Cross-media publishing features of PDF
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Postscript is designed for print publishing and is the de facto industry standard for digital prepress technology: multimedia applications have been developed to a high degree in the design of PDF document formats, so it is suitable for print publishing and electronic publishing: after the emergence of online publishing , PDF still finds its own use.
PDF comes with features that meet the requirements of cross-media publishing, because it is rooted in PostScript technology, inherits all the advantages of the technology, and considers the needs and technical features of electronic publishing. In addition, the display of PostScript technology is integrated in the PDF to achieve consistency between the hard copy output and the screen display.
After cross-media publishing requires design and production, the results of the work can be used for a variety of publishing purposes, namely, one-time production and multiple use. Cross-media publishing also requires that the content be tailored to the purpose of publication, that is, the relevant parameters can be set for a particular publishing purpose to accommodate the recording techniques and media used in the publication.
First, 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", and this basic task can also be used as a definition of the concept of cross-media.
As can be seen from the definition of cross-media, it not only summarizes and summarizes the relationship and technical characteristics of digital prepress and digital printing, but also reflects the new requirements of the evolving social needs for the print publishing and electronic publishing industries: It also expresses the broad applicability of this concept, that is, the cross-media concept is a basic requirement for the cross-use of traditional publishing, electronic publishing and web publishing content. Cross-media publishing requires user-designed content to have some basic features.
1. Adaptive processing characteristics of content
After the content is created, it needs to be processed. The advent of the electronic publishing system has reduced the professional knowledge requirements for operators, and more and more people are engaged in the production of publication content, but there is a misunderstanding on the fundamental problem of significant differences between production and finalization. Design and production are just preliminary work to complete the dissemination of the content. During this period, it may not be necessary to take into account the use of the content and the recording medium, but it is not appropriate to ignore the importance of the final draft. After the design and production are completed, it should be targeted to the specific propagation method and according to the recording technology and recording medium to be used. This process is called finalization. After the cross-media concept is put forward, the finalization becomes more important.
Taking the production content for a print job as an example, the page should have an adaptive processing feature for recording information using a combination of paper, ink, printer, and a particular printing process. For example, the current page should be converted to CMYK color space in other color spaces (this process is also called color separation in the digital prepress process), in order to compensate for the lack of precision of the printing press and printing plate, resulting in inaccurate overprinting The content is to be compensated for the leakage process. For the quality requirements and copying requirements of the printed matter, different screening parameters should be selected, and the bite mark, the cutting mark, the signal strip, etc. should be added on the relevant page to facilitate the printing plate installation, cutting and controlling the printing quality, etc. .
2. modify
Everything in the world is in the midst of development and change, and customer requirements may change. In addition, it is impossible to design and produce good content without errors, such as errors in text input, errors in graphics, and so on. To this end, cross-media publishing requires that good content be edited and corrected before output to reduce losses and create good conditions for cross-media publishing.
3. Data format conversion
The publication content process for all digital devices and digital technologies has different requirements for digital file formats when it is published, depending on the recording medium characteristics and mode of dissemination of the publication. Therefore, data content conversion should be performed as needed after the content is created. For example, files for printing and publishing are converted to PostScript, EPS or PDF format, and files for web publishing are converted to HTML format.
From the above-mentioned basic requirements for cross-media, the effective implementation of cross-media is not enough by traditional output technology. It calls for new output technologies, such as Adobe's successful development based on PostScript Level3 and PDF technology. SUPRA structure.
Second, PDF is suitable for the characteristics of print publishing
The characteristics of PDF suitable for print publishing are mainly divided into two aspects: one is that it continues to support prepress and print workflows, and the other is that each PDF description page is independent of each other.
1. The importance of page independence
Physically, a PootScript file describes the pages that are connected to each other. They are arranged in the order of the content of the publication. After output on a hard copy device, a continuous sequence of pages is obtained. These pages have a sequence relationship, a logical relationship or a causal relationship. In the file structure, each PostScript file is actually a series of PostScript instruction sets, which are divided into object definition and description. The description is about the description of the object. It is because of this that it is possible to generate the object and the object. And the object's relevance to the object leads to the relevance of the page, because the related objects may be in different physical pages.
