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GB/T 18721.3-2024 English PDF

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GB/T 18721.3-2024: Graphic technology - Prepress digital data exchange - Part 3: CIELAB standard colour image data(CIELAB/SCID)
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Standard ID	Contents [version]	USD	STEP2	[PDF] delivered in	Standard Title (Description)	Status	PDF
GB/T 18721.3-2024	English	774	Add to Cart	6 days [Need to translate]	Graphic technology - Prepress digital data exchange - Part 3: CIELAB standard colour image data(CIELAB/SCID)	Valid	GB/T 18721.3-2024

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Basic data

Standard ID	GB/T 18721.3-2024 (GB/T18721.3-2024)
Description (Translated English)	Graphic technology - Prepress digital data exchange - Part 3: CIELAB standard colour image data(CIELAB/SCID)
Sector / Industry	National Standard (Recommended)
Classification of Chinese Standard	A17
Classification of International Standard	37.100.99
Word Count Estimation	38,373
Date of Issue	2024-03-15
Date of Implementation	2024-03-15
Issuing agency(ies)	State Administration for Market Regulation, China National Standardization Administration

GB/T 18721.3-2024: Graphic technology - Prepress digital data exchange - Part 3: CIELAB standard colour image data(CIELAB/SCID)

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ICS 37.100.99 CCSA17 National Standards of People's Republic of China Printing Technology Prepress Data Exchange Part 3.CIELAB standard color image data (CIELAB/SCID) (ISO 12640-3.2022, IDT) Released on 2024-03-15 2024-03-15 implementation State Administration for Market Regulation The National Standardization Administration issued

Preface III Introduction IV 1 Scope 1 2 Normative references 1 3 Terms and Definitions 1 4 Requirement 2 5 Data Description and Definition 2 5.1 Dataset Definition 2 5.2 Color coding used in this document 3 5.2.1 Image Data Coding 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) 3 5.3 Natural Images 4 5.4 Synthetic Image 6 5.4.1 Color Table 6 5.4.2 Gradient Image 8 5.4.3 Composite Image Format 9 6 Electronic Data 9 6.1 Image file characteristics 9 6.2 Image file formats 10 Appendix A (Normative) Guidelines for the use of digital data 11 Appendix B (Informative) Definition of reference color gamut 13 Appendix C (Normative) Checksum Data 20 Appendix D (Informative) Typical TIFF file header for image files 21 Appendix E (Informative) Insert text 23 Appendix F (Informative) Histogram and Color Gamut Diagram 24 Appendix G (Informative) CIELAB values in color tables 27 Reference 31

