As the Charter library now needs to optionally save the chart as a vector-format PDF file, we need to find an alternative to the Python Imaging Library that supports writing to PDF files. There is one obvious candidate for this: ReportLab.
ReportLab is a commercial PDF generator, which is also released under an open source license. You can find out more about the ReportLab toolkit at http://www.reportlab.com/opensource/. The easiest way to install ReportLab is to use
pip install reportlab. If this doesn't work for you, check out the installation instructions at https://bitbucket.org/rptlab/reportlab for more details. Documentation for the ReportLab toolkit can be found at http://www.reportlab.com/docs/reportlab-userguide.pdf.
In many ways, ReportLab works in the same way as the Python Imaging Library: you initialize a document (called a canvas in ReportLab), call various methods to draw the elements onto the canvas, and then use the
save() method to save the PDF file to...