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PDF Image Extraction in Ruby

Sample Ruby code for using PDFTron SDK to extract images from PDF files, along with their positioning information and DPI. Instead of converting PDF images to a Bitmap, you can also extract uncompressed/compressed image data directly using element.GetImageData() (described in the PDF Data Extraction code sample). Learn more about our PDF Parsing & Content Extraction Library.

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Step 2: Add the code:

#---------------------------------------------------------------------------------------
# Copyright (c) 2001-2019 by PDFTron Systems Inc. All Rights Reserved.
# Consult LICENSE.txt regarding license information.
#---------------------------------------------------------------------------------------

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

$stdout.sync = true

#-----------------------------------------------------------------------------------
# This sample illustrates one approach to PDF image extraction 
# using PDFNet.
# 
# Note: Besides direct image export, you can also convert PDF images 
# to GDI+ Bitmap, or extract uncompressed/compressed image data directly 
# using element.GetImageData() (e.g. as illustrated in ElementReaderAdv 
# sample project).
#-----------------------------------------------------------------------------------

$image_counter = 0

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

def ImageExtract(reader)
	element = reader.Next()
	while !(element.nil?) do
		if (element.GetType() == Element::E_image or
			element.GetType() == Element::E_inline_image)

			$image_counter =$image_counter + 1
			puts "--> Image: " + $image_counter.to_s()
			puts "Width: " + element.GetImageWidth().to_s()
			puts "Height: " + element.GetImageHeight().to_s()
			puts "BPC: " + element.GetBitsPerComponent().to_s()
			
			ctm = element.GetCTM()
			x2 = 1
			y2 = 1
			pt = Point.new(x2, y2)
			point = ctm.Mult(pt)
			puts "Coords: x1=" + ctm.m_h.to_s() + ", y1=" + ctm.m_v.to_s() + ", x2=" + point.x.to_s() + ", y2=" + point.y.to_s()
			
			if element.GetType() == Element::E_image
				image = Image.new(element.GetXObject())
				
				fname = "image_extract1_" + $image_counter.to_s()
				
				path = $output_path + fname
				image.Export(path)
				
				#path = $output_path + fname + ".tif"
				#image.ExportAsTiff(path)
				
				#path = $output_path + fname + ".png"
				#image.ExportAsPng(path)
			end
		elsif element.GetType() == Element::E_form
			reader.FormBegin()
			ImageExtract(reader)
			reader.End()	
		end		
		element = reader.Next()
	end
end

	# Initialize PDFNet
	PDFNet.Initialize()	
	
	# Example 1: 
	# Extract images by traversing the display list for 
	# every page. With this approach it is possible to obtain 
	# image positioning information and DPI.
	
	doc = PDFDoc.new($input_path + "newsletter.pdf")
	doc.InitSecurityHandler()
	
	reader = ElementReader.new()
	
	# Read every page
	itr = doc.GetPageIterator()
	while itr.HasNext() do
		reader.Begin(itr.Current())
		ImageExtract(reader)
		reader.End()
		itr.Next()
	end

	doc.Close()

	puts "Done."	
	puts "----------------------------------------------------------------"
	
	# Example 2: 
	# Extract images by scanning the low-level document.
	
	doc = PDFDoc.new($input_path + "newsletter.pdf")
	doc.InitSecurityHandler()
	$image_counter= 0
	
	cos_doc = doc.GetSDFDoc()
	num_objs = cos_doc.XRefSize()
	i = 1
	while i < num_objs do
		obj = cos_doc.GetObj(i)

		if !(obj.nil?) and !(obj.IsFree()) and obj.IsStream()
			# Process only images
			itr = obj.Find("Type")

			if !(itr.HasNext()) or !(itr.Value().GetName() == "XObject")
				i = i + 1
				next
			end
			
			itr = obj.Find("Subtype")
			if !(itr.HasNext()) or !(itr.Value().GetName() == "Image")
				i = i + 1
				next
			end
			
			image = Image.new(obj)
			$image_counter = $image_counter + 1
			puts "-. Image: " + $image_counter.to_s()
			puts "Width: " + image.GetImageWidth().to_s()
			puts "Height: " + image.GetImageHeight().to_s()
			puts "BPC: " + image.GetBitsPerComponent().to_s()
			
			fname = "image_extract2_" + $image_counter.to_s()
				
			path = $output_path + fname
			image.Export(path)
			
			#path = $output_path + fname + ".tif"
			#image.ExportAsTiff(path)
			
			#path = $output_path + fname + ".png"
			#image.ExportAsPng(path)
		end
		i = i + 1
	end
	doc.Close()