Introduction to comment parsing

This page applies to Harlequin v13.1r0 and later; both Harlequin Core and Harlequin MultiRIP.

A common use of comments is to specify the location of higher-resolution versions of images, as in the Open Prepress Interface (OPI) and desktop color separation (DCS) specifications. The RIP supports OPI and DCS specially with procsets, whose configuration and use is described in OPI and DCS.

Among other uses, comment parsing enables the Harlequin RIP to:

Pick up OPI information to substitute high-resolution images for low-resolution ones.
Pick up DCS comments for similar purposes.
Identify the application that generated a job in order to make application-specific adjustments.
Get book-keeping information from a job (such as titles, dates, and bounding-boxes).
Get information about separations in pre-separated color jobs.
Keep track of numbered pages (for example, to omit some).

Comments in PostScript-language jobs are introduced by the symbol % and run to the end of a line where a line is delimited by carriage return (CTRL-M), line feed (CTRL-J) or both.

Comments serve two purposes:

They have the normal function of annotating the program. This is minimal in most PostScript language jobs because jobs are usually machine generated.
They give information about the structure of a job if they follow a standard form: for example, that specified in Adobe’s Document Structuring Conventions. [ATN-DSC3.0] and Appendix G of [RB2], but not [RB3], define the comments that form version 3 of the Document Structuring Conventions. Earlier versions are documented in Adobe technical notes.

Comments of the second kind are generally well structured, intended primarily for reading with a preprocessor. However the Harlequin RIP allows them to be executed by the interpreter directly, using PostScript-language constructs. Such comments usually start with two percent signs ( %% ), but provision is made for dealing with single percent signs as well (necessary for handling OPI comments, for example).