It is a very complicated issue to outline how to grasp the printing color.
The process plan for digitally sampling the film after it was actually put forward has actually been proposed for several years, and some foreign manufacturers have also tried it. However, due to the complexity of the printing color management theory and the high price of digital proofing equipment, the input-output ratio is not obvious, which greatly hinders the commercial development of the process.
In China, the first proofing after the film is still our main working method. Although some foreign equipment manufacturers have put forward the first technological process plan after digital proofing, it is still necessary to make a question mark. Because the existing color management theory does not completely solve the practical problems in the printing industry, even Adobe Corporation recommends in its Photoshop documentation that color space conversion should not be used in the printing design (CMYK image format).
We have accumulated years of research experience, and we have consulted with experts from relevant companies and master proofing printers. We have put forward a special and effective process plan on how to solve the problem of digital proofing performance and price ratio. If we solve the practical problem of digital proofing, then the process flow after proofing first can be correspondingly popularized.
First, determine the dot density is still the basis of the printing industry's work using Postscript driver and different PPD print properties file, can generate pre-separated Postscript file. The document is in fact device-related and can be sent to an imagesetter to produce films with different densities. The filming center, the proofing master, and the printing masters are all based on the density of the outlets to check the quality of the film and other links. It is not based on the hue of proofing or printing inks. In general, is it better to use U.S. ink or Japanese ink? Is it better to use Beijing-made ink or use Shanghai-made ink? Of course, the quality of the ink printed by different origins is good or bad, and the color (hue) is different. However, it is not possible to judge whether the design draft is correct or not, the quality of the film, and the quality of the printing.
The current digital proofing color management neglects the printing industry's reliance on the dot-based density work base. It only solves the proofing problem based on visual effects. It requires high-performance hardware and computationally complex algorithms. The corresponding result is high-priced input. And the operating costs did not really solve the problem effectively.
Second, the current prepress digital proofing program Most of the existing color digital proofing process is from color composite files to the printer, through the ICC profile document color correction, only supports RGB format. Although a small number of models support the CMYK format, they all have color shifts and cannot correctly restore colors. For color printers, most of the existing color printers are RGB. Although the print heads have four colors, six colors, or even seven colors, the internal interpretation is RGB mode. The colors are too saturated and the CMYK images cannot be correctly restored. Color. For printing color proofing, it is completely unacceptable. For medium and high-end color printers, PostScript or Postscript simulation printing can solve the problem of color reproduction of CMYK printing proofing to some extent. However, this method is based on the CIE color management method which is not fully mature at present. In the printing process, the CMYK data is converted into the data accepted by the printer according to the printer's ICC profile. The accuracy of the color depends on the correctness of the ICC profile. . Since the establishment of ICC profiles is related to the performance of the printers of each manufacturer, the performance of the printing inks, and the paper used, and the general ICC profile is based on the color correction of dozens of color blocks, it is not complete. The color reproduction, so the general performance of the printer is not suitable for pre-press color digital proofing.
For high-end digital proofing systems, such as: Imation Shine-sublimation proofer, Kodak's Approval XP proofer, Polaroid's PolaProof proofer, and a few other brands, their exquisite production level and their own color management system plus Careful correction of the ICC profile, the color effect has almost reached the level accepted by the printing industry. However, the problem that cannot be overlooked is that the prices of its equipment and software are blazingly high, generally between 5 and 200,000 US dollars. Not every company has such financial resources to purchase, and its performance and price ratio are not ideal.
Third, our research and ideas based on our proposed - pre-separation Postscript file is in fact equipment theory, we established the "Huawei color prepress digital proofing system" process. Avoiding complex proofing color management, using the same separated Postscript file as the discharged film or a grayscale PDF file distilled from the Postscript file, corresponding to cyan, magenta, yellow, and black The color separation produces a four-color composite or overlay proof on a single sheet of paper, which can completely solve the problem of color reproduction of CMYK. "Huawei color digital pre-printing proofing technology" is applied to low-end products and has obvious economic superiority. It can be used in high-end printers to achieve accurate color reproduction and printing simulation, and reduce hardware costs. The comparison of the old and new process flow is as follows:
1. Existing RGB color proofing: ICC profile can be used, only RGB mode is supported, and the color of CMYK image cannot be correctly restored.
2. Existing CMYK proofing: CMYK images → group files → (Postscript color composite files) → printing (print data of ICC profile correction). Due to the color conversion during printing, there are inevitable uncertainties in the color shift.
3.Huawei color digital pre-printing proofing process CMYK image → grouping file → pre-separated Postscript grayscale file (usually can be interpreted as a grayscale file of 4 pages, and can also be printed at this time) → usually divided into 4 Page grayscale PDF file → Print.
Mode 1 (thermal sublimation or thermal transfer printer) - First print the first page of the document in cyan (C) color, then print the second page of the document in magenta (M) color, then print the third page of the document The yellow (Y) color, the fourth page of the final printed document, in black (K) colors, is printed on a sheet of paper four times (different colors C, M, Y, K) to complete the color digital proofing of the entire print color. As for the spot color document, this method can also be used to print with the corresponding spot color printing ink (Note: Under normal circumstances, it is not possible to equip a variety of spot color printing inks. If the demand is not high, it can be printed in the batch file. The Postscript file stage will convert spot colors to process colors.) With regard to the problem of positional registration of the dichroic printing, the paper can be used without exiting and set to automatically return (Note: existing varieties of thermal transfer or sublimation printers already have the inherent function of paper retraction automatically), or Develop a new model (more suitable for large format), such as fixing the paper, and use the printer head X, Y direction to solve.