The biggest drawback of page correlation is that it is very error-prone when outputting. For example, when RIP interprets an object on page 5 and finds that it is related to the object on page 2, then RIP will jump to the second. Page, reinterpret the object and return to page 5. If you only need to re-interpret it once, the problem is not too big, and it is a waste of time. But the problem is that a related object may be interpreted again after being reinterpreted, so the result of repeated interpretation is the multiple nesting of the interpretation, which leads to the output of PostScript. The interpreter issues a limit error message or an overflow error.
The fundamental difference between PDF and PostScript is that RDF is a document format, not a page description language. Although it also describes objects, pages are not related to pages because there is no programming structure. So, after the application that generated the PDF file
After Acrobat Distiller "distilled", the page's relevance to the page was cut off. It can be seen that the page's irrelevant features make it suitable for cross-media publishing, and can be used for print publishing, electronic publishing or web publishing without additional processing.
2. PDF print publishing function
Since PDF is based on PostScript technology, it should be unquestionable for print publishing. However, the PDF format provided only a limited degree of print publishing in the early days of its launch, and it became quite perfect until the release of Acrobat 3.0. Considering that the print publishing function of PDF has been discussed in many articles, it is not intended to be discussed in more detail here. Put together, PDF support for print publishing is:
(1) PDF, like PostScript, produces objects using a method similar to the printing process (template coloring), which is the most fundamental attribute of PDF:
(2) Starting with version 1.2, PDFs begin to support CMYK color spaces, which are required for print copying:
(3) Every PostScript file or EPS file is always related to the page. This is the main reason that the PS or EPS file-based workflow often generates limit check errors or overflow errors, but when the PS file or EPS file is converted into After the PDF file, the page relevance is cut off, ensuring that each PDF page can be output stably:
(4) Support Open Prepress Interface (QPI) to achieve high-resolution image substitution, because digital images used for printing purposes usually have higher spatial resolution and tone resolution, thus image files. The storage capacity is quite large. In order to reduce the burden of "handling", it is necessary to use a low-resolution representative image in the typesetting, and replace it with a high-resolution image when outputting:
(5) Support complex font technology, all the required fonts in the publication can be displayed on the page;
(6) Support trapping to solve the problem that existing printing equipment may appear “white” at the edge of the object due to inaccurate overprinting;
(7) Built-in digital screening algorithm, which allows parameters such as dot pattern, screen line number and screen angle to be specified for different publishing requirements and printing quality;
(8) Supporting the clipping path, so that the cropping path outputted in the image processing software can be used as the boundary of the text winding;
(9) Supporting split-tone images to achieve monochrome prints with more layers of secondary numbers, suitable for printing high-quality prints of photographic images;
(10) Support color separation color space to facilitate conversion from other image modes to CMYK mode;
(11) Providing a bite mark, a cut mark, a signal strip or a gray scale on some pages, which facilitates the printing of the plate before printing, checking the overprinting accuracy, and checking the quality of the printed matter.
The functions of PDF support for print publishing can also be mentioned, but the main contents are listed above.
Third, PDF electronic publishing and online publishing features
The PDF file format is designed to take into account the needs of electronic publishing, and the functionality applicable to electronic publishing is equally important for online publishing because there is no principle difference between electronic publishing and online publishing.
PDF support for electronic publishing is manifested in several areas. The main content is selected below.
1. Compression technology is necessary for electronic publishing and web publishing
PDF uses industry-standard compression algorithms such as JPEG, LZW, CCITTGroup3, CCITTGroup4, Flate and run length encoding, etc., can even compress embedded audio data. User is using Distiller to generate PDF files can be specified with different compression methods for different objects on the page, thus ensuring that PDF files are always lightweight, flexible and portable. The reduction in PDF file storage requirements reflects the fact that it is suitable for both burning on a disc and for transmission over a network.
2. Hypertext link function
PDF supports hypertext and hypermedia links, and an object on the page can be linked to another object as needed. We know that hypertext links are one of the basic characteristics of multimedia electronic publications and are therefore the main indicators for measuring whether PDFs have electronic publishing capabilities. Hypertext links or hypermedia links are guaranteed PDF files can be read in a non-linear manner when displayed on a computer monitor screen. Users can access the content by clicking on text or other objects marked with hypertext links or hypermedia links, and can return to the original location at any time.
3. Object description is device independent
Each PDF file is described in a device-independent manner. In this way, each PDF file can be on different computer platforms (such as personal computers and workstations) and different computer operating systems (for example Displayed on Windows, Mac QS, and UNIX operating systems, and showing consistent results, is a fundamental requirement for electronic publishing.
4. Bookmarks and annotations
Bookmarks, annotations, and annotations can be added to PDF files. This is convenient for users who read PDFs on a computer screen, meaning that readers can stop reading at any time and return to their original location when needed. In addition, the reader can keep abreast of the amount of information related to the current reading, and record the reading experience in a timely manner.
5. Independent of resolution
The resolution of the page content is device-independent, that is, whether it is graphics, text or images, there is no need to consider the resolution when describing them, and only needs to be determined when outputting. This feature provides underlying support for electronic publishing and web publishing, meaning that PDF files can be output on any display device.
6. Support for multimedia content
Support for multimedia objects such as audio, video, and animation in the page, and multimedia objects can be compressed using a reasonable compression algorithm. Therefore PDF The format also applies to multimedia electronic publications and is not limited to traditional printed publications. The PDF can embed the multimedia object into the document, or can create a pointer to the multimedia source material file without embedding the document. At this time, when the reader wants to play the multimedia object, the multimedia application is called to call the multimedia material to play.
7. Mouse event
The PDF document format supports the response to mouse events. When an electronic publication or a network publication reader generates an action on the mouse, the PDF technology application intercepts the event represented by the action and initiates a link relationship with the multimedia material. The software suitable for the multimedia material plays the multimedia content in the PDF.
8. Reading of PDF documents
In order to promote the PDF document format, Adobe has adopted a reasonable strategy, and the company provides PDF document reading software to users of PDF documents free of charge. Acrobat Reader allows users to download the latest version of the software from the company's Web site via the Internet. When in use, readers can read PDF files directly on the screen and print them out on a hard copy device connected to a computer when needed. This way, readers can output PDF files on a regular desktop printer without having to purchase expensive PostScript hardware.
9. PDF file generation
The main way to generate PDF files is to use Acrobat Dstiller, but you can also generate PDF files directly in different applications. Now there are a lot of software built in this function, for example
IIIustrator, CorelDRAW, Photoshop, PageMaker and FreeHand. Also, if Acrobat 4.0 is installed on the user's system or 5.0, you can also use PDF in Microsoft Word 97 or 2000, Excel 97 or 2000, and PowerPoint 97 or 2000. Maker replaces the current document with a PDF.
10. PDF's soft encryption technology complies with copyright protection regulations
The built-in encryption method provided by the PDF format has the following functions: one document has two passwords, one is the password of the document owner (the creator of the PDF document), and the other is the password of the user (the user of the PD document). A document also defines actions that should be restricted even if the document has been decrypted, including printing, copying text and graphics out of the document, modifying the document, and adding or modifying text annotations. After the correct user password is entered, the PDF document is opened and decrypted, but the above operation is still limited: all operations are allowed only after the owner password of the PDF document is entered. The owner password is required to change the connected password, user password, and cancellation restrictions. Whether it is a user password, owner password, or operational restrictions on the document, the document is added to the document. However, only when a document has a user password, the user is prompted to enter the user's password when the document is opened.