Foreword

This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for standardization work Part 1.Structure and drafting rules for standardization documents" Drafting. This document is part 3 of GB/T 18721 “Printing Technology Prepress Data Exchange”. GB/T 18721 has been published as follows part. --- Part 1.CMYK standard color image data (CMYK/SCID); --- Part 2.Standard color image data based on XYZ/sRGB encoding (XYZ/SCID); --- Part 3.CIELAB standard color image data (CIELAB/SCID); --- Part 4.Wide color gamut standard color image data for display [AdobeRGB (1998)/SCID]; --- Part 5.Scene-related standard colour image data (RIMM/SCID). This document is equivalent to ISO 12640-3.2022 "Printing technology prepress data exchange Part 3.CIELAB standard color image Data (CIELAB/SCID)". Please note that some of the contents of this document may involve patents. The issuing organization of this document does not assume the responsibility for identifying patents. This document is submitted by the State Administration of Press and Publication. This document is under the jurisdiction of the National Printing Standardization Technical Committee (SAC/TC170). This document was drafted by. Shenzhen Polytechnic, Anhui Caiyin Co., Ltd., Huaxin (Foshan) Color Printing Co., Ltd., Xingguang Printing (Suzhou) Co., Ltd., Shenzhen Ziguang Puyinjia Graphic System Co., Ltd., Guangdong Caile Intelligent Packaging Technology Co., Ltd., Liaocheng Product Quality Supervision and Inspection Institute, Zhiyuan Color Printing Industry (Huizhou) Co., Ltd., Guangdong Wangying Environmental Protection Packaging Industry Co., Ltd., Zhejiang Niannian Good Festive Products Co., Ltd., Shenzhen Hanson Software Co., Ltd., Wuqiao Jinding Ancient Books Printing Factory, Tianling Precision Plate Making (Shenzhen) Co., Ltd., Huiyuan Printing and Packaging Technology (Tianjin) Co., Ltd., Shanghai Publishing and Printing College, Guangdong Xingyi Digital Printing Co., Ltd. Co., Ltd., Shenzhen Yinzhi Internet Information Technology Co., Ltd., Shandong Tiancheng Testing and Certification Co., Ltd., Anhui Xinhua Printing Co., Ltd. company. The main drafters of this document are. Wu Li, Chen Xiulan, Wu Ning, Yu Hongming, Fan Haifeng, Deng Jinhua, Gong Rongrong, Zhu Qi, Huang Yunxin, Li Xiaoping, Huang Zongxiao, Li Longliang, Gu Qiusheng, Liu Chengwu, Zhou Changxing, Kong Lingjun, Huang Zhen, Xu Yun, Wang Xiufang, Du Wanquan, Zhang Xuliang, Chen Chen, Yang Siyu, Shuai Kefan, Wang Lijie, Li Yunxiang, Wang Lifen, Liu Haoxue, Liu Xia, Zheng Caihong, Chen Guangxue, Liang Yongjun, Su Xiaoyan, Liu Rong, Cui Yong.

