1、BRITISH STANDARDBS ISO 12640-3:2007Graphic technology Prepress digital dataexchange Part 3: CIELAB standard colour imagedata (CIELAB/SCID)ICS 35.240.30; 37.100.99g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g
2、44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58Incorporating corrigendum September 2014BS ISO 12640-3:2007ISBN 978 0 580 88014 8Amendments/corrigenda issued since publicationDate Comments 31 October 2014 Pdf issued in CDROM formatThis British Standard waspublished under the authorityo
3、f the Standards Policy andStrategy Committee on 31 August 2007 The British StandardsInstitution 2014.Published by BSI StandardsLimited 2014National forewordThis British Standard is the UK implementation of ISO 12640-3:2007.The UK participation in its preparation was entrusted to Technical CommitteeP
4、AI/43, Graphic technology.A list of organizations represented on this committee can be obtained onrequest to its secretary.The publication does not purport to include all the necessary provisions of acontract. Users are responsible for its correct application.Compliance with a British Standard canno
5、t confer immunity fromlegal obligations.Reference numberISO 12640-3:2007(E)INTERNATIONALSTANDARD ISO12640-3First edition2007-07-15Graphic technology Prepress digitaldata exchange Part 3: CIELAB standard colour image data(CIELAB/SCID) Technologie graphique change de donnes numriques deprimpression Pa
6、rtie 3: Donnes dimages en couleur normalises CIELAB(CIELAB/SCID) ii iiiContents 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
7、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 .
8、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 BS ISO 12640-3:2007iv Foreword ISO (the International Orga
9、nization 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 establis
10、hed 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
11、. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. P
12、ublication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. 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 pate
13、nt rights. ISO 12640-3 was prepared by Technical Committee ISO/TC 130, Graphic technology. ISO 12640 consists of the 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 encoded standard colou
14、r image data (XYZ/SCID) Part 3: CIELAB standard colour image data (CIELAB/SCID) The following parts are under preparation: Part 4: Wide gamut display-referred standard colour image data (TBDencoded/SCID) Part 5: Scene-referred standard colour image data (RIMM/SCID) BS ISO 12640-3:2007vIntroduction 0
15、.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 imag
16、es; 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 w
17、ill 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,
18、 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 encoding
19、s (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 pre
20、ferable to provide data in three different image states in the various parts of ISO 12640. Part 1 of ISO 12640 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 pri
21、nting 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 tr
22、aditional 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 renderi
23、ng, 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 provides a set of test image data encoded both as XYZ tristimu
24、lus 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 re
25、ference 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 mar
26、ket 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
27、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 technol
28、ogy 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 BS ISO 12640-3:2007vi surface colours. Furthermore, from the perspective of colour management it is adv
29、antageous if the images are referenced 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. The purpose
30、 of this part of ISO 12640 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 r
31、eference colour gamut defined for this part of ISO 12640 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
32、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 gamuts obtainable by printing, and that of a group of German photographic printing experts. The similarity of these led to the
33、conclusion that it would be desirable to reconcile them into a single gamut that would be taken as the reference colour gamut for this part of ISO 12640. 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
34、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)
35、. 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 sma
36、ll 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 con
37、tain 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 an
38、d 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-t
39、one 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.
40、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
41、this part of ISO 12640. 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
42、details of the TIFF header.) All colour charts and vignettes consist of files in Adobe PDF format. BS ISO 12640-3:20071Graphic technology Prepress digital data exchange Part 3: CIELAB standard colour image data (CIELAB/SCID) 1 Scope This part of ISO 12640 specifies a set of standard large gamut colo
43、ur 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
44、 assessing of output systems such as printers, colour management systems and colour profiles. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edi
45、tion of the referenced document (including any amendments) applies. ISO 3664, Viewing conditions Graphic technology and photography ISO 12639:2004, Graphic technology Prepress digital data exchange Tag image file format for image technology (TIFF/IT) ISO 13655, Graphic technology Spectral measuremen
46、t 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 15:2004, Colorimetry ICC.1:2004-04, Image technology colour m
47、anagement Architecture, profile format, and data structure TIFF, Revision 6.0 Final, Aldus Corporation (now Adobe Systems Incorporated), June 3, 1992 PDF Reference: Adobe Portable Document Format, Version 1.4 3rd edn., Adobe Systems Incorporated, (ISBN 0-201-75839-3) 3 Terms and definitions For the
48、purposes of this document, the following terms and definitions apply. 3.1 check sum sum of the digits in a file that can be used to check if a file has been transferred properly NOTE Often, only the least significant bits are summed. BS ISO 12640-3:20072 3.2 colour gamut solid in a colour space, con
49、sisting 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 3.3 colour sequence order in which the colours are stored in a data file 3.4 colour space geometric representation of colours in space, usually of three dimensions CIE Publication 17-1987 (845-03-25) 3.5 colour value numeric values associated with each of the pixels 3.6 data range range of integers for a given variable
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