Ruby use OCR to make searchable PDFs and extract text

#---------------------------------------------------------------------------------------
# Copyright (c) 2001-2023 by Apryse Software Inc. All Rights Reserved.
# Consult LICENSE.txt regarding license information.
#---------------------------------------------------------------------------------------

require '../../../PDFNetC/Lib/PDFNetRuby'
include PDFNetRuby
require '../../LicenseKey/RUBY/LicenseKey'

$stdout.sync = true

# Relative path to the folder containing test files.
input_path =  "../../TestFiles/OCR/"
output_path = "../../TestFiles/Output/"

#---------------------------------------------------------------------------------------
# The following sample illustrates how to use OCR module
#---------------------------------------------------------------------------------------

	# The first step in every application using PDFNet is to initialize the 
	# library and set the path to common PDF resources. The library is usually 
	# initialized only once, but calling Initialize multiple times is also fine.
	PDFNet.Initialize(PDFTronLicense.Key)
	
	# The location of the OCR Module
        PDFNet.AddResourceSearchPath("../../../PDFNetC/Lib/");
	
	#Example 1) Convert the first page to PNG and TIFF at 92 DPI.
	
	begin  
		if !OCRModule.IsModuleAvailable

			puts 'Unable to run OCRTest: PDFTron SDK OCR module not available.'
			puts '---------------------------------------------------------------'
			puts 'The OCR module is an optional add-on, available for download'
			puts 'at http://www.pdftron.com/. If you have already downloaded this'
			puts 'module, ensure that the SDK is able to find the required files'
			puts 'using the PDFNet::AddResourceSearchPath() function.'

		else

			# Example 1) Process image without specifying options, default language - English - is used
			# --------------------------------------------------------------------------------

			# A) Setup empty destination doc
			doc = PDFDoc.new
	
			# B) Run OCR on the .png with options

			OCRModule.ImageToPDF(doc, input_path + "psychomachia_excerpt.png", nil)

			# C) Check the result

			doc.Save(output_path + "psychomachia_excerpt.pdf", 0)
			puts "Example 1: psychomachia_excerpt.png"

			doc.Close

			# Example 2) Process document using multiple languages
			# --------------------------------------------------------------------------------

			# A) Setup empty destination doc

			doc = PDFDoc.new

			# B) Setup options with multiple target languages, English will always be considered as secondary language

			opts = OCROptions.new
			opts.AddLang("rus")
			opts.AddLang("deu")

			# C) Run OCR on the .jpg with options

			OCRModule.ImageToPDF(doc, input_path + "multi_lang.jpg", opts)

			# D) Check the result

			doc.Save(output_path + "multi_lang.pdf", 0)
			puts "Example 2: multi_lang.jpg"

			doc.Close

			# Example 3) Process a .pdf specifying a language - German - and ignore zone comprising a sidebar image
			# --------------------------------------------------------------------------------

			# A) Open the .pdf document


			doc = PDFDoc.new(input_path + "german_kids_song.pdf")

			# B) Setup options with a single language and an ignore zone

			opts = OCROptions.new
			opts.AddLang("deu")

			ignore_zones = RectCollection.new
			ignore_zones.AddRect(Rect.new(424, 163, 493, 730))
			opts.AddIgnoreZonesForPage(ignore_zones, 1)

			# C) Run OCR on the .pdf with options

			OCRModule.ProcessPDF(doc, nil)

			# D) check the result

			doc.Save(output_path + "german_kids_song.pdf", 0)
			puts "Example 3: german_kids_song.pdf"

			doc.Close

			# Example 4) Process multi-page tiff with text/ignore zones specified for each page,
			# optionally provide English as the target language
			# --------------------------------------------------------------------------------

			# A) Setup empty destination doc

			doc = PDFDoc.new

			# B) Setup options with a single language plus text/ignore zones

			opts = OCROptions.new
			opts.AddLang("eng")

			ignore_zones = RectCollection.new

			# ignore signature box in the first 2 pages
			ignore_zones.AddRect(Rect.new(1492, 56, 2236, 432))
			opts.AddIgnoreZonesForPage(ignore_zones, 1)

			opts.AddIgnoreZonesForPage(ignore_zones, 2)

