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pypdfocr_pdf.py
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pypdfocr_pdf.py
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#!/usr/bin/env python2.7
# Copyright 2013 Virantha Ekanayake All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# Following code is adapted and modified from hocr-pdf.py released under
# Apache License, Version 2.0 available at
# https://code.google.com/p/hocr-tools/source/browse/hocr-pdf
# - Code was improved to allow multi-page hocr files
"""
Wrap pdf generation and text addition code
"""
from optparse import OptionParser
import sys, os
import re
import logging
import shutil
import time
import tempfile
import glob
import cStringIO
import base64
import zlib
import math
# Pkg to read multiple image tiffs
from PIL import Image
from reportlab.pdfgen.canvas import Canvas
from reportlab.pdfbase import pdfmetrics
from reportlab.pdfbase.ttfonts import TTFont
from xml.etree.ElementTree import ElementTree, ParseError
import xml.etree
# Import Pypdf2
from PyPDF2 import PdfFileMerger, PdfFileReader, PdfFileWriter, utils
class PyPdf(object):
"""Class to create pdfs from images"""
def __init__(self, gs):
self.load_invisible_font()
self.gs = gs # Pointer to ghostscript object
pass
def mergeRotateAroundPointPage(self,page, page2, rotation, tx, ty):
# Code taken from here:
# http://stackoverflow.com/questions/6041244/how-to-merge-two-landscape-pdf-pages-using-pypdf/17392824#17392824
# Unclear why PyPDF2 builtin page rotation functions don't work
translation = [[1, 0, 0],
[0, 1, 0],
[-tx,-ty,1]]
rotation = math.radians(rotation)
rotating = [[math.cos(rotation), math.sin(rotation),0],
[-math.sin(rotation),math.cos(rotation), 0],
[0, 0, 1]]
rtranslation = [[1, 0, 0],
[0, 1, 0],
[tx,ty,1]]
ctm = utils.matrixMultiply(translation, rotating)
ctm = utils.matrixMultiply(ctm, rtranslation)
return page.mergeTransformedPage(page2, [ctm[0][0], ctm[0][1],
ctm[1][0], ctm[1][1],
ctm[2][0], ctm[2][1]])
def overlay_hocr_pages(self, dpi, hocr_filenames, orig_pdf_filename):
logging.debug("Going to overlay following files onto %s" % orig_pdf_filename)
# Sort the hocr_filenames into natural keys!
hocr_filenames.sort(key=lambda x: self.natural_keys(x[0] ))
logging.debug(hocr_filenames)
pdf_dir, pdf_basename = os.path.split(orig_pdf_filename)
basename = os.path.splitext(pdf_basename)[0]
pdf_filename = os.path.join(pdf_dir, "%s_ocr.pdf" % (basename))
text_pdf_filenames = []
for img_filename, hocr_filename in hocr_filenames:
text_pdf_filename = self.overlay_hocr_page(dpi, hocr_filename, img_filename)
logging.info("Created temp OCR'ed pdf containing only the text as %s" % (text_pdf_filename))
text_pdf_filenames.append(text_pdf_filename)
writer = PdfFileWriter()
orig = open(orig_pdf_filename, 'rb')
for orig_pg, text_pg_filename in zip(self.iter_pdf_page(orig), text_pdf_filenames):
text_file = open(text_pg_filename, 'rb')
text_pg = self.iter_pdf_page(text_file).next()
orig_rotation_angle = int(orig_pg.get('/Rotate', 0))
if orig_rotation_angle != 0:
logging.info("Original Rotation: %s" % orig_pg.get("/Rotate", 0))
self.mergeRotateAroundPointPage(orig_pg, text_pg, orig_rotation_angle, text_pg.mediaBox.getWidth()/2, text_pg.mediaBox.getWidth()/2)
# None of these commands worked for me:
#orig_pg.rotateCounterClockwise(orig_rotation_angle)
#orig_pg.mergeRotatedPage(text_pg,text_rotation_angle)
else:
orig_pg.mergePage(text_pg)
orig_pg.compressContentStreams()
writer.addPage(orig_pg)
with open(pdf_filename, 'wb') as f:
# Flush out this page merge so we can close the text_file
writer.write(f)
text_file.close()
orig.close()
for fn in text_pdf_filenames:
os.remove(fn)
logging.info("Created OCR'ed pdf as %s" % (pdf_filename))
return pdf_filename
def _get_img_dims(self, img_filename):
"""
:rval: (width, height, dpi)
"""
img = Image.open(img_filename)
w,h = img.size
dpi = img.info['dpi']
width = w*72.0/dpi[0]
height = h*72.0/dpi[1]
del img
return (width, height, dpi)
def overlay_hocr_page(self, dpi, hocr_filename, img_filename):
hocr_dir, hocr_basename = os.path.split(hocr_filename)
img_dir, img_basename = os.path.split(img_filename)
logging.debug("hocr_filename:%s, hocr_dir:%s, hocr_basename:%s" % (hocr_filename, hocr_dir, hocr_basename))
assert(img_dir == hocr_dir)
#basename = hocr_basename.split('.')[0]
basename = os.path.splitext(hocr_basename)[0]
pdf_filename = os.path.join("text_%s_ocr.pdf" % (basename))
# Switch to the hocr directory to make this easier
cwd = os.getcwd()
if hocr_dir != "":
os.chdir(hocr_dir)
with open(pdf_filename, "wb") as f:
logging.info("Overlaying hocr and creating text pdf %s" % pdf_filename)
pdf = Canvas(f, pageCompression=1)
pdf.setCreator('pypdfocr')
pdf.setTitle(os.path.basename(hocr_filename))
pdf.setPageCompression(1)
width, height, dpi_jpg = self._get_img_dims(img_basename)
pdf.setPageSize((width,height))
logging.info("Page width=%f, height=%f" % (width, height))
pg_num = 1
logging.info("Adding text to page %s" % pdf_filename)
self.add_text_layer(pdf,hocr_basename,pg_num,height,dpi)
pdf.showPage()
pdf.save()
os.chdir(cwd)
return os.path.join(hocr_dir, pdf_filename)
def iter_pdf_page(self, f):
reader = PdfFileReader(f)
for pgnum in range(reader.getNumPages()):
pg = reader.getPage(pgnum)
yield pg
def _atoi(self,text):
return int(text) if text.isdigit() else text
def natural_keys(self, text):
'''
alist.sort(key=natural_keys) sorts in human order
http://nedbatchelder.com/blog/200712/human_sorting.html
(See Toothy's implementation in the comments)
'''
return [ self._atoi(c) for c in re.split('(\d+)', text) ]
def add_text_layer(self,pdf, hocrfile, page_num,height, dpi):
"""Draw an invisible text layer for OCR data"""
p1 = re.compile('bbox((\s+\d+){4})')
p2 = re.compile('baseline((\s+[\d\.\-]+){2})')
hocr = ElementTree()
hocr.parse(hocrfile)
logging.debug(xml.etree.ElementTree.tostring(hocr.getroot()))
for c in hocr.getroot(): # Find the <body> tag
if c.tag != 'body':
continue
for page in c: # Each child in the body is a page tag
if (page.attrib['class'] != "ocr_page"):
assert ("Why is this hocr not paging properly??")
if page.attrib['id'] == 'page_%d' %(page_num):
break
for line in page.findall(".//{http://www.w3.org/1999/xhtml}span"):
#for line in page.findall(".//span"):
if line.attrib['class'] != 'ocr_line':
continue
linebox = p1.search(line.attrib['title']).group(1).split()
try:
baseline = p2.search(line.attrib['title']).group(1).split()
except AttributeError:
baseline = [ 0, 0 ]
linebox = [float(i) for i in linebox]
baseline = [float(i) for i in baseline]
for word in line:
if word.attrib['class'] != 'ocrx_word':
continue
word_text = []
for child in word.iter():
if child.text:
word_text.append(child.text)
word.text = ' '.join(word_text)
logging.debug(word.text)
#for child in word:
#if child.tag:
#word.text = child.text
if word.text is None:
continue
font_width = pdf.stringWidth(word.text.strip(), 'invisible', 8)
if font_width <= 0:
continue
box = p1.search(word.attrib['title']).group(1).split()
box = [float(i) for i in box]
b = self.polyval(baseline, (box[0] + box[2]) / 2 - linebox[0]) + linebox[3]
text = pdf.beginText()
text.setTextRenderMode(3) # double invisible
text.setFont('invisible', 8)
text.setTextOrigin(box[0] * 72 / dpi, height - b * 72 / dpi)
box_width = (box[2] - box[0]) * 72 / dpi
text.setHorizScale(100.0 * box_width / font_width)
text.textLine(word.text.strip())
#logging.debug( "Pg%s: %s" % (page_num,word.text.strip()))
pdf.drawText(text)
def polyval(self,poly, x):
return x * poly[0] + poly[1]
# Glyphless variation of vedaal's invisible font retrieved from
# http://www.angelfire.com/pr/pgpf/if.html, which says:
# 'Invisible font' is unrestricted freeware. Enjoy, Improve, Distribute freely
def load_invisible_font(self):
font = """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"""
ttf = cStringIO.StringIO(zlib.decompress(base64.decodestring(font)))
pdfmetrics.registerFont(TTFont('invisible', ttf))