The most popular cross media publishing feature of

2022-07-29
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The cross media publishing feature of PDF

postscript is designed for printing and publishing, and has become the de facto industrial standard of digital prepress technology: the multimedia application in PDF document format design has developed to a very high level, so it is suitable for printing and publishing and electronic publishing: after the emergence of web publishing, pdf has found its own place to play. Pdf meets the requirements of cross media publishing, because it is rooted in postscript technology, inherits all the advantages of this technology, and considers the needs and technical characteristics of electronic publishing. In addition, the PDF also integrates the display postscript technology to achieve the consistency between the hard copy output and the screen display effect

cross media publishing requires that after the design and production are completed, the work results can be used for a variety of publishing purposes, that is, one-time production and multiple use. Cross media publishing also requires that the production content have adaptive processing characteristics consistent with the publishing purpose, that is, relevant parameters can be set for a specific publishing purpose to adapt to the recording technology and media used in the publication

I. cross media publishing and its basic requirements

the basic task of cross media publishing can be summarized as "the processing, use and storage of data files can adapt to any kind of output". This basic task can also be used as the definition of the concept of cross media

it can be seen from the definition of cross media that it not only well summarizes and summarizes the relationship and technical characteristics between digital prepress and digital printing for the implementation of made in China 2025, but also reflects the new requirements of the growing social needs for the printing and publishing industry and the electronic publishing industry. At the same time, it also shows the wide applicability of this concept, that is, the cross media concept is aimed at traditional publishing The basic requirements for the cross use of electronic publishing and online publishing content. Cross media publishing requires that the content designed by users have some basic characteristics

1. adaptive processing characteristics of content

the content needs to be finished after it is made. The advent of electronic publishing system has reduced the requirements for professional knowledge of operators, and more and more people are engaged in the production of publication content. However, there is a misunderstanding on the fundamental problem that there are obvious differences between production and completion. Design and production is only the preliminary work of completing the dissemination of content. During this period, it may not be necessary to take into account the use objectives and recording media of the content, but it should not ignore the importance of the completion of the manuscript. After the design and production is completed, it should be targeted for specific communication methods and according to the recording technology and recording medium to be used. This process is called completion. After the cross media concept is put forward, completion becomes more important

taking the production content used for printing as an example, the page after processing should have adaptive processing characteristics for recording information using paper, ink, printing machine and specific printing process combination. For example, when the current page is in other color spaces, it should be converted to CMYK color space (this process is also called color separation in the digital prepress process). In order to compensate for the insufficient accuracy of the printing machine and printing plate and thus produce inaccurate overprint, it is necessary to make a trap for the page content. The spectrum can distinguish the elements of wear particles. According to the quality requirements and replication requirements of the printed matter, it is necessary to select different adding parameters and add bite marks on the relevant pages, Cutting marks, signal strips, etc. to facilitate plate installation, cutting and control printing quality

2. modify

everything in the world is in the process of development and change, and customer requirements may also change. In addition, the designed and produced content cannot be free from errors, such as errors in text input, graphical expression, etc. Therefore, cross media publishing requires that the produced content can be corrected before output, so as to reduce losses and create good conditions for cross media publishing

3. data format conversion

for the production process of all publication contents using digital equipment and digital technology, different publishing methods have different requirements for the digital file format, which depends on the characteristics of the recording medium and the mode of transmission of the publication. Therefore, data format conversion should be carried out as required after content production, such as converting documents used for printing and publishing to postscript, EPS or PDF format, and converting documents used for web publishing to HTML format

from the above-mentioned basic requirements for cross media, it is not enough for the effective implementation of cross media to rely on traditional output technology. It calls for new output technology, such as the supra structure successfully developed by Adobe on the basis of postscript level3 and PDF technology

II. Features of PDF suitable for printing and publishing

pdf suitable for printing and publishing is mainly divided into two aspects: first, it continues to support prepress and printing workflow; second, the description pages of each PDF are independent of each other

1. the importance of page independence

physically, a pootscript file describes the interconnected pages, which are arranged in the order of the contents of the publication. After being output on the hard copy equipment of various plastic granulators produced in, a continuous page sequence will be obtained. These pages have sequential, logical or causal relationships. In terms of file structure, each postscript file is actually a series of postscript instruction sets, which are divided into two parts: object definition and description. The description is about the description of the object. Because of this, it is possible to generate the correlation between the object and the object when the raw material temperature is heated to 100 ℃, and the correlation between the object and the object leads to the correlation of the page, because the related objects may be in different physical pages

the biggest drawback caused by page correlation is that it is very easy to make errors during output. For example, when rip interprets an object on page 5, it finds that it is related to the object on page 2, so rip needs to jump to page 2, reinterpret the object, and then return to page 5. If you only need to explain it again, it's not a big problem. It's a waste of time at most. However, the problem is that a related object may be reinterpreted after being reinterpreted. As a result of this reinterpretation, the interpretation will be nested multiple times, resulting in a limit error message or an overflow error from the postscript interpreter during output

The fundamental difference between PDF and postscript is that RDF is a document format rather than a page description language. Although it also describes objects, there is no programming structure, so pages are not related to each other. Therefore, after the "distillation" of acrobat distiller, an application that generates PDF files, the relevance between pages is cut off. It can be seen that the page irrelevant characteristics of PDF make it have the basic functions of cross media publishing. It can be used for print publishing, electronic publishing or web publishing without additional processing

2.pdf printing and publishing function

since PDF is based on postscript technology, there should be no doubt that it is based on continuous printing and publishing. However, the PDF format only provided limited printing and publishing functions in the early stage of its launch, and it did not become quite perfect until the release of acrobat3.0. Considering that there have been many articles on the printing and publishing function of PDF, we do not intend to discuss it in more space here. Collectively, PDF supports printing and publishing in the following ways:

(1) PDF, like postscript, uses a method similar to the printing process (template coloring) to generate objects, which is the most fundamental attribute of PDF:

(2) starting from version 1.2, PDF supports CMYK color spaces, which are necessary for printing and copying:

(3) every postscript file or EPS file is always related to the page, This is the main reason why the workflow based on PS or EPS files often produces limit inspection errors or overflow errors. However, when PS or EPS files are converted into PDF files, the relevance of pages is cut off, which can ensure that each PDF page can be output stably:

(4) support open prepress interface QPI (open prepress interface) to realize high-resolution image replacement, This is because digital images used for printing purposes usually have high spatial resolution and tonal resolution, so the storage capacity of image files is quite large. In order to reduce the burden of "handling", it is necessary to use low-resolution representative images in typesetting and replace them with high-resolution images when outputting:

(5) support composite font technology, and all required fonts in publications can be represented on the page

(6) support trapping to solve the problem that the existing printing equipment may show "white" on the edge of the object due to inaccurate overprint

(7) the built-in digital addition algorithm allows you to specify parameters such as point shape, number of lines and angle for different publishing requirements and printing quality

(8) support the clipping path, so that the clipping path output in the image processing software can be wrapped around the boundary of composition

(9) support color division images to realize the reproduction of monochrome prints in multiple levels, which is suitable for printing advanced prints of photographic pictures

(10) support color separation color space to facilitate the conversion from other image modes to CMYK mode

(11) it is provided to place bite marks, cutting marks, signal strips or gray ladders on some pages, which is conducive to the installation of plates before printing, the inspection of overprint accuracy and the inspection of print quality

pdf supports printing and publishing, but the above list is the main content

III. electronic publishing and online publishing features of PDF

pdf file format also considers the needs of electronic publishing in its design. The functions applicable to electronic publishing are also important for online publishing, because there is no difference in principle between electronic publishing and online publishing

pdf supports electronic publishing in many aspects. The main contents are introduced below

1. compression technology is necessary for electronic publishing and online publishing.

pdf adopts compression algorithms that meet industrial standards, such as JPEG, LZW, ccittgroup3, ccittgroup4, flat and run length coding, and can even compress embedded audio data. When using distiller to generate PDF files, users can specify different compression methods for different objects on the page, thus ensuring that PDF files are always light, flexible and easy to migrate. The reduction of file storage requirements for PDF reflects that it is suitable for both recording on CD and transmitting over the network

2. hypertext linking function

pdf supports hypertext and hypermedia links. An object on a page can be linked to another object as needed. We know that hypertext link is one of the basic features of multimedia electronic publications, so it is the main indicator to measure whether PDF has the function of electronic publishing. Hypertext links or hypermedia links ensure that PDF documents can be read in a non-linear way when displayed on the computer display screen. As long as users click the text or other objects marked with hypertext links or hypermedia links, they can access relevant content and return to the original place at any time

3. object description is device independent

each PDF file is described in a device independent way. In this way, each PDF file can be displayed on different computer platforms (such as personal computers and workstations) and different computer operating systems (such as windows, MAC QS and UNIX operating systems), and the results can be displayed

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