]
1
© ISO 2022 – All rights reserved

---------------------- Page: 7 ----------------------
ISO/FDIS 12640-3:2022(E)
3.3
colour sequence
order in which the colours are stored in a data file
3.4
colour space
geometric representation of colour in space
Note 1 to entry: A colour space is usually of three dimensions
Note 2 to entry: This entry was numbered 845-03-25 in IEC 60050-45:1987
[SOURCE: CIE S 17:2020 ILV: International Lighting Vocabulary, 2nd edition, modified]
3.5
colour value
numeric values associated with each of the pixels
3.6
data range
range of integers for a given variable in between a minimal and maximal value
3.7
global colour change
change to the colours in an image (often selectively by colour region) applied consistently to all parts of
the image
Note 1 to entry: This is in contrast to a local colour change where selected spatial areas of an image are changed
separately from the rest of the image area.
3.8
orientation
specifies the origin and direction of the first line of data with respect to the image content as viewed by
the end user
Note 1 to entry: The codes used to specify orientation are contained in ISO 12639.
3.9
pixel
smallest discrete picture element in a digital image file
3.10
pixel interleaving
* * *
colour data organized such that the L , a and b colour space values for one pixel are followed by the
same sequence of colour values for the next pixel; the specific order of colour components is determined
by the ColorSequence tag as defined in ISO 12639
Note 1 to entry: Other forms of colour data interleaving are line and plane.
4 Requirements
This document consists of the images contained in the 18 image data files which are part of this
document. Their file names are listed in Table 4. The image characteristics of these data are described
in Clause 5 and the electronic data structure in Clause 6.
2
  © ISO 2022 – All rights reserved

---------------------- Page: 8 ----------------------
ISO/FDIS 12640-3:2022(E)
5 Data description and definition
5.1 Data set definition
The set of standard colour image data consists of eight natural (photographed) images and ten synthetic
images created digitally on a computer. The synthetic images consist of eight colour charts consisting
of various patches, each 10 mm square, and two colour vignettes. The natural images are identified as
N1 to N8, and each of them also has a descriptive name derived from the picture content (e.g. bride and
groom). The synthetic images are identified as CC1 to CC8, CV1 and CV2.
The images are identified by the designation CIELAB/SCID. The co-ordinates of the text insertion are
provided in Annex E.
NOTE The image set defined in this document is based on the large gamut defined in Annex B. Image sets
contained in other document are based on different gamuts and can be more suitable for use in evaluation of
other applications.
5.2 Colour encoding used in this document
5.2.1 Image data encoding
The image data encoding shall be in accordance with the requirements of ISO 22028-1.
[10]
The image data are the desired CIELAB colorimetry defined by CIE Publication 15 , and measured in
accordance with ISO 13655, of reproductions of the images on the reference medium, with the reference
medium white point selected as the colour space white point. The image data are output-referred,
[11]
having been rendered to the reference medium of the ICC.1:2004-04 perceptual rendering intent,
which is defined as a hypothetical print on a substrate specified to have a neutral reflectance of 89 %
(the reference medium white point) and the darkest printable colour on this medium is assumed to have
a neutral reflectance of 0,347 31 % of the substrate reflectance (the reference medium black point). The
rendering target colour gamut for the reference medium is specified in Annex B. The reference viewing
environment is based on standard viewing condition P2, as specified for graphic arts and photography
in ISO 3664, but extended in the following way: the surfaces immediately surrounding the image are
assumed to be a uniform matt grey with a reflectance of 20 %. The reference viewing environment is
also assumed to have a viewing flare of 0,75 % of the luminance of the reference white. The CIELAB
image data are encoded as specified in 5.2.3 and 5.2.4.
5.2.2 Image data arrangement
* * *
The image data are pixel-interleaved in the colour sequence of L then a then b (16 bits) for the natural
* * *
images and L then a then b (8 bits) for the colour charts and the vignettes. The arrangement of data
follows the scanning of each image from the upper left corner to the upper right, then moving to the
next lower horizontal line. The resolution is 12 pixels/mm for every natural image.
5.2.3 CIELAB image data (16 bits per channel)
The CIELAB data for the natural images are encoded as 16-bit integers per channel, derived by
* * *
multiplying the L , a and b values for each pixel with the corresponding value for the data range.
*
 
