Parser and converter for jupyter markdown cells for nbconvert

embedimages.py

"""HTML Image handling for embedded images in markdown cells."""

#-----------------------------------------------------------------------------
# Copyright (c) 2013, the IPython Development Team.
#
# Distributed under the terms of the Modified BSD License.
#
# The full license is in the file COPYING.txt, distributed with this software.
#-----------------------------------------------------------------------------

#-----------------------------------------------------------------------------
# Imports
#-----------------------------------------------------------------------------
from ipython_genutils.py3compat import PY3
if PY3:
    from html.parser import HTMLParser
else:
    from HTMLParser import HTMLParser
import base64
import os.path

#-----------------------------------------------------------------------------
# Functions
#-----------------------------------------------------------------------------

__all__ = ['img2base64']


def img2base64(s):
    """Parse HTML image references in Markdown cells.

    This looks for HTML tags having a img tag name `img`
    and converts the image to a data URI for static embedding.
    The tranformation looks like this:

    `<img src="./Images/My_image.png" width="800" height="800" alt="Alt_name" title="Mytitle" align="center" />`

    Becomes

    `<img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADIA..." width="800" height="800" alt="Alt_name" title="Mytitle" align="center" />`

    Any HTML tag can be used, which allows the citations to be formatted
    in HTML in any manner.
    """
    parser = Img2Base64Parser()
    parser.feed(s)
    parser.close()
    outtext = u''
    startpos = 0
    for img in parser.imglist:
            outtext += s[startpos:img[1][0]]
            outtext += 'data:image/%s;base64,%s'% \
                (img[0][1],str(img[0][0]).lstrip('b\'').rstrip('\''))
            startpos = img[1][1] if len(img)==3 else -1
    outtext += s[startpos:] if startpos != -1 else ''
    return outtext

#-----------------------------------------------------------------------------
# Classes
#-----------------------------------------------------------------------------

class Img2Base64Parser(HTMLParser):
    """Image Parser
    Replaces html img file references with base64 encoded strings.
    
    Inherites from HTMLParser, overrides:
     - handle_starttag
     - handle_endtag
    """
    # number of open tags
    opentags = None
    # list of found imgs
    imglist = None
    # active img tag
    imgtag = None

    def __init__(self):
        self.imglist = []
        self.opentags = 0
        HTMLParser.__init__(self)
    
    def get_offset(self):
        # Compute startposition in source
        lin, offset = self.getpos()
        pos = 0
        for i in range(lin):
            pos = self.data.find('src=',pos) + 5
        return pos
        
    def handle_starttag(self, tag, attrs):
        # for each tag check if attributes are present and convert src to base64
        if self.opentags == 0 and len(attrs)>0:
            for atr, data in attrs:
                if atr.lower() == 'src':
                    self.imgtag = tag
                    self.opentags = 1
                    print(len(data))
                    with open(data, "rb") as image_file:
                        encoded_data = base64.b64encode(image_file.read())
                        extension = os.path.splitext(data)[1][1:].strip().lower()
                    self.imglist.append([[encoded_data, extension],
                                         [self.get_offset(), self.get_offset()+len(data)]])
                    return
                
        if tag == self.imgtag:
            # found an open img tag but not the starting one  
            self.opentags += 1
  
    def handle_endtag(self, tag):
        if tag == self.imgtag:
            # found img tag check if starting one
            if self.opentags == 1:
                pos = self.get_offset()
                self.imglist[-1].append(pos+len(tag)+ 3)
            self.opentags -= 1
        
    def feed(self, data):
        self.data = data
        HTMLParser.feed(self, data)