1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T T.24 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2015) SERIES T: TERMINALS FOR TELEMATIC SERVICES Still-image compression Test charts Standardized digitized image set Recommendation ITU-T T.24 ITU-T T-SERIES RECOMME
2、NDATIONS TERMINALS FOR TELEMATIC SERVICES Facsimile Framework T.0T.19 Still-image compression Test charts T.20T.29 Facsimile Group 3 protocols T.30T.39 Colour representation T.40T.49 Character coding T.50T.59 Facsimile Group 4 protocols T.60T.69 Telematic services Framework T.70T.79 Still-image comp
3、ression JPEG-1, Bi-level and JBIG T.80T.89 Telematic services ISDN Terminals and protocols T.90T.99 Videotext Framework T.100T.109 Data protocols for multimedia conferencing T.120T.149 Telewriting T.150T.159 Multimedia and hypermedia framework T.170T.189 Cooperative document handling T.190T.199 Tele
4、matic services Interworking T.300T.399 Open document architecture T.400T.429 Document transfer and manipulation T.430T.449 Document application profile T.500T.509 Communication application profile T.510T.559 Telematic services Equipment characteristics T.560T.649 Still-image compression JPEG 2000 T.
5、800T.829 Still-image compression | JPEG XR T.830T.849 Still-image compression JPEG-1 extensions T.850T.899 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T T.24 (11/2015) i Recommendation ITU-T T.24 Standardized digitized image set Summary The images in Recommendati
6、on ITU-T T.24 include the original eight “ITU-T reference images“ (the ITU-T was formerly known as the CCITT and so these images were referred to for years as the “CCITT images“), two bi-level test charts, a grayscale test chart, various screened half-tone images, electronically dithered images, com
7、puter-generated images, grayscale images and colour images. The purpose of this image set is to provide a consistent baseline for future work; for example, results of compression algorithm experiments and image quality tests can be compared by a broad range of users, knowing that the input image dat
8、a is identical. The specimens reproduced inside the Recommendation in the figures are given for illustration purposes and are not suitable for measurements. The 3rd edition to Recommendation ITU-T T.24 is the consolidated version of Recommendation ITU-T T.24 (1998) and Corrigendum 1 (that clarifies
9、text in Table 1 with respect to the file sizes of reference test images on a companion CD-ROM). Amendment 1 (2000) was withdrawn in 2016/02 due to the unavailability of the 1200 dpi version of the ITU-T reference images there prescribed. This Recommendation includes an electronic attachment availabl
10、e from https:/www.itu.int/net/itu-t/sigdb/genimage/test24.htm. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T T.24 1994-11-11 8 11.1002/1000/2510 2.0 ITU-T T.24 1998-06-18 8 11.1002/1000/4390 2.1 ITU-T T.24 (1998) Amd. 1 2000-02-10 8 11.1002/1000/4838 2.2 ITU-T T.24 (1998)
11、Cor. 1 2015-11-29 16 11.1002/1000/12680 3.0 ITU-T T.24 2015-11-29 16 11.1002/1000/12981 * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii
12、Rec. ITU-T T.24 (11/2015) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU
13、-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for stu
14、dy by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a
15、collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain
16、certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express req
17、uirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Rig
18、ht. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intelle
19、ctual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2016 All right
20、s reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T T.24 (11/2015) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation .
21、1 4 Abbreviations and acronyms 1 5 Conventions 2 6 Description of the standardized digitized image set . 2 6.1 Eight ITU-T reference images 2 6.2 ITU-T T.22 test chart No. 4 Black-white facsimile test chart BW01 12 6.3 Legibility test chart . 14 6.4 Bi-level half-tones 16 6.5 ITU-T T.22 test chart N
22、o. 5 Continuous tone test chart CT01 21 6.6 House with trees and house with sky . 22 6.7 ITU-T T.23 test chart No. 6 4-Colour printing facsimile test chart 4CP01 . 23 6.8 CCIR images 26 6.9 Colour images (CMYK colour space) 27 6.10 Colour images (RGB colour space) 31 6.11 Fingerprint and medical ima
23、ges (Grayscale) 35 6.12 Line drawing images 37 6.13 Fine arts images 40 6.14 Low-contrast grayscale images 42 Appendix I Black/white pixel counts 51 Appendix II Sun Raster image format 53 Bibliography. 54 Included electronic files Available from https:/www.itu.int/net/itu-t/sigdb/genimage/test24.htm
24、: CD-ROM 1: Eight ITU-T reference images, ITU-T T.22 test chart No. 4, Legibility test chart, Bi-level half tones, ITU-T T.22 test chart No. 5, Houses, T.23 test chart No. 6. CD-ROM 2: CCIR images, CMYK colour images, RGB colour images, Fingerprint and medical grayscale images, Line drawing images,
25、Fine arts images, Low-contrast grayscale images. iv Rec. ITU-T T.24 (11/2015) Introduction Test images have played an important role throughout the development of Group 3 and Group 4 facsimile. This Recommendation has been prepared with the goal of providing a standard set of images1 to facsimile ex
26、perimenters. The set includes images that have been used over the years plus new images that are applicable for grayscale and colour. The standard set of images will provide a consistent baseline for further work; for example, results of compression algorithm experiments and image quality tests can
27、be compared by a broad range of users, knowing that the input image data is identical. The set of images, stored on a compact disk read only memory (CD-ROM), is available from the ITU. 1 The test images reproduced in this Recommendation are not suitable for the tests. Rec. ITU-T T.24 (11/2015) 1 Rec
28、ommendation ITU-T T.24 Standardized digitized image set 1 Scope The development of image compression algorithms can be facilitated by performance comparisons to reference images and algorithms. This Recommendation provides a reference image set that is to be used as a consistent baseline for future
29、image compression work. For example, results of compression algorithm experiments and image quality tests can be compared by a broad range of users, knowing that the input image data is identical. The images in this Recommendation include the original eight “ITU-T reference images“ (also known as th
30、e “CCITT images“), two bi-level test charts, a grayscale test chart, various screened half-tone images, electronically dithered images, computer-generated images, grayscale images and colour images. The specimens reproduced in the figures inside this Recommendation are given for illustration purpose
31、s and are not suitable for measurements. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations an
32、d other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. T
33、he reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T T.22 Recommendation ITU-T T.22 (1993), Standardized test charts for document facsimile transmissions. 3 Definitions 3.1 Terms defined elsewhere None. 3.2 Terms def
34、ined in this Recommendation This Recommendation defines the following term: 3.2.1 YUV: YUV (also known as YCbCr) colour model represents the human perception of colour more closely than the red, green and blue (RGB) colour component model by emphasizing the higher sensitivity of human vision to lumi
35、nance (Y) than to colour information (U or Cb and Y or Cr). This is done by representing the luminance with a higher bit resolution than Cb and Cr. The relationship between YUV and RGB is defined in clause 2.5 of b-ITU-R BT.601. 4 Abbreviations and acronyms This Recommendation uses the following abb
36、reviations and acronyms: CCIR International Radio Consultative Committee (now ITU-R) 2 Rec. ITU-T T.24 (11/2015) CCITT International Telegraph and Telephone Consultative Committee (now ITU-T) CMYK Cyan, Magenta, Yellow and Key (black) JPEG Joint Photographic Experts Group RGB Red Green Blue SCID Sta
