Color Desktop Publishing Technology Q&A (2)

1. What is OPI technology? OPI (Open Press Interface) is actually a set of annotation specifications based on the Postscript language. These annotations indicate the relevant geometric parameters of the high-resolution file, where the currently saved file is on the network, and other parameters related to the communication network. The ability to centrally manage a large amount of image data, generate a preview of the OPI annotation and display, and complete the output management and image replacement functions of dedicated workstations, called OPI servers. The prepress system that uses the OPI method to circulate on its communication network is mainly an image with a much smaller capacity size and a layout file that is well-arranged. Since the capacity of the transferred file is small, the communication speed is accelerated and the production efficiency can be greatly improved. The server needs to store a large number of high-resolution image originals, requiring huge storage capabilities, communication capabilities, and the ability to control various output devices. Therefore, in an electronic prepress system composed of a plurality of workstations and related input and output devices, it is necessary to use a computer with high speed and capacity as a server. OPI's design concept is based on the concept of a network-centric concept. In the prepress system, all devices communicate with the web server, and the server becomes the production hub and dispatch center. 2. What are the functions of OPI/DCS server? Its main functions are: 1) Image file sampling. For registration on the server including high-resolution images provided in TIFF, DCS, Scitex CT and image compression format (JPEG, Quick Time), according to user requirements, produce preview files with specified resolution, and through the communication network For typesetting workstation calls. 2) Image file archiving management. For a large number of registered image files, network-wide management can be performed. The related image files can exist in any workstation on the network, and can also be managed, searched, indexed, and the like by other image database software. 3) For preview image compression. The resulting preview image can be further compressed in JPEG or QuickTime if the size is large. 4) Queuing management of output devices. The server can manage multiple Post script output devices simultaneously, including laser imagesetters, laser printers (black and white or color), and more. For each device, according to the output accuracy, the use of different modes (such as output negative film, Zhengyang film, anti-yang film, etc.) equipment different queues, and can achieve the automatic management of the output operation. 5) Limited management of output devices. Some output devices can specify a limited range of users to prevent unauthorized operators from operating erroneously. For jobs that have entered the queue for output, they can still be removed, deleted, moved to another queue, and other management operations by the operator. 6) Image substitution at the output. For the received Postscript output file, a search is performed automatically, and the output of the relevant file in which the high-resolution image is stored is replaced. 7) Job records. All the output device's job content, whether or not the error and related error information, output time, etc. are recorded for checking. 8) Color Management Technology. Supports color management technology. For the generated preview image, each device is matched and converted according to its purpose (monitor display or color printer proofing) to ensure good proximity to the printed product. 3. What are the aspects to consider when choosing an OPI server? When choosing OPI server, the following aspects need to be considered: 1) Supported file format types. Common file formats include TIFF (RGB), TIFF (CMYK), Scitex CT, DCS, EPS, PDF, PhotoCD (YCC) and others. 2) Whether it is possible to produce low resolution images with different resolutions as required. When outputting proofs to non-PS color prints, only preview images can be output. In practice, South Africa often prints proofs with medium resolution. Therefore, the OPI server should have the ability to produce preview images corresponding to the user's desired resolution. 3) Whether the OPI server can accurately reproduce the preview image. Since the preview image and the main image file are used independently of each other, whether or not the user's change of the preview image is accurately reproduced in the OPI server is crucial. These changes include frame rotation, rotation of the image with respect to the image, tilt deformation, scale change, overlapping of text and image, and different hiding relationships. 4) Whether to support the color management system. Support OPI server of the color management system, the low-resolution image produced can reflect the color appearance effect of the printed matter correctly. 5) Is there an image database function? After the server saves a large amount of image data, the retrieval of related image files, preview image files, and management of text files, directories, and indexes related to images are all different from common data structures. operation. 6) Whether to support different types of workstations. Publishing computer industry common computer system environment, including UNIX, MAC OS and Windows system. For Eastern language environment, OPI server should also consider whether to support the corresponding Chinese environment. 7) Some other features. Including: trapping, folding, and compression/decompression of image information. 4. What is Desktop Color Separation Format (DCS)? In the operation of the desktop publishing system, a larger amount of work is typesetting. The typesetting operator completes the final design and modification of the page, and other tasks such as scanning, color separation, and creativity are all services for typesetting. In actual work, a color separation device can often be provided for the needs of several typesetters. According to this operating situation, DCS mainly solves the problem of the transfer of images between scanning equipment and typesetting workstations. U.S. Quark, which is known for developing advanced desktop publishing software, proposed an effective and unusual solution for the transmission of a large number of images, and released the DCS file format, which was rapidly popularized. There are many color image processing softwares that support the DCS format, and Photoshop is one of them. After the color separation and trimming are completed, the files can be saved in the DCS format to form a file group consisting of 5 PS files. The first of these, called the Master, contains the address of each color separation file, the geometrical parameters of the image, and a low-resolution preview. The remaining four files are C, M, Y, and BK four-color color separation description files stored in the EPS format. The main file can be used independently from the other four files. Desktop systems that use DCS for production operations are flexible and do not require expensive servers. And it supports contoured images, which are widely used in desktop systems related prepress systems. 