PDF color management workflow (3)

FreeHand. Like Xpress, you can place CMYK charts that have been optimally converted by the press in FreeHand, and then use appropriate property files for tagging when extracting device-independent PDF files. In addition, FreeHand's color management can also convert objects to a single CMYK color space when storing Postscript files. In this case, the characteristic file marked in Distiller will undoubtedly select the characteristic file for printing in FreeHand.

Office application software. In the software of Excel, PowerPoint, and Word, the colors of the students have common characteristics. First, regardless of the color space used in the color picker, these colors are written to the Postscript data stream in the DeviceRGB format. Therefore, using RGB percentages to define colors in these applications is obviously the best choice. Second, almost all three applications use a common color coding method; if all objects are assumed to use the correct profile, a series of tones created in each application will exhibit the same color appearance in the PDF. .

What is the correct profile for assigning RGB values ​​in office applications? Setting up Distiller with the correct profile and performance intent usually requires some experience. Experiments have shown that marking these colors with sRGB can cause color shifts; it is as if it were not defined in sRGB within the application software. The configuration that minimizes the color shift is flagged in the Adobe RGB (1998) profile.

Use Distiller as a reference. If you do not take into account Distiller's enormous effect on the Postscript interpreter, then any discussion of Distiller is incomplete. Postscript files that do not print the desired color effect can be reliably processed by using the "Leave Colors Unchanged" setting. Which device color should be used in the PDF file? If these color spaces or values ​​produce false or poor results, how do you combine the selection of these tag profiles to achieve a better look? And if different page objects need different profiles to get the best results, how will they be handled?

In order to solve the problem, first carefully observe Distiller's processing results, confirm that the problematic document has been diagnosed, and confirm that special PDF printing needs, such as color separation, are beyond the scope of Acrobat or Distiller. Therefore, they need a third-party solution.

Many vendors offer advanced tools for managing, checking, and changing PDF files. The products of Adobe, Enfocus and Lantana are typical representatives of various functions.

Adobe Inproduction. Adobe first started Inproduction in Acrobat 4.0. It provides many preflighting functions for making PDF files and modification tools that meet production requirements. The product is only version 1.0, and there are rumors that the product has disappeared. Although Inproduction can scan and record PDF 1.4 files, it is actually limited to use with Acrobat 4.05, and only supports PDF 1.3 and lower versions.

The main advantage of Inproduction is that it better identifies the ICCbased color space commonly used in device-independent PDF files. During the application process, we will find that some third-party plug-in solutions encounter compatibility issues when checking PDF files that are directly exported from the application software.

Enfocus PitStop. PitStop Professional 4.6, which costs about $400, is a tool for checking and modifying PDF files. It has most of the features of Adobe Inproduction and has an eye-catching larger toolkit for checking, correcting, and converting PDF files. In particular, it can add new page objects to existing PDF files, while also supporting the "sampling" function of other page objects, which can be used to select features such as colors and fonts. Of course, the software also has some limitations, such as font subsets and other issues.

PitStop's Inspector function can detect the type and attribute of any object in the page, and also allow the user to modify the attributes, such as re-assign the ICCbased page object's property file to the ICCbased page object. This feature is important for correcting PDF files that contain images from different software and Distill uses only the same feature file for processing. PitStop also has a "whole change" function that changes all the objects in the entire PDF document. For special colors, you can use the Image Color Matching palette to modify the image objects in the PDF file for optimal output consistency. PitStop Professional (and its $1,200 server version) is very useful for preflighting PDF files and can automatically correct many detected errors. In addition, Action Lists can also be used to complete corrective actions and automatically perform many procedures such as file reassignment. Preflight work is done using the "PDF Profiles" option, which defines in detail the features that PDF must include in a particular workflow.

Enfocus EyeDropper. The $30 EyeDropper is a tool for measuring the color values ​​of objects in PDF files. It can show the percentage of color or 8-bit value. It is a useful tool to ensure color quality. However, note that the software does not change the functionality of the PDF file.

Test Enfocus. The effectiveness of PitStop and EyeDropper will vary depending on the source of the PDF. For testing, we generated many device-independent PDF files using the techniques described earlier in this article, and then processed it using the now-released Enfocus tools - PitStop Pro 4.6 and EyeDropper 4.0, and noticed some anomalies.

(to be continued)