			# can use a combination of ignore and text boxes to focus on the page area of interest,
			# as ignore boxes are applied first, we remove the arrows before selecting part of the diagram
			ignore_zones.Clear
			ignore_zones.AddRect(Rect.new(992, 1276, 1368, 1372))
			opts.AddIgnoreZonesForPage(ignore_zones, 3)

			text_zones = RectCollection.new
			# we only have text zones selected in page 3

			# select horizontal BUFFER ZONE sign
			text_zones.AddRect(Rect.new(900, 2384, 1236, 2480))

			# select right vertical BUFFER ZONE sign
			text_zones.AddRect(Rect.new(1960, 1976, 2016, 2296))
			# select Lot No.
			text_zones.AddRect(Rect.new(696, 1028, 1196, 1128))

			# select part of the plan inside the BUFFER ZONE
			text_zones.AddRect(Rect.new(428, 1484, 1784, 2344))
			text_zones.AddRect(Rect.new(948, 1288, 1672, 1476))
			opts.AddTextZonesForPage(text_zones, 3)

			# C) Run OCR on the .pdf with options

			OCRModule.ImageToPDF(doc, input_path + "bc_environment_protection.tif", opts)

			# D) check the result

			doc.Save(output_path + "bc_environment_protection.pdf", 0)
			puts "Example 4: bc_environment_protection.tif"

			doc.Close

			# Example 5) Alternative workflow for extracting OCR result JSON, postprocessing
			# (e.g., removing words not in the dictionary or filtering special
			# out special characters), and finally applying modified OCR JSON to the source PDF document
			# --------------------------------------------------------------------------------

			# A) Open the .pdf document

			doc = PDFDoc.new(input_path + "zero_value_test_no_text.pdf")

			# B) Run OCR on the .pdf with default English language

			json = OCRModule.GetOCRJsonFromPDF(doc, nil)

			# C) Post-processing step (whatever it might be)

			puts "Have OCR result JSON, re-applying to PDF"

			OCRModule.ApplyOCRJsonToPDF(doc, json)

			# D) Check the result

			doc.Save(output_path + "zero_value_test_no_text.pdf", 0)
			puts "Example 5: extracting and applying OCR JSON from zero_value_test_no_text.pdf"

			doc.Close

			# Example 6) The postprocessing workflow has also an option of extracting OCR results in XML format,
			# similar to the one used by TextExtractor
			# --------------------------------------------------------------------------------

			# A) Setup empty destination doc

			doc = PDFDoc.new

			# B) Run OCR on the .tif with default English language, extracting OCR results in XML format. Note that
			# in the process we convert the source image into PDF.
			# We reuse this PDF document later to add hidden text layer to it.

			xml = OCRModule.GetOCRXmlFromImage(doc, input_path + "physics.tif", nil)

			# C) Post-processing step (whatever it might be)

			puts "Have OCR result XML, re-applying to PDF"

			OCRModule.ApplyOCRXmlToPDF(doc, xml)

			# D) Check the result

			doc.Save(output_path + "physics.pdf", 0)
			puts "Example 6: extracting and applying OCR XML from physics.tif"

			doc.Close


			# Example 7) Resolution can be manually set, when DPI missing from metadata or is wrong
			# --------------------------------------------------------------------------------

			# A) Setup empty destination doc

			doc = PDFDoc.new

			# B) Setup options with a text zone

			opts = OCROptions.new
			text_zones = RectCollection.new
			text_zones.AddRect(Rect.new(140, 870, 310, 920))
			opts.AddIgnoreZonesForPage(text_zones, 1)

			# C) Manually override DPI

			opts.AddDPI(100)

			# D) Run OCR on the .jpg with options

			OCRModule.ImageToPDF(doc, input_path + "corrupted_dpi.jpg", opts)

                        # E) Check the result

			doc.Save(output_path + "corrupted_dpi.pdf", 0)
			puts "Example 7: converting image with corrupted resolution metadata corrupted_dpi.jpg to pdf with searchable text"

			doc.Close

			end
	rescue Exception=>e
		puts e

	end
	PDFNet.Terminate