L
*
L =×round 65535
 
16bit
 
100
 
* *
aa=×round()256 (1)
16bit
* *
b =×round()256 b
16biit
* * * * * *
where L , a and b represent normalised 16-bit values of L , a and b .
16bit 16bit 16bit
3
© ISO 2022 – All rights reserved

---------------------- Page: 9 ----------------------
ISO/FDIS 12640-3:2022(E)
The data range of the values is:
* * *
L ∈{0.100}, a ∈{−128.+127} and b ∈{−128.+127},
* * * * *
L ∈{0.65 535}, a ∈{−32 768.+32 512} and b ∈{−32 768.+32 512}, a and b are
16bit 16bit 16bit 16bit 16bit
signed integers.
NOTE −32 678 = −128 × 256, and 32 512 = 127 × 256.
5.2.4 CIELAB image data (8 bits per channel)
The CIELAB data for the colour charts are encoded as 8-bit integers per channel, derived by multiplying
* * *
the L , a and b values for each pixel with the corresponding value for the data range.
*
 
L
*
L =×round 255
 
8bit
 
100
 
* *
aa=round() (2)
8bit
* *
b =round(bb )
8bit
* * * * * *
where L , a and b represent normalised 8 bit values of L , a and b .
8bit 8bit 8bit
The data range of the values is:
* * *
L ∈{0.100}, a ∈{−128.+127} and b ∈{−128.+127},
* * * * *
L ∈{0.255}, a ∈{−128.+127} and b ∈{−128.+127}, the a and b are signed integers.
8bit 8bit 8bit 8bit 8bit
5.3 Natural images
The characteristics of the eight natural images, shown in Figure 1, are given in Table 1.
Table 1 — Characteristics for natural images
Parameter Characteristics
Resolution 12 pixels/mm
* * *
Colour values 16 bits/channel L , a and b , with respect to illuminant D50 (defined as
* * *
media-relative, i.e. such that a white in the image has the L , a and b
values of 100, 0, 0)
File format ISO 12639:2004, Annex H, with BitsPerSample set to 16, 16, 16
This format also readable with TIFF 6.0 with extension, photometric
interpretation tag 8, CIELAB, signed encoding.
Label on image CIELAB/SCID
Image data orientation Horizontal scanning starting from top left and ending at bottom right
NOTE The natural images have been colour-rendered to produce the desired image colorimetry on the
reference print medium as described in Annex B. For the most part, the image colours will be within the reference
colour gamut. However, it is possible for some image colours to be slightly outside (this is somewhat dependent
on how the convex hull of the gamut is constructed). It is sometimes necessary to gamut map the results of colour
rendering and re-rendering processing to exactly fit the destination device colour gamut.
The description and typical usage of the natural images are given in Table 2. The descriptive names
of these images are given following the identification code. Figure 1 shows reduced size sRGB
reproductions of the natural images. Statistical and gamut data for each of the natural images are
* * *
shown in Annex F, as histograms of the L values and a versus b plots for each image, respectively.
4
  © ISO 2022 – All rights reserved

---------------------- Page: 10 ----------------------
ISO/FDIS 12640-3:2022(E)
Table 2 — Natural images
Name Aspect, image Description and typical usage
size
N1 Bride and groom Horizontal, Image of a bride wearing white clothes and groom wearing black
2 560 × 2 048 clothes. Used to evaluate the rendering of human skin tones and neu-
pixels tral colours, especially highlights and shadows.
N2 People Horizontal, Image consisting of five people wearing colourful clothes, sitting on a
2 560 × 2 048 dark leather couch. Used to evaluate the colour rendering of extreme-
pixels ly colourful objects in the presence of skin tones and neutrals.
N3 Cashew nuts Vertical, Image of dried fruits and filled containers used to evaluate tonal
2 048 × 2 560 and colour rendering, in particular adjustments for grey component
pixels replacement.
N4 Meal Horizontal, Image with widely recognizable cooked food
...

