Archive for April, 2009

I finally snapped last week.

After years of writing verbose and repetitive setup.py files for my Python packages, I am unable to write another. Instead, I have started writing Pyron, a tool that gathers the same information by inspecting a Python package itself. Not only does this mean that I get to stop repeating myself, but that my projects will become much more uniform because package metadata will be represented through common conventions instead of explicit (and repetitive) configuration. Though Pyron is still very primitive, it has already allowed me to reduce simple packages to only a README.txt plus their actual Python source code.

Now that the excitement of PyCon 2009 is over, it is time for me to finish this brief series of blog posts on watermarking PDF files. In the first post I outlined how GraphicsMagick and Adobe Reader proved essential to the project for their ability to produce correct PDF files and then help me verify their correctness. The second post showed how an image can be applied as a watermark using the pdftk PDF Toolkit utility. The resulting watermark, after some margins had been added using a Python script, looked rather attractive:

Watermarked page (click for PDF). The light blue design is a PDF file that pdftk resizes and centers on the target document.

My last challenge was that, on certain pages, the watermark we were using had to be turned upside down. “Simple,” I thought, “I'll use pdftk to turn the watermark over before applying it!” I just had to process the watermark image with the letter S (“south”), which tells pdftk to rotate the image by 180°, and then use the result as the watermark:

$ pdftk arecibo2.pdf cat 1S output arecibo3.pdf
$ pdftk in.pdf background arecibo3.pdf output wmark3.pdf

Upside-down watermark (click for PDF). Whoops! After turning the watermark upside down, pdftk lost the ability to properly center it.