< Android samples

JBIG2Test - Java

The sample project illustrates how to recompress bi-tonal (black and white) images in existing PDF documents using JBIG2 compression. The sample is intended to show how to specify hint information for image encoder and is not meant to be a generic PDF optimization tool. PDFNet supports both loss-less and lossy JBIG2 compression. To give you a feeling of compression rates possible with PDFNet we re-compressed a document containing 17 scanned pages. The original input document is ~1.4MB and is using standard CCITT Fax compression. Loss-less JBIG2 compression shrunk down the file to 641KB. Lossy JBIG2 compression shrunk down the file to 176KB.

//---------------------------------------------------------------------------------------
// Copyright (c) 2001-2018 by PDFTron Systems Inc. All Rights Reserved.
// Consult legal.txt regarding legal and license information.
//---------------------------------------------------------------------------------------

import com.pdftron.filters.Filter;
import com.pdftron.filters.FilterReader;
import com.pdftron.pdf.*;
import com.pdftron.sdf.DictIterator;
import com.pdftron.sdf.Obj;
import com.pdftron.sdf.ObjSet;
import com.pdftron.sdf.SDFDoc;

// This sample project illustrates how to recompress bi-tonal images in an 
// existing PDF document using JBIG2 compression. The sample is not intended 
// to be a generic PDF optimization tool.
//
// You can download the entire document using the following link:
//   http://www.pdftron.com/net/samplecode/data/US061222892.pdf
public class JBIG2Test 
{

	public static void main(String[] args) 
	{
		PDFNet.initialize();

		try 
		{
			PDFDoc pdf_doc=new PDFDoc("../../TestFiles/US061222892-a.pdf");
			pdf_doc.initSecurityHandler();

			SDFDoc cos_doc = pdf_doc.getSDFDoc();
			int num_objs = (int)cos_doc.xRefSize();
			for(int i=1; i<num_objs; ++i) 
			{
				Obj obj = cos_doc.getObj(i);
				if(obj!=null  && !obj.isFree()  && obj.isStream()) 
				{
					// Process only images
					DictIterator itr = obj.find("Subtype");
					if(!itr.hasNext() || !itr.value().getName().equals("Image"))
						continue;
					
					Image input_image=new Image(obj);
					// Process only gray-scale images
					if(input_image.getComponentNum() != 1)
						continue;
					int bpc = input_image.getBitsPerComponent();
					if(bpc != 1)	// Recompress only 1 BPC images
						continue;

					// Skip images that are already compressed using JBIG2
					itr = obj.find("Filter");
					if (itr.hasNext()  && itr.value().isName()  && 
						!itr.value().getName().equals("JBIG2Decode")) continue; 

					Filter filter=obj.getDecodedStream();
					FilterReader reader=new FilterReader(filter);

					ObjSet hint_set=new ObjSet(); 
					Obj hint=hint_set.createArray(); // A hint to image encoder to use JBIG2 compression
					hint.pushBackName("JBIG2");
					hint.pushBackName("Lossless");

					Image new_image = Image.create(cos_doc, reader, 
						input_image.getImageWidth(), 
						input_image.getImageHeight(), 1, ColorSpace.createDeviceGray(), hint);

					Obj new_img_obj = new_image.getSDFObj();
					itr = obj.find("Decode");
					if(itr.hasNext())
						new_img_obj.put("Decode", itr.value());
					itr = obj.find("ImageMask");
					if (itr.hasNext())
						new_img_obj.put("ImageMask", itr.value());
					itr = obj.find("Mask");
					if (itr.hasNext())
						new_img_obj.put("Mask", itr.value());

					cos_doc.swap(i, new_img_obj.getObjNum());
				}
			}

			pdf_doc.save("../../TestFiles/Output/US061222892_JBIG2.pdf", SDFDoc.SaveMode.REMOVE_UNUSED, null);
			pdf_doc.close();
		}
		catch(Exception e)
		{
			e.printStackTrace();
		}

		PDFNet.terminate();
	}

}