ISO TC 130 N 4703
Date: 2022-01-2504-29
ISO/FDIS 12640-3:2022(E)
ISO TC 130/WG 2
ISO TC 130/WG 2
Secretariat: SAC
Graphic technology — Prepress digital data exchange —
Part 3: CIELAB standard colour image data (CIELAB/SCID)
Technologie graphique — Échange de données numériques de préimpression —
Partie 3: Données d'images en couleur normalisées CIELAB (CIELAB/SCID)

---------------------- Page: 1 ----------------------
ISO/FDIS 12640-3:2022(E)
ISO/FDIS 12640-3:2022(E)
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland.

ii
© ISO 2022 – All rights reserved
ii © ISO 2022 – All rights reserved

---------------------- Page: 2 ----------------------
ISO/FDIS 12640-3:2022(E)
ISO/FDIS 12640-3:2022(E)
Contents Page
FOREWORD . IV
INTRODUCTION . V
1 SCOPE . 1
2 NORMATIVE REFERENCES . 1
3 TERMS AND DEFINITIONS . 1
4 REQUIREMENTS . 2
5 DATA DESCRIPTION AND DEFINITION . 3
5.1 DATA SET DEFINITION . 3
5.2 COLOUR ENCODING USED IN THIS PART OF ISO 12640 .3
5.3 NATURAL IMAGES . 4
5.4 SYNTHETIC IMAGES . 7
6 ELECTRONIC DATA . 11
6.1 IMAGE FILE CHARACTERISTICS . 11
6.2 IMAGE FILE FORMATS . 11
ANNEX A (NORMATIVE) GUIDANCE FOR USE OF DIGITAL DATA . 12
ANNEX B (INFORMATIVE) DEFINITION OF THE REFERENCE COLOUR GAMUT . 14
ANNEX C (NORMATIVE) CHECK-SUM DATA . 21
ANNEX D (INFORMATIVE) TYPICAL TIFF FILE HEADERS USED FOR IMAGE DATA . 22
ANNEX E (INFORMATIVE) TEXT INSERTION . 24
ANNEX F (INFORMATIVE) HISTOGRAM AND GAMUT PLOTS . 25
ANNEX G (INFORMATIVE) CIELAB VALUES IN COLOUR CHARTS . 29
BIBLIOGRAPHY . 33
Foreword . iv
Introduction . v
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 9
4 Requirements . 11
5 Data description and definition . 11
5.1 Data set definition . 11
5.2 Colour encoding used in this document . 11
5.2.1 Image data encoding . 11
5.2.2 Image data arrangement . 11
5.2.3 CIELAB image data (16 bits per channel) . 11
5.2.4 CIELAB image data (8 bits per channel) . 12
5.3 Natural images . 12
5.4 Synthetic images . 17
5.4.1 Colour charts . 17
5.4.2 Vignettes . 20
5.4.3 Synthetic image format . 22

© ISO 2022 – All rights reserved iii
iii
© ISO 2022 – All rights reserved

---------------------- Page: 3 ----------------------
ISO/FDIS 12640-3:2022(E)
ISO/FDIS 12640-3:2022(E)
6 Electronic data . 22
6.1 Image file characteristics . 22
6.2 Image file formats . 23
Annex A (normative) Guidance for use of digital data . 24
Annex B (informative) Definition of the reference colour gamut . 28
Annex C (normative) Checksum data . 36
Annex D (informative) Typical TIFF file headers used for image data . 38
Annex E (informative) Text insertion . 43
Annex F (informative) Histogram and gamut plots . 46
Annex G (informative) CIELAB values in colour charts . 1
Bibliography . 9


iv
© ISO 2022 – All rights reserved
iv © ISO 2022 – All rights reserved

---------------------- Page: 4 ----------------------
ISO/FDIS 12640-3:2022(E)
ISO/FDIS 12640-3:2022(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/directiveswww.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/patentswww.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 of the voluntary nature of standards, the meaning of ISO specific terms and expressions related
to conformity assessment, as well as information about ISO's adherence to the World Trade Organization (WTO)
principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 130, Graphic technology.
TheThis second edition of ISO 12640-3 is a minor revision which cancels and replaces the first edition (ISO 12640-
3:2007). The scope of the document remains unchanged.

), of which it constitutes a minor revision. The changes are editorial as shown belowfollows:
Normative reference: — CIE Publication 15:2004 washas been changed to CIE Publication 15 Colorimetry;
Definition— in 3.4, the definition of colour space: has been updated based on revision to CIE Publication 17 in 2020.
;
— in the Bibliography:, CIE S 17:2020 ILV washas been updated to: International lighting vocabulary, 2nd edition.
A list of all parts in the ISO 12640 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A complete
listing of these bodies can be found at www.iso.org/members.htmlwww.iso.org/members.html.

