1、 ISO 2013 Graphic technology Prepress digital data exchange Part 5: Scene-referred standard colour image data (RIMM/SCID) Technologie graphique change de donnes numriques de primpression Partie 5: Donnes dimage standard en couleurs montres en rfrence par scne (RIMM/SCID) INTERNATIONAL STANDARD ISO 1
2、2640-5 First edition 2013-12-15 Reference number ISO 12640-5:2013(E) ISO 12640-5:2013(E)ii ISO 2013 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2013 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any mea
3、ns, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva
4、 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ISO 12640-5:2013(E) ISO 2013 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 1 4 Data description 4 4.1 G
5、eneral . 4 4.2 Data set definition 4 4.3 Image data arrangement 4 4.4 Data colour encoding . 4 4.5 Natural images 5 4.6 Synthetic images .19 5 Electronic data .23 Annex A (normative) Guidance for use of digital data 25 Annex B (normative) Check-sum data .27 Annex C (informative) T ypical TIFF/IT fil
6、e header used for image files 29 Annex D (informative) Label text insertion 31 Annex E (informative) Histogram and colour gamut 33 Bibliography .49 ISO 12640-5:2013(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member
7、 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
8、 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 ar
9、e 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
10、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
11、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 asse
12、ssment, as well as information about ISOs 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 Technical Committee ISO/TC 130, Graphic technology. ISO 12640 consists of the
13、following parts, under the general title Graphic technology Prepress digital data exchange: Part 1: CMYK standard colour image data (CMYK/SCID) Part 2: XYZ/sRGB standard colour image data (XYZ/SCID) Part 3: CIELAB standard colour image data (CIELAB/SCID) Part 4: Wide gamut display-referred standard
14、colour image data (Adobe RGB(1998)/SCID) Part 5: Scene-referred standard colour image data (RIMM/SCID)iv ISO 2013 All rights reserved ISO 12640-5:2013(E) Introduction 0.1 Need for standard colour image data Standard colour image data provide a set of data that can be used for any of the following ta
15、sks: 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, etc. These stan
16、dard, well-defined image data sets, are typical of the high quality image content commonly encountered when capturing and printing images. Users can therefore be confident that the images should produce good quality reproductions if properly rendered, and that they provide a reasonable test of the e
17、valuation 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 set enables users in different locations to produce comparisons without the need
18、to exchange images prior to reproduction. Different applications require that the standard image data be provided in different image states using different image encodings (see ISO 22028-1), so the user needs to select those appropriate to the evaluation task being undertaken. While transformation o
19、f the image data to another image state is always possible, there is, in general, no agreement amongst experts as to how this should be done. Thus, it has been considered preferable to provide data in different image states in the various parts of ISO 12640. The relationship between image states is
20、shown in Figure 1 along with the applicable parts of ISO 12640. ISO 2013 All rights reserved v ISO 12640-5:2013(E) Figure 1 Relationship between image states ISO 12640-1 provides a set of 8 bits/channel data that is defined in terms of CMYK dot percentages. The colours resulting from reproduction of
21、 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 might not be well defined. In fact, the data might not even be useful for CMYK printing proce
22、sses 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
23、, 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/channel, any colour transformation employed might well introduce artefacts. ISO 12640-2 provides a set of test image
24、data encoded both as XYZ values with each channel scaled to the range 0-65535, and as sRGB (defined in IEC 61966-2-1), with a bit depth of 8 bits/channel. (The higher bit depth for the XYZ encoding is necessary because of the perceptual non-uniformity of the linear colour space.) Both sets of data a
25、re optimized for viewing on a reference sRGB display in the reference sRGB viewing environment, and relative to CIE standard illuminant D65 for which the XYZ tristimulus values were computed prior to scaling. The images are mainly designed to be used on systems utilizing sRGB as the reference encodi
26、ng, and as such are primarily applicable to systems for which a colour monitor similar to the sRGB reference display is the “hub” device. Although such systems are used for consumer photography, they are less popular in the graphic arts industry because the sRGB colour gamut is quite different in sh
27、ape from the colour gamut of typical offset printing. This difference can necessitate fairly aggressive colour re-rendering to produce optimal prints from sRGB image data. ISO 12640-3 provides a set of test image data with a large reflection medium colour gamut, illuminated using illuminant D50. The
28、 bit depth of the natural images is 16 bits/channel, while the colour charts and vi ISO 2013 All rights reserved ISO 12640-5:2013(E) vignettes are 8 bits/channel. In order to be useful for applications where large, print-referred output gamuts are encountered, common in graphic technology and photog
29、raphy, 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 attained with surface colours. Furthermore, from the perspective of colour management, it is advantageous if the images are reference
