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1 .. _gdcm:
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2
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3
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4 GDCM plugin for Orthanc
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5 =======================
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6
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7 .. contents::
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8
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9 This **official** plugin extends Orthanc with a decoder/transcoder of
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10 DICOM images that takes advantage of the `Grassroots GDCM library
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11 <https://en.wikipedia.org/wiki/GDCM>`__.
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12
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13 This plugin notably replaces the built-in decoder/transcoder of
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14 Orthanc that internally uses `DCMTK
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15 <https://dicom.offis.de/dcmtk.php.en>`__. This is notably necessary to
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16 deal with DICOM images encoded using `JPEG2000
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17 <https://en.wikipedia.org/wiki/JPEG_2000>`__, as this format is not
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18 readily supported by the core version of DCMTK.
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19
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20
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21 History
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22 -------
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23
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24 Originally, this plugin was a sample snippet that was shipped with the
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25 source code of Orthanc versions below 1.7.0, in the folder
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26 ``Plugins/Samples/GdcmDecoder/``. This sample code was itself bundled
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27 in the :ref:`Orthanc Web viewer <webviewer>` (up to release 2.5) and
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28 in the :ref:`Osimis Web viewer <osimis_webviewer>` plugins (up to
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29 releases 1.3.x).
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30
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31 In May 2020, starting with Orthanc 1.7.0, as a part of the large
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32 refactoring necessary to implement :ref:`transcoding <transcoding>`,
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33 the GDCM plugin was migrated as separate plugin. The reasons are
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34 twofold:
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35
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36 * To avoid redundancies between the two viewers, and to improve
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37 performance by avoiding multiple calls to GDCM on unsupported DICOM
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38 instances.
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39
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40 * To uncouple the viewers and the :ref:`DICOMweb <dicomweb>` plugins
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41 from the dependency on GDCM. This notably allows to more easily
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42 follow new releases of the GDCM library.
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43
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44
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45 Compilation
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46 -----------
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47
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48 .. highlight:: bash
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49
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50 The procedure to compile this plugin is similar of that for the
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51 :ref:`core of Orthanc <binaries>`. The following commands should work
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52 for most UNIX-like distribution (including GNU/Linux)::
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53
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54 $ mkdir Build
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55 $ cd Build
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56 $ cmake .. -DSTATIC_BUILD=ON -DCMAKE_BUILD_TYPE=Release
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57 $ make
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58
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59 The compilation will produce a shared library ``OrthancGdcm`` that
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60 contains the GDCM decoder/transcoder plugin. Pre-compiled binaries for
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61 Microsoft Windows `are also available
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62 <https://www.orthanc-server.com/browse.php?path=/plugin-gdcm>`__.
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63
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64 *Remark:* Some older build instructions are also available in the
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65 `source distribution
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66 <https://hg.orthanc-server.com/orthanc-gdcm/file/default/Resources/BuildInstructions.txt>`__.
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67
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68
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69 Usage
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70 -----
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71
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72 .. highlight:: json
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73
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74 You of course first have to :ref:`install Orthanc <compiling>`. Once
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75 Orthanc is installed, you must change the :ref:`configuration file
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76 <configuration>` to tell Orthanc where it can find the plugin: This is
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77 done by properly modifying the ``Plugins`` option. You could for
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78 instance use the following configuration file::
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79
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80 {
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81 "Name" : "MyOrthanc",
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82 [...]
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83 "Plugins" : [
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84 "/home/user/OrthancGdcm/Build/libOrthancGdcm.so"
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85 ]
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86 }
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87
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88 .. highlight:: text
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89
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90 Orthanc must of course be restarted after the modification of its
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91 configuration file. Carefully inspect the :ref:`logs <log>` to make
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92 sure that the GDCM plugin is properly loaded.
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93
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94
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95 Advanced options
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96 ----------------
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97
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98 .. highlight:: json
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99
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100 The configuration of the GDCM plugin can be fine-tuned by adding some options::
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101
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102 {
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103 "Name" : "MyOrthanc",
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104 [...]
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105 "Plugins" : [
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106 "/home/user/OrthancGdcm/Build/libOrthancGdcm.so"
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107 ],
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108 "Gdcm" : {
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109 "Enable" : false,
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110 "Throttling" : 4
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111 },
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112 "BuiltinDecoderTranscoderOrder" : "After"
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113 }
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114
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115 * ``Enable`` specifies whether the GDCM decoder/transcoder is enabled.
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116 By default, this option is set to ``true``.
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117
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118 * ``Throttling`` specifies the maximum number of threads that can
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119 simultaneously call the GDCM decoder/transcoder. This is useful to
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120 avoid uncontrolled CPU or RAM usage if many people are connected to
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121 the same Orthanc server. By default, no throttling is applied, and
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122 an unrestricted number of threads can call GDCM simultaneously.
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123
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415
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124 * Starting with Orthanc 1.7.0, ``BuiltinDecoderTranscoderOrder`` is a
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125 configuration option of the Orthanc core (i.e. outside of the
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126 ``Gdcm`` section) that can be used to control whether the built-in
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127 DCMTK decoder/transcoder is applied before or after GDCM.
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128
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129 As a complement to the ``Enable`` option, you also have the
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130 possibility to restrict the GDCM decoder/transcoder to some specific
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131 `transfer syntaxes
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132 <http://dicom.nema.org/medical/dicom/current/output/html/part05.html#chapter_10>`__
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133 using the ``RestrictTransferSyntaxes`` option. For instance, the
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134 following configuration would use GDCM to decode JPEG 2000 images,
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135 while using DCMTK to decode the other transfer syntaxes::
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136
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137 {
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138 [...]
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139 "Gdcm" : {
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140 "Enable" : true,
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141 "RestrictTransferSyntaxes" : [
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142 "1.2.840.10008.1.2.4.90", // JPEG 2000 Image Compression (Lossless Only)
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143 "1.2.840.10008.1.2.4.91", // JPEG 2000 Image Compression
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144 "1.2.840.10008.1.2.4.92", // JPEG 2000 Part 2 Multicomponent Image Compression (Lossless Only)
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145 "1.2.840.10008.1.2.4.93" // JPEG 2000 Part 2 Multicomponent Image Compression
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146 ]
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147 }
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148 }
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