Friday, December 16, 2011

New PDF Conversion Options

We are seeing an increasing number of reports of issues with converting PDF documents for faxing.

First, there is the increasing bulk and complexity of the latest Adobe Reader X.  Although you can be reasonably confident that any valid PDF can be opened with Adobe Reader, including the ones that Adobe actively prevent other software from processing, the principal problem we have seen is its habit of popping up message boxes asking you to check for updates.  Not a good idea if your system is doing lots of document conversions on an unattended server!  Adobe do an excellent job of shading colored pictures and logos, but this also creates a problem for faxing: it creates good quality TIF files but they are huge, and so take a long time to transmit.

For many years, our recommendation for users who had problems with Adobe products in Document Converter has been to try Ghostscript.  Although a little klunky to install, and subject to some variation from release to release, this at least does not attempt to 'phone home' for updates, and generally does a good job.  We have also added a few specialist options, such as the ability to create high-res faxes (300x300 and 400x400) from PDFs.  However Ghostscript also suffers from issues that have proved to be dealbreakers for some of our users: font rendering can be of less than perfect quality, half-tone and colored images and logos can easily become blocked white and black, and Ghostscript cannot handle a document which contains both portrait and landscape pages: the latter are truncated and occupy only part of the page.

To solve some of these issues, we have now added a built-in PDF converter to CVSINGLE, which requires neither Adobe or Ghostscript software to render PDFs to TIF.  And like Ghostscript, it does not need to use the Document Converter printer driver.  As well as creating compact and high-quality TIFs from text-based PDF originals, it is also highly customizable for optimizing color and gray-scale images, with many options which are selectable using the QPDF_OPTIONS variable. You can adjust the brightness or gamma of the image before dithering it to monochrome, choose various dithering methods, and force selected background levels to white. There is also edge-sharpening capability, and a de-speckle option. Mostly, these optimizations will more useful for fax 'applications' where you need to handle specific styles of PDF: for these, you can tune the parameters to balance readability and speed of transmission. But for all PDF document conversions, you will find that the new option is simple to use and provides a high-quality result. Customers have used these options to create faxes which are not only easier to read in TIF format but can also be transmitted in a fraction of the time taken by Adobe output from the same original PDFs.

So how do you select the new built-in PDF conversion?  There are basically three ways:

  • You can select it globally by adding an environment variable CVTOPTS with a value of 'Q'.
  • For use in job administration jobs or for general document conversion applications, add a  $convert_options QPDF  command to the UJP or USR file controlling the operation.
  • Finally, for single conversions, you can use a -Q command-line option when you run CVSINGLE.  

You can use the third method to experiment with different conversion methods: and using -G instead of -Q will select Ghostscript if you have it installed.  The renderer options can be selected with a CFG, UJP or USR variable QPDF_OPTIONS.

For complete documentation of the CopiaFacts built-in PDF converter, refer to this topic in the reference manual.