© ISO 2022 – All rights reserved v
v
© ISO 2022 – All rights reserved

---------------------- Page: 5 ----------------------
ISO/FDIS 12640-3:2022(E)
ISO/FDIS 12640-3:2022(E)
Introduction
0.1  Need for standard digital test images
Standard test images provide a set of data that can be used for any of the following tasks:
— evaluating the colour reproduction of imaging systems;
— evaluating colour image output devices;
— evaluating the effect of image processing algorithms applied to the images;
— evaluating the coding technologies necessary for the storage and transmission of high-definition image data.
Because they exist as standard, well-defined, high-quality image data sets, typical of the range of image content
commonly encountered, they enable users to be confident that the images will produce good quality reproductions,
if properly rendered, and that they provide a reasonable test of the evaluation task being undertaken. No limited
set of images can fully test any system, but the sets provided give as reasonable a test as can be expected from a
limited image set. Furthermore, the existence of a standard image data set enables users in different locations to
produce comparisons without the need to exchange images prior to reproduction.
However, different applications require that the standard image data be provided in different image states using
different image encodings (see ISO 22028-1). The user needs to select those appropriate to the evaluation task being
undertaken. Whilst transformation of the image data to another image state is always possible, there is, in general,
no agreement amongst experts as to how this is best done. Thus, it has been considered preferable to provide data
in three different image states in the various parts of ISO 12640.

Part 1 of ISO 12640-1 provides a set of 8-bits-per-channel data that is defined in terms of CMYK dot percentages.
The colours resulting from reproduction of CMYK data are strictly defined only at the time of printing and, as such,
the data are only applicable to evaluation of CMYK printing applications. Transformations to other image states and
colour encodings are not necessarily well defined. In fact, the data might not even be useful for CMYK printing
processes different from those typically found in traditional graphic arts applications as the image data are defined
to produce “pleasing” images when reproduced on systems using “typical” inks and producing “typical” tone value
rendering. Printing systems that use inks of a distinctly different colour, or produce a very different tone value
rendering, will not reproduce them as pleasing images without a well-defined colour transformation. Moreover,
with a bit depth of only 8 bits per channel, any colour transformation employed will probably introduce artefacts.

Part 2 of ISO 12640-2 provides a set of test image data encoded both as XYZ tristimulus values with a depth of
16 bits per channel and as sRGB (defined in IEC 61966-2-1) with a bit depth of 8 bits per channel. (The higher bit
depth for the XYZ encoding is necessary because of the perceptual non-uniformity of the XYZ colour space.) Both
sets of data are optimized for viewing on a reference sRGB CRT display in the reference sRGB viewing environment,
and relative to CIE standard illuminant D65 for which the XYZ values were computed. The images are mainly
designed to be used on systems utilizing sRGB as the reference encoding, and as such are mainly applicable to the
consumer market and those systems for which the colour monitor is the “hub” device. Although such systems are
used for some applications in the graphic arts industry, sRGB is by no means the most common image encoding.
Furthermore, a particular drawback is the fact that the sRGB colour gamut is quite different in shape than the colour
gamut of typical offset printing. This difference can necessitate fairly aggressive colour re-rendering to produce
optimal prints from sRGB image data.
In order to be useful for applications where large, print-referred output gamuts are encountered, common in
graphic technology and photography, it was felt that it would be desirable to produce an image set in which some
colours are permitted to be encoded close to the boundary of the full colour gamut attainable with surface colours.
Furthermore, from the perspective of colour management it is advantageous if the images are referenced to

