If the tool qpdf is available in the system, it will be called to manipulate the PDF files (especially to compress the PDF files).
qpdf(input, output, options = "--stream-data=compress")the path of the input PDF file
the path of the output (if missing, output will be the
same as input)
options for qpdf (default to be
'--stream-data=compress', i.e. compress the PDF files)
if ani.options('qpdf') is non-NULL, then this function
returns the status of the operation (0 for success; see
system); otherwise a warning will be issued
This is a wrapper to call qpdf. The path of qpdf should
be set via ani.options(qpdf = 'path/to/qpdf').
See the reference for detailed usage of qpdf.
Examples at https://yihui.name/animation/example/qpdf/
qpdf official website http://qpdf.sourceforge.net/