37、ndard Colour Image Data 5 Conventions None. 6 Description of the standardized digitized image set The following sub-clauses describe the various images of the ITU-T T.24 standardized digitized image set2 that are found in the electronic attachment to this Recommendation, as well as on the ITU-T Test
38、 Signal Database at https:/www.itu.int/net/itu-t/sigdb/genimage/test24.htm. NOTE The test images reproduced in the main body of this Recommendation are not suitable for tests. 6.1 Eight ITU-T reference images This image set is derived from the eight ITU-T reference images (formerly known as the “CCI
39、TT images“). The eight pages were originally digitized by the French Administration as 200 pels per 25.4 mm and were used in the Group 3 facsimile algorithm selection process, completed in 1980. The digitized images herein were produced from original-quality copies of the eight ITU-T reference image
40、s, made at the time that the Group 3 compression algorithm studies were being conducted. All of the pages are A4 size, which is 210 mm wide by 297 mm long. The resolutions selected for the scanning process (200, 300, 400 and 600 pels per 25.4 mm) were based on those specified in the Group 3 and Grou
41、p 4 Recommendations (200, 300 and 400 pels per 25.4 mm) plus 600 pels per 25.4 mm. The number of pels per line is determined from the resolution and the width of the page. For the A4 page width of 210 mm, a 200 pels per 25.4 mm scan gives 1654 pels per line. The 1654 pel width is not a convenient nu
42、mber for computer-based processing (not divisible by 8). To correct this condition, the charts were scanned to produce the nominal pels per line and lines per image shown in the Group 3 and Group 4 Recommendations. This means that the pages were centred and overscanned. (The chart itself is 210 mm w
43、ide, but the scan line is 219.46 mm wide.) The total number of bytes required to store each of the images, as a function of resolution (or sampling density), is shown in Table 1. The eight ITU reference documents are illustrated in Figures 1 through 8. 2 The specimens reproduced in the figures of th
44、is Recommendation are given for illustration purposes and are not suitable for measurements Rec. ITU-T T.24 (11/2015) 3 Table 1 ITU reference documents Figure number Image Description Dimensions Resolution (pixels/inch) (1 bit/pixel) Size (MBytes) Pixels Inches Width Height Width Height Figure 1 Doc
45、ument No. 1 English letter 1728 2592 3456 5184 2339 3508 4677 7016 8.64 8.64 8.64 8.64 11.70 11.69 11.69 11.69 200 300 400 600 0.48 1.08 1.93 4.34 Figure 2 Document No. 2 Circuit drawing 1728 2592 3456 5184 2339 3508 4677 7016 8.64 8.64 8.64 8.64 11.70 11.69 11.69 11.69 200 300 400 600 0.48 1.08 1.9
46、3 4.34 Figure 3 Document No. 3 French invoice 1728 2592 3456 5184 2339 3508 4677 7016 8.64 8.64 8.64 8.64 11.70 11.69 11.69 11.69 200 300 400 600 0.48 1.08 1.93 4.34 Figure 4 Document No. 4 French text 1728 2592 3456 5184 2339 3508 4677 7016 8.64 8.64 8.64 8.64 11.70 11.69 11.69 11.69 200 300 400 60
47、0 0.48 1.08 1.93 4.34 Figure 5 Document No. 5 French text figures 1728 2592 3456 5184 2339 3508 4677 7016 8.64 8.64 8.64 8.64 11.70 11.69 11.69 11.69 200 300 400 600 0.48 1.08 1.93 4.34 Figure 6 Document No. 6 French chart 1728 2592 3456 5184 2339 3508 4677 7016 8.64 8.64 8.64 8.64 11.70 11.69 11.69
48、 11.69 200 300 400 600 0.48 1.08 1.93 4.34 Figure 7 Document No. 7 Kanji 1728 2592 3456 5184 2339 3508 4677 7016 8.64 8.64 8.64 8.64 11.70 11.69 11.69 11.69 200 300 400 600 0.48 1.08 1.93 4.34 Figure 8 Document No. 8 Handwritten memorandum 1728 2592 3456 5184 2339 3508 4677 7016 8.64 8.64 8.64 8.64
49、11.70 11.69 11.69 11.69 200 300 400 600 0.48 1.08 1.93 4.34 NOTE 1 The users of the Recommendation may freely reproduce Figures 1 to 8 to check the quality of document facsimile transmission. NOTE 2 The values in the Size column are the uncompressed files sizes. The corresponding files on the CD-ROM are compressed. 4 Rec. ITU-T T.24 (11/2015) Figure 1 Document No. 1 English letter Rec. ITU-T T.24 (11/2015) 5 Figure 2 Document No. 2 Circuit drawing 6 Rec. ITU-T T.24 (11/2015) Figure 3 D
