< Linux samples

JBIG2Test - PHP

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.

<?php
//---------------------------------------------------------------------------------------
// Copyright (c) 2001-2018 by PDFTron Systems Inc. All Rights Reserved.
// Consult LICENSE.txt regarding license information.
//---------------------------------------------------------------------------------------
include("../../../PDFNetC/Lib/PDFNetPHP.php");

// Relative path to the folder containing the test files.
$input_path = getcwd()."/../../TestFiles/";
$output_path = $input_path."Output/";

// 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

	PDFNet::Initialize();

	$pdf_doc = new PDFDoc("../../TestFiles/US061222892-a.pdf") ;
	$pdf_doc->InitSecurityHandler();

	$cos_doc = $pdf_doc->GetSDFDoc();
	$num_objs = $cos_doc->XRefSize();
	for($i = 1; $i < $num_objs; ++$i) 
	{
		$obj = $cos_doc->GetObj($i);
		if($obj  && !$obj->IsFree()  && $obj->IsStream()) 
		{
			// Process only images
			$itr = $obj->Find("Subtype");
			if(!$itr->HasNext() || $itr->Value()->GetName() != "Image")
				continue;
			
			$input_image = new Image($obj);
			// Process only gray-scale images
			if($input_image->GetComponentNum() != 1)
				continue;
			$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() == "JBIG2Decode") continue; 

			$filter=$obj->GetDecodedStream();
			$reader = new FilterReader($filter);


			$hint_set = new ObjSet(); 	// A hint to image encoder to use JBIG2 compression
			$hint=$hint_set->CreateArray();
			
			$hint->PushBackName("JBIG2");
			$hint->PushBackName("Lossless");

			$new_image = Image::Create($cos_doc, $reader, 
				$input_image->GetImageWidth(), 
				$input_image->GetImageHeight(), 1, ColorSpace::CreateDeviceGray(), $hint);

			$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::e_remove_unused);
	$pdf_doc->Close();

	echo "Done.";
?>