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#!/usr/bin/env python
"""Extract text from ocropus outputs.
This concatenates the individual text fragments, from left to right and then
top to bottom.
It orders the fragments by y-midpoint, then uses x coordinates to order
overlapping fragments.
Input is an hOCR file (from ocropus-hocr).
Output is text, printed to stdout.
import re
import sys
from bs4 import BeautifulSoup
def overlapping(a, b):
"""Two lines are overlapping if >50% of either is in the other."""
overlap = min(a['y2'], b['y2']) - max(a['y1'], b['y1'])
height = min(a['y2'] - a['y1'], b['y2'] - b['y1'])
return 1.0 * overlap / height > 0.5
def sort_lines(lines):
lines = lines[:]
# First, sort by y-midpoint
lines.sort(key=lambda line: (line['y1'] + line['y2']) * 0.5)
# If a line is entirely to the left of the one preceding it, and they
# overlap vertically, then they're out of order.
i = 0
while i < len(lines) - 1:
a = lines[i]
b = lines[i + 1]
if b['x2'] < a['x1'] and overlapping(a, b):
lines[i], lines[i + 1] = b, a
i = 0
i += 1
for a, b in zip(lines[:-1], lines[1:]):
if overlapping(a, b):
b['continuation'] = True
return lines
def hocr_to_lines(hocr_path):
lines = []
soup = BeautifulSoup(file(hocr_path))
for tag in'.ocr_line'):
m = re.match(r'bbox (-?\d+) (-?\d+) (-?\d+) (-?\d+)', tag.get('title'))
assert m
x0, y0, x1, y1 = (int(v) for v in m.groups())
'text': tag.text,
'x1': x0,
'y1': y1,
'x2': x1,
'y2': y0 # note swap
# hOCR specifies that y-coordinates are from the bottom.
# We fix that here. We don't know the height of the image, so we use the
# largest y-value in its place.
h = max(line['y1'] for line in lines)
for line in lines:
line['y1'] = h - line['y1']
line['y2'] = h - line['y2']
return lines
if __name__ == '__main__':
_, hocr_path = sys.argv
lines = hocr_to_lines(hocr_path)
lines = sort_lines(lines)
output = ''
for idx, line in enumerate(lines):
if idx > 0:
if line.get('continuation'):
output += ' '
output += '\n'
if 'text' in line:
output += line['text']
print output