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Add parallel processing to OCR text extraction of full documents #124

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1f1ec93
Add parallel processing to OCR text extraction
Dec 18, 2014
7427d08
Add Parallel installation to documentation
Dec 18, 2014
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5 changes: 5 additions & 0 deletions index.html
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Original file line number Diff line number Diff line change
Expand Up @@ -159,6 +159,11 @@ <h2 id="installation">Installation &amp; Dependencies</h2>
<tt>aptitude install libreoffice</tt><br />
On the Mac, download and install <a href="http://www.libreoffice.org/download">the latest release</a>.
</li>
<li>
(Optional) Install <a href="http://www.gnu.org/software/parallel/">Parallel</a>:<br>
<tt>[aptitude | port | brew] install parallel</tt><br>
Parallel speeds up OCR text extraction of documents by processing pages in parallel.
</li>
</ol>

<p><i>
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8 changes: 4 additions & 4 deletions lib/docsplit.rb
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Expand Up @@ -13,11 +13,11 @@ module Docsplit
ESCAPED_ROOT = ESCAPE[ROOT]

METADATA_KEYS = [:author, :date, :creator, :keywords, :producer, :subject, :title, :length]

GM_FORMATS = ["image/gif", "image/jpeg", "image/png", "image/x-ms-bmp", "image/svg+xml", "image/tiff", "image/x-portable-bitmap", "application/postscript", "image/x-portable-pixmap"]

DEPENDENCIES = {:java => false, :gm => false, :pdftotext => false, :pdftk => false, :pdftailor => false, :tesseract => false, :osd => false}
GM_FORMATS = ["image/gif", "image/jpeg", "image/png", "image/x-ms-bmp", "image/svg+xml", "image/tiff", "image/x-portable-bitmap", "application/postscript", "image/x-portable-pixmap"]

DEPENDENCIES = {:java => false, :gm => false, :pdftotext => false, :pdftk => false, :pdftailor => false, :tesseract => false, :osd => false, :parallel => false}

# Check for all dependencies, and note their absence.
dirs = ENV['PATH'].split(File::PATH_SEPARATOR)
DEPENDENCIES.each_key do |dep|
Expand Down Expand Up @@ -75,7 +75,7 @@ def self.extract_#{key}(pdfs, opts={})
end
EOS
end

def self.extract_info(pdfs, opts={})
pdfs = ensure_pdfs(pdfs)
InfoExtractor.new.extract_all(pdfs, opts)
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18 changes: 11 additions & 7 deletions lib/docsplit/text_extractor.rb
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Expand Up @@ -72,18 +72,22 @@ def extract_from_ocr(pdf, pages)
FileUtils.remove_entry_secure tiff
end
else
tiff = "#{tempdir}/#{@pdf_name}.tif"
escaped_tiff = ESCAPE[tiff]
run "MAGICK_TMPDIR=#{tempdir} OMP_NUM_THREADS=2 gm convert -despeckle #{MEMORY_ARGS} #{OCR_FLAGS} #{escaped_pdf} #{escaped_tiff} 2>&1"
#if the user says don't do orientation detection or the plugin is not installed, set psm to 0
run "tesseract #{escaped_tiff} #{base_path} -l #{@language} #{psm} 2>&1"
clean_text(base_path + '.txt') if @clean_ocr
if DEPENDENCIES[:parallel]
run "MAGICK_TMPDIR=#{tempdir} gm convert -despeckle +adjoin #{MEMORY_ARGS} #{OCR_FLAGS} #{escaped_pdf} #{tempdir}/page_%d.tiff 2>&1"
run "parallel tesseract -l #{@language} #{psm} {} {.} ::: #{tempdir}/page_*.tiff 2>&1"
run "cat #{tempdir}/page_*.txt >'#{base_path}.txt' 2>&1"
else
tiff = "#{tempdir}/#{@pdf_name}.tif"
escaped_tiff = ESCAPE[tiff]
run "MAGICK_TMPDIR=#{tempdir} OMP_NUM_THREADS=2 gm convert -despeckle #{MEMORY_ARGS} #{OCR_FLAGS} #{escaped_pdf} #{escaped_tiff} 2>&1"
run "tesseract #{escaped_tiff} #{base_path} -l #{@language} #{psm} 2>&1"
end
clean_text("#{base_path}.txt") if @clean_ocr
end
ensure
FileUtils.remove_entry_secure tempdir if File.exists?(tempdir)
end


private

def clean_text(file)
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