Introduction

0.1 The need for standard digital test images The standard test images provide a set of data that can be used for any of the following tasks. --- Evaluate the color reproduction of the imaging system; --- Evaluate color image output devices; --- Evaluate the effectiveness of image processing algorithms applied to images; ---Evaluate the coding technologies required for storing and transmitting high-definition image data. As a well-defined dataset of standard groups, standard test images contain high-definition images with typical common image contents, which enable users to confirm We believe that, if mapped properly, this image will produce high-quality replicas and provide a reasonable test of the evaluation task. The image set provided in this document can fully test any system, but it can obtain reasonable testing expectations with a limited image set. The existence of datasets like these enables users in different regions to compare images without having to exchange images before copying them. However, different applications require standard image data to use different image encodings in different image states (see ISO 22028-1). The user needs to select the encoded image data that is suitable for the evaluation task. Although it is always possible to transform the image data into another image state, In general, there is no consensus among experts on how best to accomplish this task. Therefore, in each part of GB/T 18721, Data for three different image states is considered preferable. GB/T 18721.1 provides a set of 8-bit data per channel defined by CMYK dot percentage. The colors are strictly defined only when printed, so these data are only suitable for evaluation of CMYK printing applications and cannot be transferred to other image states. The state and color coding may not be well defined. In fact, because in traditional printing applications, these image data are defined in "Typical" ink systems and "typical" tone value mappings produce "satisfactory" images, while CMYK printing differs from this. Printing systems that use inks of significantly different colors or produce very different tonal value mappings may not be useful without clear Without a defined color conversion, the data will not be reproduced as a satisfactory image. In addition, with only 8 bits per channel In this case, any color change may produce artifacts. GB/T 18721.2 provides a set of test image data, which are encoded with XYZ values ranging from 0 to 65535 per channel, and Encoded in sRGB (defined in IEC 61966-2-1) with a bit depth of 8 bits per channel. (Due to the perceptual non-uniformity of linear color spaces The two sets of data are the same for viewing in the reference sRGB viewing environment and on the reference sRGB CRT display. The images are optimized and the XYZ tristimulus values are calculated relative to the CIE standard illuminant D65 before scaling. It is designed for systems that use sRGB as the reference encoding and is therefore primarily suitable for the consumer market and for those whose color displays are used as “distributed” devices. Although these systems have some applications in the printing industry, sRGB is definitely not the most common image encoding. A significant disadvantage is that the shape of the sRGB color gamut is very different from the typical offset color gamut. This difference may require more vivid colors to be re-colored. Mapping is done to produce the best printing results for sRGB image data. In common printing technology and photography, some application software involves large color gamut and printing-related output color gamut. In this case, it is considered desirable to produce an image set that allows encoding of full-gamut colors close to the boundaries of the achievable surface color gamut. In addition, from the perspective of color management, if the image uses the D50 reference illuminant, it is beneficial for both the observation and measurement of the image, because the The illuminant is the primary reference illuminant used in printing and photography. For this reason, it is also the illuminant used in most color management applications. The main reference illuminant. The purpose of this document is to provide a test image dataset with a large color gamut related to the illuminant D50.The bit depth of natural images is This document provides a set of test image data for a wide color gamut of reflective media, using D50 Illumination of the object. The bit depth of natural images is 16 bits per channel, while color tables and gradient maps are 8 bits per channel. For printing technology and photography In applications where large color gamuts are common in printing and printing-related output color gamuts, it is considered desirable to generate an image set that allows for close In addition, from a color management perspective, if the image adopts the main If you want to refer to the illuminant D50, it is beneficial for both observation and measurement of images. For this reason, this illuminant is also the reference illuminant for most color management applications. The main reference illuminant used. GB/T 18721.4 provides a set of wide color gamut test image data encoded as AdobeRGB with a bit depth of 16 bits per channel. These data are optimized for viewing under the AdobeRGB reference viewing environment and on an AdobeRGB reference monitor. RGB (1998) color image encoding specification]. These images are designed primarily for use with systems that use AdobeRGB as the reference encoding. This workflow is mainly suitable for the professional market and systems where wide color gamut color monitors are "distributed" devices. AdobeRGB is very popular among photographers and is increasingly used in printing technology. Closer to the typical offset printing gamut. Although this difference may require color remapping between AdobeRGB images and sRGB images, AdobeRGB -encoded images generally require less vivid color remapping when printed than sRGB -encoded images. Possible wide gamut color encoding options include AdobeRGB, opRGB (IEC 61966-2-5), and ROMM RGB. (ISO 22028-2). We hope to perfectly map the image on a well-defined large color gamut reference display through GB/T 18721.4. Therefore, AdobeRGB is preferred over the other two options. Since the color mapping integrity of opRGB is somewhat fuzzy, that is, when inputting ROMMRGB (ISO 22028-2) is not clear in output, so the reference medium and viewing conditions are slightly different. This is correct, but the reference medium is a virtual reflective print (ICC-perceived reference medium). Therefore, the image status is the same as this file. GB/T 18721.5 provides a set of scene-related test image data encoded as RIMMRGB, with the aim of providing a better resolution than sRGB. A test image dataset with a large color gamut, which is associated with the AdobeRGB wide color gamut display gamut. The bit depth is 16 bits per channel. These data are collected by various digital cameras and the original RGB signals of the cameras are converted into The accuracy of these estimates is affected by many factors, including the fact that the camera's spectral sensitivity is close to that of the human visual system. The degree of color matching function, the adequacy of the conversion from the camera raw RGB signal to the colorimetric estimate, such as signal off-axis attenuation, aberrations and glare The transformation to obtain the chromaticity estimate is a universal transformation, without any spectral characteristics specific to each scene. Therefore, in some cases, the color estimation may have obvious deviations. The image status of these data is scene-dependent The reason is that no attempt is made to produce a color mapping that will produce a satisfactory reproduction of the data on some output medium. The only processing of this data Based on visual evaluation, the adaptive white is selected. This is achieved by applying gain to the camera channels separately to achieve the desired white balance, which translates to scene-dependent, and then adjust the overall gain in a linear, scene-dependent workspace, while using ISO /T S22028-3.2012 The images are viewed using the color mapping transformation examples specified in Appendix A. For aesthetic reasons, a different white level may be desirable in some cases. If a different color mapping transform is used, a different overall gain may be required. The images provided in GB/T 18721.5 are mainly applicable to Used to evaluate color mapping for different output media. 0.2 Definition of reference color gamut The reference gamuts defined in this document have three quite different origins. However, it is noted that there are considerable similarities between the three. One definition comes from ISO /TC 130 itself, which takes into account various published data that together define surface The color gamut and the other two definitions come from specific digital printing equipment manufacturers and photography and printing experts. The similarity leads to the conclusion that it is desirable to merge them into a single color gamut. The gamut will be used as the reference gamut for this document. Full details of the reference gamut and its derivation are given in Appendix B. 0.3 Characteristics of test images The performance of any color reproduction system is usually determined both subjectively (by viewing the final output image) and objectively (by measuring the control components). This requirement requires that the test images include both natural scenes (photos) and synthetic images (color tables and color gradient maps). Since the results of subjective image evaluation are greatly affected by the image content, it is very important to ensure the high quality of natural images and contain a variety of subjects. However, since the images need to look natural, it is difficult to generate images containing this information in a single, relatively small sample set. The small color change elements required in the test image must cover the entire reference color gamut. It is also important that some images contain small variations in near-neutral colors. Therefore, while most images contain an extended color gamut The colors of the reference boundaries are usually only available for a limited range of tones in each image. The full reference gamut can only be obtained by using a composite color map table to achieve this. To determine the ideal image content, all ISO /TC130 member countries were surveyed and asked to submit appropriate The images were submitted for consideration, resulting in an image set consisting of 8 natural images, 8 color tables, and 2 color gradient maps. Skin tones, images with detail in extreme highlights or shadows, neutral colors, brown and wood tones that are often difficult to replicate, memory colors, complex Complex geometric shapes, fine details, and highlight and shadow gradients. The color table and color gradient map are respectively 16 and 8 hue angle cross-sections. The reference color gamut (in CIELAB color space) is shown above. 0.4 File formats for digital test images All images are composed of pixel interleaved data (first L*, then a*, then b*), with the origin of the data located at the upper left corner of the image. These data are provided as separate files and are a normative part of this document. GB/T 22113-2008 Appendix H stipulates that BitsPerSample is set to 16, 16, 16.These images can be used in various industries when necessary. TIFF file header. For more information, see Appendix D. All color tables and color gradients are available as files in Adobe􀆿PDF format. Printing Technology Prepress Data Exchange Part 3.CIELAB standard color image data (CIELAB/SCID) Important note. The electronic version of this document contains color information that is helpful for the correct understanding of this document. Therefore, users should consider using Print this document using a color printer. If you want to print in non-color, you can refer to the electronic version of this document.

1 Scope

This document specifies a set of standard wide-gamut color images (encoded as 16-bit CIELAB digital data) for use in evaluating encoding, image processing, and The changes in image quality during processing (including conversion, compression and decompression), display on color monitors and printing. This document is suitable for studying, testing and evaluating output systems such as printers, color management systems and color profiles.

2 Normative references

The contents of the following documents constitute the essential clauses of this document through normative references in this document. For referenced documents without a date, only the version corresponding to that date applies to this document; for referenced documents without a date, the latest version (including all amendments) applies to This document. GB/T 22113-2008 Printing technology Prepress data exchange Tagged image file format for image technology (TIFF/IT) (ISO 12639.2004, IDT) ISO 13655 Graphic technology - Spectral measurement and colorimetric calculation of printed images Note. GB/T 19437-2004 Printing technology Spectral measurement and colorimetric calculation of printed images (ISO 13655.1996, IDT) ISO 22028-1 Graphic arts and photography - Extended colour coding for digital image storage, manipulation and interchange - Part 1.Structure

3 Terms and definitions

The following terms and definitions apply to this document. 3.1 Checksum The sum of the digits in a file, used to check whether the file was transferred correctly. NOTE. Usually only the least significant digits are summed. 3.2 Color gamut All existing in a particular scene, draft, photograph, phototype, or other reproduction, or capable of being created using an output device and/or medium The colors constructed constitute the color solid in the color space.

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