I know this works from the command line:
% convert ‘svn-book.pdf’ first-page.png
The above example will only process the first page of a PDF. This is
great for creating a thumbnail of the ‘cover page’ of a PDF, and it
avoids the CPU load required to process a huge file. (in this case,
the svn-book.pdf is 300 pages)
How would I accomplish this using the magick_file_column?
To use the command line as an example, the ‘svn-book.pdf’ isn’t
really and argument such as -size 120x120, etc. How can I pass that
 to rmagick when I’m processing a PDF?