JBIGTest

1//
2// Copyright (c) 2001-2020 by PDFTron Systems Inc. All Rights Reserved.
3//
4
5using System;
6using System.IO;
7using System.Threading.Tasks;
8using Windows.Foundation;
9
10using pdftron.PDF;
11using pdftron.SDF;
12
13using pdftron.Common;
14using PDFNetUniversalSamples.ViewModels;
15using pdftron.Filters;
16using Windows.Storage.Streams;
17
18namespace PDFNetSamples
19{
20    /// <summary>
21    /// This sample project illustrates how to recompress bi-tonal images in an 
22    /// existing PDF document using JBIG2 compression. The sample is not intended 
23    /// to be a generic PDF optimization tool.
24    ///
25    /// Also a sample page compressed using CCITT Fax compression is located under 
26    /// 'PDFNet/Samples/TestFiles' folder.
27    /// </summary>
28    class JBIG2Test : Sample
29    {
30        private string FILE_NAME = "US061222892-a.pdf";
31
32        public JBIG2Test() :
33            base("JBIG2", "This sample recompress bi-tonal images in an existing PDF document using JBIG2 compression.")
34        { }
35
36        public override IAsyncAction RunAsync()
37        {
38            return Task.Run(new System.Action(async () =>
39           {
40               WriteLine("--------------------------------");
41               WriteLine("Starting JBIG2 Compression Test...");
42               WriteLine("--------------------------------\n");
43
44               PDFDoc pdf_doc = new PDFDoc(Path.Combine(InputPath, FILE_NAME));
45               pdf_doc.InitSecurityHandler();
46
47               SDFDoc cos_doc = pdf_doc.GetSDFDoc();
48
49               int num_objs = cos_doc.XRefSize();
50
51               // Loop through all cross reference table objects
52               for (int i = 1; i < num_objs; ++i)
53               {
54                   Obj obj = cos_doc.GetObj(i);
55                   if (obj != null && !obj.IsFree() && obj.IsStream())
56                   {
57                       // Process only images
58                       DictIterator itr = obj.Find("Subtype");
59                       if (!itr.HasNext() || itr.Value().GetName() != "Image")
60                           continue;
61
62                       pdftron.PDF.Image input_image = new pdftron.PDF.Image(obj);
63                       pdftron.PDF.Image new_image = null;
64
65                       // Process only gray-scale images
66                       if (input_image.GetComponentNum() != 1)
67                           continue;
68
69                       int bpc = input_image.GetBitsPerComponent();
70                       if (bpc != 1) // Recompress 1 BPC images
71                           continue;
72
73                       // Skip images that are already compressed using JBIG2
74                       itr = obj.Find("Filter");
75                       if (itr.HasNext() && itr.Value().IsName() &&
76                           itr.Value().GetName() == "JBIG2Decode")
77                           continue;
78
79                       FilterReader reader = new FilterReader(obj.GetDecodedStream());
80
81                       ObjSet hint_set = new ObjSet();
82
83                       Obj hint = hint_set.CreateArray();
84                       hint.PushBackName("JBIG2");
85                       hint.PushBackName("Lossless");
86                       hint.PushBackName("Threshold");
87                       hint.PushBackNumber(0.4);
88                       hint.PushBackName("SharePages");
89                       hint.PushBackNumber(10000);
90
91                       new_image = pdftron.PDF.Image.Create(
92                           cos_doc,
93                           reader,
94                           input_image.GetImageWidth(),
95                           input_image.GetImageHeight(),
96                           1,
97                           ColorSpace.CreateDeviceGray(),
98                           hint);
99
100                       Obj new_img_obj = new_image.GetSDFObj();
101
102                       // Copy any important entries from the image dictionary
103                       itr = obj.Find("ImageMask");
104                       if (itr.HasNext()) new_img_obj.Put("ImageMask", itr.Value());
105
106                       itr = obj.Find("Mask");
107                       if (itr.HasNext()) new_img_obj.Put("Mask", itr.Value());
108
109                       cos_doc.Swap(i, new_image.GetSDFObj().GetObjNum());
110                   }
111               }
112
113               await pdf_doc.SaveAsync(Path.Combine(OutputPath, FILE_NAME), SDFDocSaveOptions.e_remove_unused).AsTask().ConfigureAwait(false);
114
115               WriteLine("Saved " + Path.Combine(OutputPath, FILE_NAME));
116
117               await AddFileToOutputList(Path.Combine(OutputPath, FILE_NAME));
118
119               WriteLine("--------------------------------");
120               WriteLine("Done JBIG2 Compression Test.");
121               WriteLine("--------------------------------\n");
122
123           })).AsAsyncAction();
124        }
125    }
126}