vi
© ISO 2022 – All rights reserved
vi © ISO 2022 – All rights reserved

---------------------- Page: 6 ----------------------
ISO/FDIS 12640-3:2022(E)
ISO/FDIS 12640-3:2022(E)
illuminant D50, which is the predominant reference illuminant used in graphic arts and photography, both for
viewing and measurement. For this reason it has also become the predominant reference illuminant for most colour
management applications.
The purpose of this part of ISO 12640document is, therefore, to provide a test image data set with a large colour
gamut related to illuminant D50. The bit depth of the natural images is 16 bits per channel, while the colour charts
and vignettes are 8 bits per channel.
0.2  Definition of the reference colour gamut
The reference colour gamut defined for this part of ISO 12640document originated from three quite separate
sources. However, it was noted that there was considerable similarity between the three. One definition came from
work within ISO/TC 130 itself, and this arose by consideration of various sets of published data, which together
were taken to define the colour gamut of surface colours. The other definitions arose from work within Hewlett-
Packard, which was focused on the colour gamut obtainable by printing, and that of a group of German photographic
printing experts. The similarity of these led to the conclusion that it would beis desirable to reconcile them into a
single gamut that would be taken as the reference colour gamut for this part of ISO 12640.document. Full details of
the reference colour gamut and its derivation are given in Annex B.
0.3  Characteristics of the test images
The performance of any colour reproduction system is normally evaluated both subjectively (by viewing the final
output image) and objectively (by measurement of control elements). This requirement dictated that the test
images include both natural scenes (pictures) and synthetic images (colour charts and colour vignettes). Because
the results of subjective image evaluation are strongly affected by the image content, it was important to ensure
that the natural images were of high quality and contained diverse subject matter. However, by requiring images to
look natural, it is difficult within a single, relatively small sample set to produce elements in the scene that contain
the subtle colour differences required in such test images and that cover the full reference colour gamut defined. It
is also important to have some images that contain subtle differences in near-neutral colours. Thus, while most
images contain colours that extend to the gamut boundary, this is often only for a limited range of hues in each
image. The full reference colour gamut can only be explored by utilizing the synthetic colour chart.
A survey was conducted of all ISO/TC 130 member countries to identify desirable image content and to solicit
submission of suitable images for consideration. The image set that resulted consists of eight natural images, eight
colour charts and two colour vignettes. The natural images include flesh tones, images with detail in the extreme
highlights or shadows, neutral colours, brown and wood-tone colours that are often difficult to reproduce, memory
colours, complicated geometric shapes, fine detail, and highlight and shadow vignettes. The colour charts and colour
vignettes show the reference colour gamut (in CIE Lab colour space) in cross-sections for 16 and 8 hue angles,
respectively.
0.4  File format of the digital test images
* * *
All of the images consist of pixel interleaved data (L then a then b ) with the data origin at the upper left of the
image, as viewed naturally, and organized by rows. These data are available as individual files, which are a
normative part of this part of this part of ISO 12640.document. The image file format is as specified in ISO
12639:2004, Annex H, with BitsPerSample set to 16, 16, 16. The images can be imported and manipulated as
necessary by a wide variety of imaging software tools and platforms commonly in general use in the industry. (See
Annex D for details of the TIFF header.).

© ISO 2022 – All rights reserved vii
vii
© ISO 2022 – All rights reserved

---------------------- Page: 7 ----------------------
ISO/FDIS 12640-3:2022(E)
ISO/FDIS 12640-3:2022(E)
1
All colour charts and vignettes consist of files in Adobe® PDF format.

1
This information is given for the convenience of users of this document and does not constitute an endorsement by ISO of the product
named.


vii
© ISO 2022 – All rights reserved
viii © ISO 2022 – All rights reserved

---------------------- Page: 8 ----------------------
ISO/FDIS 12640-3:2022(E)
Graphic technology — Prepress digital data exchange — Part 3: CIELAB standard colour
image data (CIELAB/SCID)
1 Scope
This part of ISO 12640document specifies a set of standard large gamut colour images (encoded as 16-bit CIELAB
digital data) that can be used for the evaluation of changes in image quality during coding, image processing
(including transformation, compression and decompression), displaying on a colour monitor and printing. These
images can be used for research, testing and assessing of output systems such as printers, colour management
systems and colour profiles.
2 Normative references
The following referenced documents are indispensable forreferred to in the applicationtext 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 referenced document (including any amendments) applies.
ISO 3664, Viewing conditions — Graphic technology and photography
ISO ISO 12639:2004, Graphic technology — Prepress digital data exchange — Tag image file format for image
technology (TIFF/IT)
ISO 13655, Graphic technology — Spectral measurement and colorimetric computation for graphic arts images
ISO 22028--1, Photography and graphic technology — Extended colour encodings for digital image storage,
manipulation and interchange — Part 1: Architecture and requirements

CIE Publication 15, Colorimetry

ICC.1:2004-04, Image technology colour management — Architecture, profile format, and data structureT IFF,
Revision 6.0 Final, Aldus Corporation (now Adobe Systems Incorporated), June 3, 1992

PDF Reference: Adobe Portable Document Format, Version 1.4 3rd edition., Adobe Systems Incorporated, (ISBN 0-
201-75839-3)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
3.1
check sum
checksum
sum of the digits in a file that can be used to check if a file has been transferred properly

NOTENote 1 to entry: Often, only the least significant bits are summed.