Mode 2 (color inkjet, color laser, or thermal printer) - A print driver can be designed to convert the separated Postscript grayscale file or distilled into a PDF grayscale file containing 4 pages. The M, Y, K color (or page) print data corresponds to the printer's C, M, Y, and K cartridges, or a new inkjet printer is designed, the paper is fixed, the printer head moves in the X and Y directions, and the four color separations occur. Print to achieve composite printing of CMYK color drafts.
Fourth, does not involve the existing complex color management "Huawei color prepress digital proofing process" is based on the existing Postscript printing, with the same consistency from the RIP to the imagesetter film, using the same pre-separation Postscript gray Degree file or grayscale PDF file to overcome the disadvantages of the existing digital pre-press proofing and inconsistent film ejection. The RIP photo discharge film is based on the process flow of CMYK decomposing to gray scale, while “Huawei Color Digital Proofing Process†uses the same principle to decompose CMYK into a grayscale file, but with further development, C, M, Y, K's corresponding four-page grayscale composite CMYK color proof on the same sheet of paper, has its own unique idea, skips the existing color management, and only uses the printer to restore linear grayscale images and graphics. The most basic function, based on black-and-white dot density, achieves the reduction of CMYK color printing, which completely solves the problems of color reproduction of high, medium, and low-end printers. The use of “Huawei Color Digital Proofing Technology†can also easily print out four-color color drafts, which meets the needs of the printing master in the traditional printing process.
5. Use of Postscript file format and PDF format “Huawei Color Digital Proofing Technology†follows Adobe’s industrial standards and directly uses previously-separated Postscript grayscale files or PDF files as the source files for color digital proofing.
"Huawei Color Digital Proofing Technology" uses pre-separated Postscript files or PDF-format grayscale files. The specific process is as follows: The assembled files can directly generate the C, M, Y, and K format of the discharged film through the Postscript driver. Separated Postscript files. The Postscript file is output to the imagesetter to produce four-color separation films, and “Huawei Color Digital Proofing Process†can also use this separated Postscript file to perform four-color separation and proofing and compound color on a single paper. Proofing, such as the traditional four-color composite proofing of the film and the printing of the PS plate, completely solves the problem of color reproduction of digital proofing before printing.
On the other hand, from the perspective of previewing and checking for errors in Postscript files, we first recommend using PDF files as a priority. Because Adobe's PDF format has the independence of the page and regards the Postscript code as "objects", the related information is included on each page, overcoming the problems of different types of RIP interpretation Psotscript file output with different differences.
From the separated Postscript file, we can distill it into a PDF file. Generally, four pages of the first page (C) color block, the second page of magenta (M) color block, the third page of the yellow (Y) color block, and the fourth page of the black (K) color block are obtained. Pages appear in grayscale. We know that regardless of the four-page gray-scale pages printed from the Postscript printing mode or the internal image-driven format, the dot images with different shades can be obtained, which has a clear and good printing effect. If black ink or ink is replaced with the corresponding cyan (C), magenta (M), yellow (Y), we can get a monochrome image. If the paper does not change, only the printing ink corresponding to different colors can be used to obtain a color composite proof on a single sheet of paper.
Sixth, on the issue of proofing the dot and ink color system Existing printers using a variety of technologies have reached 600 ~ 2400 points (emulation) resolution. Judging from the actual operation of the existing printing industry, various photosetters adopt different PPD files. The number of factory outlets, outlets, and network cables are not exactly the same. In fact, the printing industry only looks at the composition of each color block from the network size. The so-called ash, a few percent of the magenta, etc. are called.
The inks in different countries have different color differences, which leads to ink series in Japan, the United States, and Europe. The existing digital proofing system is based on different ink color corrections. The basic point of “Huawei Color Digital Proofing Technology†is that the Postscript file generated by the CMYK group file is actually related to the device, and there is no need to use color management to convert the device into a device-independent state, causing unnecessary color transfer. . "Huawei Color Digital Proofing Process" suggests that for the major different color printing inks, digital printing inks corresponding to color can be produced. With the unique printing process of “Huawei Color Digital Proofing Technology†separation and recombination, the correct color reproduction proofing of CMYK files is completed. This is the core of "Huawei Color Digital Proofing Technology".
VII. Compatibility and consistency with existing prepress and printing workflows Since “Huawei's digital pre-print proofing technology†conforms to the Postscript industry standard, it only uses its own proofing color management process in the digital proofing process. Say that there is no conflict with the existing prepress and printing workflows, achieving complete compatibility and consistency. Fully applicable to Postscript Level1, Level2 workflows, and Postscript3 workflows.
8. The support scope of “Huawei Color Prepress Digital Printing Proofing Process†supports all existing prepress proofing equipment;
Supports all existing prepress software, such as PageMaker, QuarkXPress, Illustrator, Corel