Added the first text parser backend (PDF) and updated the requirements files and README

apps/ocr/parsers/__init__.py

@@ -0,0 +1,40 @@
+import codecs
+import os
+import subprocess
+import tempfile
+import sys
+
+import slate
+
+from django.utils.translation import ugettext as _
+
+from ocr.parsers.exceptions import ParserError, ParserUnknownFile
+
+mimetype_registry = {}
+
+
+def register_parser(mimetype, function):
+    mimetype_registry[mimetype] = {'function': function}
+
+
+def pdf_parser(document_page):
+    fd = document_page.document.open()
+    pdf_pages = slate.PDF(fd)
+    fd.close()
+    
+    if pdf_pages[document_page.page_number - 1] == '\x0c':
+        raise ParserError
+    
+    document_page.content = pdf_pages[document_page.page_number - 1]
+    document_page.page_label = _(u'Text extracted from PDF')
+    document_page.save()
+       
+
+def parse_document_page(document_page):
+    try:
+        mimetype_registry[document_page.document.file_mimetype]['function'](document_page)
+    except KeyError:
+        raise ParserUnknownFile
+
+        
+register_parser('application/pdf', pdf_parser)

apps/ocr/parsers/exceptions.py

@@ -0,0 +1,10 @@
+class ParserError(Exception):
+    """
+    Raised when a text parser fails to understand a file it been passed
+    or the resulting parsed text is invalid
+    """
+    pass
+
+
+class ParserUnknownFile(Exception):
+    pass