docs: def process_image(self, decorator):
          """
          # build out an image directive like
          # .. image:: somefile.png
          #    :width 4in
          #
          # from an input like
          # savefig somefile.png width=4in
          """
          savefig_dir = self.savefig_dir
          source_dir = self.source_dir
          saveargs = decorator.split(' ')
          filename = saveargs[1]
          # insert relative path to image file in source
          outfile = os.path.relpath(os.path.join(savefig_dir,filename),
                      source_dir)
  
          imagerows = ['.. image:: %s'%outfile]
  
          for kwarg in saveargs[2:]:
              arg, val = kwarg.split('=')
              arg = arg.strip()
              val = val.strip()
              imagerows.append('   :%s: %s'%(arg, val))
  
          image_file = os.path.basename(outfile) # only return file name
          image_directive = '\n'.join(imagerows)
          return image_file, image_directive