30、d to 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. ISO 12640-4 provides a set of wide-gamut test i
31、mage data encoded as Adobe RGB with a bit depth of 16 bits/channel. These data are optimized for viewing on a reference Adobe RGB display in the reference Adobe RGB viewing environment (defined in the Adobe RGB (1998) Colour Image Encoding specification). The images are designed to be used mainly on
32、 systems utilizing Adobe RGB as the reference encoding, and as such are mainly applicable to the professional market and those systems for which the wide gamut colour monitor is the “hub” device. Such workflows are popular among professional photographers, and are increasingly used in the graphic ar
33、ts. The Adobe RGB reference display colour gamut is closer to typical offset printing gamuts than the sRGB reference display colour gamut. Adobe RGB encoded images generally require much less aggressive colour re-rendering going to print than sRGB encoded images, although this difference can necessi
34、tate colour re-rendering between Adobe RGB images and sRGB images. The purpose of ISO 12640-4 is therefore to provide a test image data set with a larger colour gamut than sRGB, related to the Adobe RGB wide-gamut display-referred colour space. The bit depth of the natural images and synthetic image
35、s is 16 bits/channel. The possible wide gamut colour encoding choices considered were Adobe RGB, opRGB (IEC 61966-2-5) and ROMM RGB (ISO 22028-2). For ISO 12640-4, it was important that the images were well-colour- rendered to a well-defined large gamut reference display, for which reason Adobe RGB
36、was preferred over the other two choices. With opRGB, the completeness of the colour rendering is left more ambiguous, i.e. it is not as clearly output-referred, and the reference medium and viewing conditions are also slightly different. ROMM RGB (ISO 22028-2) is clearly output-referred, but the re
37、ference medium is a virtual reflection print (the ICC perceptual reference medium), so the image state is identical to that for ISO 12640-3. This part of ISO 12640 provides a set of scene-referred test image data encoded as RIMM RGB with a bit depth of 16 bits/channel. These data are estimates of sc
38、ene colorimetry obtained by capturing natural scenes using a variety of digital cameras and transforming the captured raw camera RGB signals to scene colorimetry estimates. The accuracy of these estimates is influenced by a number of factors including the degree to which the camera spectral sensitiv
39、ities approximate human visual system colour matching functions, the appropriateness of the transformation from raw camera RGB signals to colorimetry estimates, optical effects such as off-axis decrease in signal, aberrations and flare, and the noise present in the camera signals. The transformation
40、s applied to obtain the colorimetry estimates were general transformations, i.e. they were not optimized for the spectral characteristics of each scene. Consequently, there can in some cases be significant errors in the estimates. The image state of these data is scene-referred because no attempt ha
41、s been made to colour render the data to produce a pleasing reproduction on some output medium. The only processing applied to these data based on visual evaluation was to select the scene adopted white. This was accomplished by applying gains individually to the camera channels to achieve the desir
42、ed white balance, converting to scene-referred, and then adjusting the overall gain in a linear, scene-referred working space while viewing the image with the example colour rendering transform specified in ISO/TS 22028-3:2012, Annex A, applied. Different white balances can be desired in some cases
43、for aesthetic reasons, and different overall gains can be needed if different colour rendering transforms are used. The images provided in this part of ISO 12640 are mainly applicable for evaluating colour rendering to different output media. 0.2 Characteristics of the test images The performance of
44、 any colour reproduction system will normally be evaluated both subjectively (by viewing the final output image) and objectively (by measurement of control elements). This requirement dictates that the test images include both natural scenes (pictures) and synthetic images (colour charts and colour
45、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 ISO 2013 All rights reserved vii ISO 12640-5:2013(E) diverse subject matter. However, it is difficult withi
46、n a single, relatively small, sample set to produce elements in the scene that contain all the subtle colour differences required in test images, and that span the full range of colours that can be encountered in real scenes. For this reason, synthetic colour charts are also included. These colour c
47、harts are limited by the integer RIMM RGB encoding and by the spectral locus (for areas where the RIMM RGB encoding extends outside the spectral locus). In the future, it is proposed to develop a second set of floating point RIMM/SCID which are not limited by the integer RIMM RGB encoding. To obtain
48、 the images, a survey was conducted of all 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 44 natural images, two colour charts and a series of colour vignettes. The natural images inc
49、lude flesh tones, hair, foliage, water, sky, flowers and other memory colours in scenes with a variety of dynamic ranges. 0.3 File format of the digital test images All of the images consist of pixel interleaved data (R then G then B), with the data origin at the upper left of the image, as viewed naturally, and organized by rows. These data are included as individual files within this part of ISO 12640. The image file format is as specified in ISO 12639 (TIFF/IT). A RIMM RGB ICC profile meeting the requirements of ISO 15076
