Additional PDF Parameters for annotations and AcroForms
This page applies to Harlequin v13.1r0 and later; and to Harlequin Core but not Harlequin MultiRIP.
The Harlequin RIP supports the printing of annotations and interactive forms, commonly called AcroForms.
A PDF file can contain information which is additional to the “normal” PDF format. When viewed using an interactive application such as Adobe Acrobat, this additional information provides interactive features making the page more like a form.
With features such as text input fields, multiple choice option lists and clickable buttons, a PDF file that features an AcroForm is used to provide comprehensive electronic form filling functionality.
An AcroForm is essentially for interactive use via a program like Adobe Acrobat. The Harlequin RIP, on the other hand, is not an interactive program, and is only concerned with rendering the contents of the PDF file for printed output. This creates a number of questions about exactly how and which of the essentially interactive features (for example, buttons and choice lists) should be printed.
When the user has completed his form, the PDF file is re-written by Acrobat to save the entered information. When this is done, it creates additional content in the PDF file called Appearance Streams which render the filled-in text input fields, buttons etc., exactly. It also marks the PDF file’s AcroForm as being “complete” (via the NeedAppearances key in the AcroForm dictionary being set to false ).
Conceptually, we can refer to such a file that has been completed in this way as being print ready .
Prior to being made print-ready, a PDF AcroForm may be incomplete to various degrees. The completeness of a PDF refers to two things:
- The fields’ appearance streams may not be present in the PDF file, even though the fields may have been given values (that is, the actual text to display in the input fields).
- The AcroForm is marked as incomplete by virtue of the
NeedAppearanceskey in the AcroForm dictionary being set totrue.
When the RIP is given the job of printing a PDF AcroForm, it has to be sensitive to whether or not the form has been completed and is print-ready. The rule is as follows:
- If the
NeedAppearanceskey in the AcroForm dictionary (in the PDF file) is given asfalse(or is absent), the AcroForm is printed such that all fields (and only those fields) with appearance streams given is displayed. Otherwise, ifNeedAppearancesis true, the RIP reconstructs appearance streams for all the fields it finds.
What this means for the Harlequin RIP is that, unless the PDF file has been made complete and print ready, the final appearance of the various fields of the AcroForm could be displayed slightly differently than might appear in the viewing application (for example, Acrobat).
The printing of print ready AcroForm field types (text fields, choice list boxes, butt and signature fields) is conditional upon the manner in which the fields have been defined in the AcroForm. For example, some button fields may have been flagged (by Acrobat) as “not to be printed” and so the RIP does not display such items.
OEMs are granted a certain amount of control over how the Harlequin RIP supports AcroForms, particularly with respect to how fields are formatted and rendered when the PDF file is not print ready.
This control is provided through a number of parameters specified in a portion of a PostScript language file submitted to the Harlequin RIP as part of its configuration. This PostScript file is called HqnPageSetupConf . This file resides in the SW/procsets folder.