125 lines
3.5 KiB
Ruby
125 lines
3.5 KiB
Ruby
# coding: utf-8
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# typed: strict
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# frozen_string_literal: true
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require 'pdf/reader/overlapping_runs_filter'
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require 'pdf/reader/zero_width_runs_filter'
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class PDF::Reader
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# Takes a collection of TextRun objects and renders them into a single
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# string that best approximates the way they'd appear on a render PDF page.
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#
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# media box should be a 4 number array that describes the dimensions of the
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# page to be rendered as described by the page's MediaBox attribute
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class PageLayout
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DEFAULT_FONT_SIZE = 12
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def initialize(runs, mediabox)
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# mediabox is a 4-element array for now, but it'd be nice to switch to a
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# PDF::Reader::Rectangle at some point
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PDF::Reader::Error.validate_not_nil(mediabox, "mediabox")
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@mediabox = process_mediabox(mediabox)
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@runs = runs
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@mean_font_size = mean(@runs.map(&:font_size)) || DEFAULT_FONT_SIZE
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@mean_font_size = DEFAULT_FONT_SIZE if @mean_font_size == 0
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@median_glyph_width = median(@runs.map(&:mean_character_width)) || 0
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@x_offset = @runs.map(&:x).sort.first || 0
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lowest_y = @runs.map(&:y).sort.first || 0
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@y_offset = lowest_y > 0 ? 0 : lowest_y
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end
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def to_s
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return "" if @runs.empty?
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return "" if row_count == 0
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page = row_count.times.map { |i| " " * col_count }
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@runs.each do |run|
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x_pos = ((run.x - @x_offset) / col_multiplier).round
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y_pos = row_count - ((run.y - @y_offset) / row_multiplier).round
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if y_pos <= row_count && y_pos >= 0 && x_pos <= col_count && x_pos >= 0
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local_string_insert(page[y_pos-1], run.text, x_pos)
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end
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end
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interesting_rows(page).map(&:rstrip).join("\n")
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end
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private
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def page_width
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@mediabox.width
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end
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def page_height
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@mediabox.height
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end
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# given an array of strings, return a new array with empty rows from the
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# beginning and end removed.
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#
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# interesting_rows([ "", "one", "two", "" ])
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# => [ "one", "two" ]
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#
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def interesting_rows(rows)
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line_lengths = rows.map { |l| l.strip.length }
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return [] if line_lengths.all?(&:zero?)
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first_line_with_text = line_lengths.index { |l| l > 0 }
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last_line_with_text = line_lengths.size - line_lengths.reverse.index { |l| l > 0 }
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interesting_line_count = last_line_with_text - first_line_with_text
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rows[first_line_with_text, interesting_line_count].map
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end
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def row_count
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@row_count ||= (page_height / @mean_font_size).floor
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end
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def col_count
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@col_count ||= ((page_width / @median_glyph_width) * 1.05).floor
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end
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def row_multiplier
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@row_multiplier ||= page_height.to_f / row_count.to_f
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end
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def col_multiplier
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@col_multiplier ||= page_width.to_f / col_count.to_f
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end
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def mean(collection)
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if collection.size == 0
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0
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else
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collection.inject(0) { |accum, v| accum + v} / collection.size.to_f
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end
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end
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def median(collection)
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if collection.size == 0
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0
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else
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collection.sort[(collection.size * 0.5).floor]
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end
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end
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def local_string_insert(haystack, needle, index)
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haystack[Range.new(index, index + needle.length - 1)] = String.new(needle)
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end
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def process_mediabox(mediabox)
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if mediabox.is_a?(Array)
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msg = "Passing the mediabox to PageLayout as an Array is deprecated," +
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" please use a Rectangle instead"
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$stderr.puts msg
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PDF::Reader::Rectangle.from_array(mediabox)
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else
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mediabox
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end
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end
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end
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end
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