5. What kinds of software are commonly used in color desktop publishing? Commonly used software functions of color desktop publishing systems are often the same, the difference is that according to the purpose of use to strengthen a certain part of the function. At present, there are mainly the following categories: 1) Graphics processing software. With text input and title words, illustrations and a variety of charts design and production, editing and other functions. Can be expanded, reduced and deformed arbitrarily. 2) Image editing software. Can be used to solve continuous editing and editing of images. Including color correction, image adjustment, mask processing and image geometry changes. The production of special effects, including rotation, dimensional change, sharpness enhancement and softening, virtual shadow generation, tone adjustment, and color selective correction. 3) Color typesetting software. Mainly used to deal with color layout, including imposition and so on. Typesetting software can arrange text, graphics, and images in a single page. 4) Color separation software. The image form of RGB is separated into the image form of CMYK. 5) Folding software. Used to spell small pages into large page forms. 6) RIP. It is used to screen the page and rasterize the page. Some RIPs also include color separation. 7) Other multimedia software. 6. What is True Type font technology? True Type (TT) is a new digital font description technology jointly proposed by Apple Inc. and Microsoft Corporation. TT is a set of content-rich instruction sets that describe the contour outline of a font by a color numerical function. These instructions include font structure, color fill, digital description function, flow condition control, and raster processor (TT processor) control. Additional prompt information control instructions. TT uses the quadratic B-spline curve and straight line in geometry to describe the outline of the font. The second B-spline curve has first-order continuity and tangential continuity. The parabola can be accurately represented by a quadratic B-spline curve. A more complex font shape can be represented by the mathematical properties of the B-like long curve with several concatenated secondary B-spline curves and straight lines. The files describing TT fonts (including TT font description information, instruction sets, various tagging tables, etc.) may be commonly used on MAC and PC platforms. On the Mac platform, it is stored as a "Sfnt" resource and appears as a TTF file on the Windows platform. In order to ensure the cross-platform compatibility of TT, the data format of the font file is stored in a Motorola-style data structure (highest in the front, lower in the back). All TT interpreters on the Intel platform need to be properly pre-processed before they are executed. The Windows TT interpreter is included in its GDI (Graphics Device Interface), so any Windows-supported output device can be exported using the TT font. 7. What are the advantages of adopting True Type technology? TT technology has the following advantages: 1) The true WYSIWYG effect. Since TT supports almost all output devices, for the target output device, regardless of the system screen, laser printer, or laser imagesetter, all TT fonts installed in the operating system can be output at the specified resolution on the output device. Therefore, most typesetting applications can accurately lay out pages according to the current target output device resolution and other parameters. 2) Support font embedding technology to ensure cross-system transferability of files. TT technology embedded technology solves the problem of file and font consistency across systems. In the application, the saved file can be used to store all TT fonts used in the file in an embedded manner. Makes the entire file and the fonts it uses easily transferable to the same system used by other computers. The font embedding technology ensures that even if the computer used to receive the file does not have the font used for the transmitted file, the file can be saved in the original format by loading the TT font embedded in the file, and the original font can be used for printing and modification. 3) Operating system platform compatibility. Both the MAC and Windows platforms provide system-level TT support. Therefore, cross-platform compatibility exists between application files of the same name across different operating system platforms. If PageMaker is used on a Mac, if you have installed all the TT fonts used in the file, the final output produced by the file on the Mac will be highly consistent with the output under Windows. 4) ABC word width. Each character in the TT font has its own word width value. The word width description method used by TT is more perfect and scientific than the traditional PS Type 1. It uses ABC word width table, that is, the word width value of a traditional character is divided into three parts: A width is the blank space before placing the character outline, B width is the spacing of the character outline itself, C is the right side of the character outline White space. A+B+C is equivalent to the traditional word width value, and the A or C spacing can be negative, respectively, to produce a special typesetting effect. The use of ABC word width values ​​can avoid the cumulative rounding errors that are traditionally caused by the use of integer word width values. At the same time, you can avoid the unpredictable consequences when the last character of the end of the line is moved to the next line, or the output of the left first character cannot be aligned. The rounding error generated by the layout application when calculating the cumulative word width of a line can be distributed to the A and C intervals of each character in the entire line, ensuring the high accuracy of line breaking and the accuracy of user-defined left and right boundary dimensions. Sex. 5) Accurate font outline description. The TT technology uses a 2048*2048 grid space to define a traditional letter M space (the theoretical maximum allowable spatial range of the Cartesian coordinate system is 32767*32767 grid points), and the font original outline in this grid space. Digitized and therefore more suitable for high resolution output devices. Its performance can fully meet the general application of South Africa. Even when the resolution of the output device is greatly increased in the future, it is only necessary to use a higher grid space (4