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class OCRSDK::PDF < OCRSDK::Image
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# We're on a shaky ground regarding what kind of pdfs
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# should be recognized and what shouldn't.
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# Currently we count that if there are
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# images * 20 > length of text
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# then this document might need recognition.
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# Assumption is that there might be a title,
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# page numbers or credits along with images.
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def recognizeable?
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reader = PDF::Reader.new @image_path
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images = 0
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text = 0
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chars = Set.new
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reader.pages.each do |page|
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text += page.text.length
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chars += page.text.split('').map(&:ord).uniq
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images += page.xobjects.map {|k, v| v.hash[:Subtype]}.count(:Image)
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end
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# count number of distinct characters
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# in case of "searchable", but incorrectly recognized document
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images * 20 > text || chars.length < 10
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rescue PDF::Reader::MalformedPDFError, PDF::Reader::UnsupportedFeatureError
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false
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end
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end
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