"Trapping" is a term that is widely used in the graphic arts industry. This term refers to the spreading and choking performed between two abutting colors. Trapping is used to avoid "flashes", in other words, unwanted white lines or color margins at color transitions that are the result of register errors in printing. The trapping option lets you add thin lines ("trap lines") to the margins of color transitions that cover the colors of other separations that may shine through or empty regions ("flash lines").
There is no trapping on separated input documents, i.e. the trapping parameters have no effect.
Trapping can take place on the basis of vector data (graphics) or pixel data (images). It is possible to trap graphic to graphic, graphic to image and image to image. Trapping within images is not supported.
"Document" group
"Override Settings from Document" option
Check this option if you want the trapping information that may be in the document to be overwritten by the trapping parameters set below.
"Add Settings as PDF Comment" option
All operations run by the "Trapping" engine are added as PDF annotations (comments) to the edited documents if you check this option.
"Retrap Trapped Pages" option
Activate this parameter if you want to retrap the documents with the parameters set below.
"PostScript Level 2, if possible" option
PostScript Level 2 does not support DeviceN color spaces correctly. This means that DeviceN color spaces are not reproduced correctly on PostScript Level 2 RIPs. If possible, traps are created without using the DeviceN color space when you enable this option.
"Limits" group
This group lets you specify restrictions regarding the complexity of page contents or runtime when you create trap lines.
"Maximum Size of Page Content" box and "When Maximum Size is Exceeded" parameter
In the automated mode (for example, during batch processing), this parameters prevent a long-running action from blocking job processing. You can set one of the following reactions if the size of the page content in a document exceeds a set data volume (MB):
| Cancel with error: The job is canceled and an error message issued. |
| Continue with warning: Processing continues; an alert message displays. |
| Ignore and continue: This condition is ignored. Processing continues irrespective of the data volume. |
Default: 10 MB.
"Maximum Number of Objects in Page Content" box and "When Maximum Number is Exceeded" parameter
This is where you can enter the maximum number of objects that a page may have.
Default: 10000 objects.
"Maximum Duration of Trapping" box and "When Maximum Duration is Exceeded" parameter
This is where you can enter the maximum time for trapping a document. When the set time is exceeded, the reaction follows the set rule.
Default: 10 minutes.
Behavior of the trapper with very complex PDF documents
It can happen that PDF documents that are to be trapped contain an extremely large number of objects that are to be trapped. One example of this is maps that are made up of a large number of vector elements. When processing such documents, it can happen that the trap engine would need several hours to process them and then at some point it would enter a "timeout" state.
In such a state, the Prinect workflow is paused until the trapping process is aborted or continued.
To avoid such a workflow stoppage, you can take the following precautions:
1.In the Prepare sequence, in the "Trapping" option on the "Document" tab in the "Limits" area, activate all limit parameters by setting the "Error" option in the "If maximum .... is exceeded" selection lists.
By checking these limits, the print job in question is checked. If one of the limits is exceeded, the current job is aborted with an error message, but the entire Prinect workflow is not blocked.
2.It is recommended, if possible, to check such complex documents with the PDF Toolbox Object Editor before processing these documents with the Prinect workflow. This can also be done after processing of the document has been aborted with an error message. The Object Editor can detect how many elements to be trapped in the document and whether this would cause the trap engine to time out. If in doubt, it may be safer to try trapping this document with the PDF Toolbox. If the number of objects to be trapped is too large, only the PDF Toolbox will time out and not the Prinect workflow. In this case, the PDF Toolbox can be terminated manually.
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