Module: PdfExtract::Chunks

Defined in:
lib/model/chunks.rb

Class Method Summary collapse

Class Method Details

.include_in(pdf) ⇒ Object 



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# File 'lib/model/chunks.rb', line 26

def self.include_in pdf

  pdf.spatials :chunks, :paged => true, :depends_on => [:characters] do |parser|
    rows = {}

    parser.before do
      rows = {}
    end

    parser.objects :characters do |chars|
      y = chars[:y]
      rows[y] = [] if rows[y].nil?

      idx = rows[y].index { |obj| chars[:x] <= obj[:x] }
      if idx.nil?
        rows[y] << chars.dup
      else
        rows[y].insert idx, chars.dup
      end
    end

    parser.after do
      char_slop = pdf.settings[:char_slop]
      word_slop = pdf.settings[:word_slop]
      overlap_slop = pdf.settings[:overlap_slop]

      text_chunks = []

      rows.each_pair do |y, row|
        char_width = row.first[:width]

        while row.length > 1
          left = row.first
          right = row[1]

          if (left[:x] + left[:width] + (char_width * char_slop)) >= right[:x]
            # join as adjacent chars
            row[0] = Spatial.merge left, right
            row.delete_at 1
            char_width = right[:width] unless right[:content].strip =~ /[^A-Za-z0-9]/
          elsif (left[:x] + left[:width] + (char_width * word_slop)) >= right[:x]
            # join with a ' ' in the middle.
            row[0] = Spatial.merge left, right, :separator => ' '
            row.delete_at 1
            char_width = right[:width] unless right[:content].strip =~ /[^A-Za-z0-9]/
          else
            # leave 'em be.
            text_chunks << left
            row.delete_at 0
            char_width = row.first[:width]
          end
        end

        text_chunks << row.first
      end

      # Merge chunks that have slightly different :y positions but which
      # mostly overlap in the y dimension.

      text_chunks.sort_by! { |obj| obj[:x] }
      merged_text_chunks = []

      while text_chunks.count > 1
        left = text_chunks.first
        right = text_chunks[1]

        overlap = [left[:height], right[:height]].min - (left[:y] - right[:y]).abs
        overlap = overlap / [left[:height], right[:height]].min

        if overlap >= overlap_slop
          # TODO follow char / word slop rules.
          # join
          text_chunks[0] = Spatial.merge left, right
          text_chunks.delete_at 1
        else
          # no join
          merged_text_chunks << text_chunks.first
          text_chunks.delete_at 0
        end
      end

      merged_text_chunks << text_chunks.first

      # Remove empty lines - they mess up region detection by
      # making them join together.
      merged_text_chunks.reject { |chunk| chunk[:content].strip == "" }
    end
  end
end