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Detect language only on one page of PDF

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To detect the language currently the entire document gets processed. If
a different language has been detected than the default one, the entire
document will be processed again for the new language.

This PR analyzes the middle page for its language and either processes
the remaining pages with the default language if it didn't differ, or
processes all pages for the new guessed language.

The amount of processed pages comes down from the worst case `2n` to
worst case `n+1`.
This commit is contained in:
Pit Kleyersburg 2016-02-14 16:13:34 +01:00
parent 9162e41507
commit aeab9a0e81
1 changed files with 16 additions and 1 deletions

17
src/documents/consumer.py

@ -9,6 +9,7 @@ import random
import re import re
import subprocess import subprocess
import math
import pyocr import pyocr
from PIL import Image from PIL import Image
@ -152,9 +153,14 @@ class Consumer(Renderable):
simple language detection trial & error. simple language detection trial & error.
""" """
if not pngs:
raise OCRError
self._render(" OCRing the document", 2) self._render(" OCRing the document", 2)
raw_text = self._ocr(pngs, self.DEFAULT_OCR_LANGUAGE) # Since the division gets rounded down by int, this calculation works for every edge-case, i.e. 1
middle = int(len(pngs) / 2)
raw_text = self._ocr([pngs[middle]], self.DEFAULT_OCR_LANGUAGE)
guessed_language = self._guess_language(raw_text) guessed_language = self._guess_language(raw_text)
@ -166,10 +172,14 @@ class Consumer(Renderable):
"with what we have.", "with what we have.",
1 1
) )
raw_text = self._ocr(pngs[:middle], self.DEFAULT_OCR_LANGUAGE) + raw_text
raw_text += self._ocr(pngs[middle+1:], self.DEFAULT_OCR_LANGUAGE)
return raw_text return raw_text
raise OCRError raise OCRError
if ISO639[guessed_language] == self.DEFAULT_OCR_LANGUAGE: if ISO639[guessed_language] == self.DEFAULT_OCR_LANGUAGE:
raw_text = self._ocr(pngs[:middle], self.DEFAULT_OCR_LANGUAGE) + raw_text
raw_text += self._ocr(pngs[middle+1:], self.DEFAULT_OCR_LANGUAGE)
return raw_text return raw_text
try: try:
@ -183,6 +193,8 @@ class Consumer(Renderable):
), ),
0 0
) )
raw_text = self._ocr(pngs[:middle], self.DEFAULT_OCR_LANGUAGE) + raw_text
raw_text += self._ocr(pngs[middle+1:], self.DEFAULT_OCR_LANGUAGE)
return raw_text return raw_text
raise OCRError raise OCRError
@ -191,6 +203,9 @@ class Consumer(Renderable):
Performs a single OCR attempt. Performs a single OCR attempt.
""" """
if not pngs:
return ""
self._render(" Parsing for {}".format(lang), 2) self._render(" Parsing for {}".format(lang), 2)
with Pool(processes=self.THREADS) as pool: with Pool(processes=self.THREADS) as pool: