The principle and practical method of realizing hand-made imposition of PS files (2)

Second, the relevant Postscript language

Although Postscript page description language has many descriptions. However, the imposition work only involves a small number of statements such as page size definition, coordinate translation, rotation, graphic state saving, and recovery.

XY Translate % shifts X horizontally in the current coordinate system and Y in vertical direction
Angle Rotate % rotates in the current coordinate system by an angle XY Scale % in the current coordinate system X scaled horizontally and vertically zoomed by 丫
A Clip % takes the current closed path A as the clipping path, the contents of the path are displayed, and other contents are cut off
/Save Save % Saves the current virtual memory status to /save. Save Restore % Restores to the previous virtual memory status. Gsave % Saves the current graphics status. Grestore % Restores the previously saved graphics status. Grestoreall % Restores to the most recently saved graphics status. % shows the current page

Third, the principle and steps of imposition

In the PS file is always a unit of page. The default coordinates of the page start from the origin of the coordinates. To achieve imposition. It is necessary to modify the original page size and coordinate system to print pages in different places. If you need to fold your hand, you must also rotate the page as required by your hand. Rearrange the order of the pages. The steps are as follows:

1. Set a new sheet size. Set the size of the large format (including the size of the bleeding and cutting lines) in accordance with the actual requirements of the imposition.

2. Save the original graphics state with the Gsave statement. Save the page's original coordinates, scale, and other image states. So that the original state can be restored after the imposition.

3. In print sheets, use the translation, rotation, and other statements to place the pages in the proper position in the printed sheet.

4. Remove the ShowPage statement of each page in the unit of print sheet, and add the page display statement ShowPage after all the page descriptions in the print sheet, so that each page can be displayed in the same printed sheet.

5. Use Grestore to restore the original graphics state. When necessary, additional information such as cutting lines, gray scales, and file names may be added.

6. Write the end of the corresponding PS file.

The default scale unit in the PS file is 1/72 inch, which is Point. Therefore, the value of the print size and the amount of translation must also be in units of points. For example, a 210mm × 285mm 16 open pages. The page size in points is 595×808. Here is the PS description that defines this page:

ppDSetup{
%%BeginFeature: *CustomPagesize True
595 808 0 0 1
4 dict begin
Dup /Oriention exch def
/Pageoffset[5 -2 roll]def
/Pagesize[
5 2 roll dup 0 eq exch 2 eq or{exch}if
Def
/ImagingBBox null def
Currentdict end
Setpagedevice
%%EndFeature
}PPDCleanup
To translate this page horizontally on the sheet, one page width. Use the following statement:
595 0 transate.

Fourth, the conclusion

Folding and imposition software are very useful software that can significantly increase work efficiency. Generally there are two ways to implement imposition: imposition of the EPS file and imposition of the PS file. Through the analysis of the contents of the PS file, the author used the second method to achieve imposition. And through the programming to achieve a folding and imposition function. After a preliminary test. You can implement layouts for PageMaker, QuarkXPress, Ms word, CoreDraw, and Wits. The characteristics of comparing these two imposition methods are:

1. The method of making a PS file is simple and easy to implement. It is convenient and fast to implement hand-folding and imposition for a multi-page PS file.

2. For several separate PS files, as long as the same size of layout is made with the same software, the imposition can also be easily implemented in this way.

3. Since the PS file is processed by imposition, the content and format of the PS file are related to the production software and the selected print driver. The PS files formed by different application software and different print drivers are also different and require different processing. This is the main limitation of this imposition method.

4. The use of the EPS file for imposition does not have the above-mentioned limitation of Article 3, so the flexibility will be higher. However, because the EPS file contains only a single page, multiple EPS files must be opened for imposition.



Source: PACK.CN