9
© ISO 2022 – All rights reserved

---------------------- Page: 9 ----------------------
ISO/FDIS 12640-3:2022(E)
3.2
colour gamut
solid in a colour space, consisting of all those colours that are present in a specific scene, artwork, photograph,
photomechanical or other reproduction; or are capable of being created using a particular output device and/or
medium

[ISO 12231]

[SOURCE: ISO 12640-4:2011]
3.3
colour sequence
order in which the colours are stored in a data file
3.4
colour space
geometric representation of colour in space [CIE S 17:2020 ILV: International Lighting Vocabulary, 2nd edition]
Note 1 to entry: A colour space is usually of three dimensions
Note 2 to entry: This entry was numbered 845-03-25 in IEC 60050-45:1987
[SOURCE: CIE S 17:2020 ILV: International Lighting Vocabulary, 2nd edition, modified]
3.5
colour value
numeric values associated with each of the pixels
3.6
data range
range of integers for a given variable in between a minimal and maximal value
3.7
global colour change
change to the colours in an image (often selectively by colour region) applied consistently to all parts of the image

NOTE   Note 1 to entry: This is in contrast to a local colour change where selected spatial areas of an image are changed
separately from the rest of the image area.
3.8
orientation
specifies the origin and direction of the first line of data with respect to the image content as viewed by the end user

NOTE    Note 1 to entry: The codes used to specify orientation are contained in ISO 12639:2004.
3.9
pixel
smallest discrete picture element in a digital image file
3.10
pixel interleaving
* * *
colour data organized such that the L , a and b colour space values for one pixel are followed by the same sequence
of colour values for the next pixel; the specific order of colour components is determined by the ColorSequence tag
as defined in ISO 12639

10
© ISO 2022 – All rights reserved

---------------------- Page: 10 ----------------------
ISO/FDIS 12640-3:2022(E)

NOTE    Note 1 to entry: Other forms of colour data interleaving are line and plane.
4 Requirements
This part of ISO 12640document consists of the images contained in the 18 image data files which are part of this
part of ISO 12640.document. Their file names are listed in Table 4. The image characteristics of these data are
described in Clause 5 and the electronic data structure in Clause 6.
5 Data description and definition
5.1 Data set definition
The set of standard colour image data consists of eight natural (photographed) images and ten synthetic images
created digitally on a computer. The synthetic images consist of eight colour charts consisting of various patches,
each 10 mm square, and two colour vignettes. The natural images are identified as N1 to N8, and each of them also
has a descriptive name derived from the picture content (e.g. bride and groom). The synthetic images are identified
as CC1 to CC8, CV1 and CV2.
The images are identified by the designation CIELAB/SCID. The co-ordinates of the text insertion are provided in
Annex E.
NOTE The image set defined in this part of ISO 12640document is based on the large gamut defined in Annex B. Image sets
contained in other parts of ISO 12640document are based on different gamuts and can be more suitable for use in evaluation of
other applications.
5.2 Colour encoding used in this part of ISO 12640document
5.2.1 Image data encoding
The image data encoding is definedshall be in accordance with ISO 22028-1the requirements as followsof
ISO 22028-1.
[10]
The image data are the desired CIELAB colorimetry as defined by CIE Publication 15, , and measured in
accordance with ISO 13655, of reproductions of the images on the reference medium, with the reference medium
white point selected as the colour space white point. The image data are output-referred, having been rendered to
[11]
the reference medium of the ICC.1:2004-04 perceptual rendering intent, which is defined as a hypothetical print
on a substrate specified to have a neutral reflectance of 89 % (the reference medium white point) and the darkest
printable colour on this medium is assumed to have a neutral reflectance of 0,347 31 % of the substrate reflectance
(the reference medium black point). The rendering target colour gamut for the reference medium is specified in
Annex B. The reference viewing environment is based on standard viewing condition P2, as specified for graphic
arts and photography in ISO 3664, but extended in the following way: the surfaces immediately surrounding the
image are assumed to be a uniform matt grey with a reflectance of 20 %. The reference viewing environment is also
assumed to have a viewing flare of 0,75 % of the luminance of the reference white. The CIELAB image data are
encoded as specified in 5.2.3 and 5.2.4.
5.2.2 Image data arrangement
* * *
The image data are pixel-interleaved in the colour sequence of L then a then b (16 bits) for the natural images
* * *
and L then a then b (8 bits) fo
...