129 lines
3.2 KiB
Python
129 lines
3.2 KiB
Python
"""
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GraphViz Tag
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---------
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This implements a Liquid-style graphviz tag for Pelican. You can use different
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Graphviz programs like dot, neato, twopi etc. [1]
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[1] http://www.graphviz.org/
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Syntax
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------
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{% graphviz
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<program> {
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<DOT code>
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}
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%}
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Examples
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--------
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{% graphviz
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dot {
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digraph graphname {
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a -> b -> c;
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b -> d;
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}
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}
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%}
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{% graphviz
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twopi {
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<code goes here>
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}
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%}
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{% graphviz
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neato {
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<code goes here>
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}
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%}
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...
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Output
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------
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<span class="graphviz" style="text-align: center;"><img src="data:image/png;base64,_BASE64_IMAGE DATA_/></span>
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"""
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import base64
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import re
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from errno import EINVAL, EPIPE
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from .mdx_liquid_tags import LiquidTags
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SYNTAX = '{% dot graphviz [program] [dot code] %}'
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DOT_BLOCK_RE = re.compile(r'^\s*(?P<program>\w+)\s*\{\s*(?P<code>.*\})\s*\}$', re.MULTILINE | re.DOTALL)
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def run_graphviz(program, code, options=[], format='png'):
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""" Runs graphviz programs and returns image data
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Copied from https://github.com/tkf/ipython-hierarchymagic/blob/master/hierarchymagic.py
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"""
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import os
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from subprocess import Popen, PIPE
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dot_args = [program] + options + ['-T', format]
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if os.name == 'nt':
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# Avoid opening shell window.
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# * https://github.com/tkf/ipython-hierarchymagic/issues/1
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# * http://stackoverflow.com/a/2935727/727827
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p = Popen(dot_args, stdout=PIPE, stdin=PIPE, stderr=PIPE, creationflags=0x08000000)
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else:
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p = Popen(dot_args, stdout=PIPE, stdin=PIPE, stderr=PIPE)
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wentwrong = False
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try:
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# Graphviz may close standard input when an error occurs,
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# resulting in a broken pipe on communicate()
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stdout, stderr = p.communicate(code.encode('utf-8'))
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except (OSError, IOError) as err:
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if err.errno != EPIPE:
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raise
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wentwrong = True
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except IOError as err:
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if err.errno != EINVAL:
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raise
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wentwrong = True
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if wentwrong:
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# in this case, read the standard output and standard error streams
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# directly, to get the error message(s)
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stdout, stderr = p.stdout.read(), p.stderr.read()
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p.wait()
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if p.returncode != 0:
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raise RuntimeError('dot exited with error:\n[stderr]\n{0}'.format(stderr.decode('utf-8')))
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return stdout
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@LiquidTags.register('graphviz')
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def graphviz_parser(preprocessor, tag, markup):
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""" Simple Graphviz parser """
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# Parse the markup string
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m = DOT_BLOCK_RE.search(markup)
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if m:
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# Get program and DOT code
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code = m.group('code')
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program = m.group('program').strip()
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# Run specified program with our markup
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output = run_graphviz(program, code)
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# Return Base64 encoded image
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return '<span class="graphviz" style="text-align: center;"><img src="data:image/png;base64,%s"></span>' % base64.b64encode(output).decode('utf-8')
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else:
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raise ValueError('Error processing input. '
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'Expected syntax: {0}'.format(SYNTAX))
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#----------------------------------------------------------------------
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# This import allows image tag to be a Pelican plugin
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from .liquid_tags import register
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