graphviz pandoc filter

graphviz.py

#!/usr/bin/env python
# from https://gist.github.com/j9ac9k/92ec73ced404a4629b0f6487275dab54/

"""
Pandoc filter to process code blocks with class "graphviz" into
graphviz-generated images.
Needs pygraphviz
"""

import os
import sys
import pygraphviz

from pandocfilters import toJSONFilter, Para, Image, get_filename4code, get_caption, get_extension, RawBlock

def graphviz(key, value, format, _):
    if key == 'CodeBlock':
        [[ident, classes, keyvals], code] = value
        if "graphviz" in classes:
            caption, typef, keyvals = get_caption(keyvals)
            if format == 'html':
                g = pygraphviz.AGraph(string=code)
                g.layout()
                svg_string = g.draw(format='svg').decode()
                svg_without_doctype = svg_string.split("\n", 3)[3]
                return RawBlock("html", svg_without_doctype)
            else:
                filetype = get_extension(format, "png", html="png", latex="pdf")
                dest = get_filename4code("graphviz", code, filetype)

                if not os.path.isfile(dest):
                    g = pygraphviz.AGraph(string=code)
                    g.layout()
                    g.draw(dest)
                    sys.stderr.write('Created image ' + dest + '\n')

                return Para([Image([ident, [], keyvals], caption, [dest, typef])])

if __name__ == "__main__":
    toJSONFilter(graphviz)