Orthanc Web Viewer plugin¶

Compilation¶

The procedure to compile this plugin is similar of that for the core of Orthanc. The following commands should work for most UNIX-like distribution (including GNU/Linux):

$ mkdir Build
$ cd Build
$ cmake .. -DSTATIC_BUILD=ON -DCMAKE_BUILD_TYPE=Release
$ make

The compilation will produce a shared library OrthancWebViewer that contains the Web viewer plugin. Pre-compiled binaries for Microsoft Windows are also available.

Remark: Some older build instructions are also available in the source distribution.

Usage¶

You of course first have to install Orthanc. Once Orthanc is installed, you must change the configuration file to tell Orthanc where it can find the plugin: This is done by properly modifying the Plugins option. You could for instance use the following configuration file:

{
  "Name" : "MyOrthanc",
  [...]
  "Plugins" : [
    "/home/user/OrthancWebViewer/Build/libOrthancWebViewer.so"
  ]
}

Orthanc must of course be restarted after the modification of its configuration file. The log will contain an output similar to:

# Orthanc ./Configuration.json
W0226 16:59:10.480226  7906 main.cpp:636] Orthanc version: mainline
[...]
W0226 16:59:10.519664  7906 PluginsManager.cpp:258] Registering plugin 'web-viewer' (version 1.0)
W0226 16:59:10.519696  7906 PluginsManager.cpp:148] Initializing the Web viewer
W0226 16:59:10.520004  7906 PluginsManager.cpp:148] Web viewer using 6 threads for the decoding of the DICOM images
W0226 16:59:10.520021  7906 PluginsManager.cpp:148] Storing the cache of the Web viewer in folder: OrthancStorage/WebViewerCache
W0226 16:59:10.522011  7906 PluginsManager.cpp:148] Web viewer using a cache of 100 MB
[...]
W0226 16:59:10.530807  7906 main.cpp:516] HTTP server listening on port: 8042
W0226 16:59:10.581029  7906 main.cpp:526] DICOM server listening on port: 4242
W0226 16:59:10.581066  7906 main.cpp:533] Orthanc has started

Once a DICOM series is opened using Orthanc Explorer, a yellow button entitled Orthanc Web Viewer will show up. It will open the Web viewer for that particular series. See also the demonstration video on official homepage of the plugin.

Advanced options¶

The configuration of the Web viewer can be fine-tuned by adding some options:

{
  "Name" : "MyOrthanc",
  [...]
  "Plugins" : [
    "/home/user/OrthancWebViewer/Build/libOrthancWebViewer.so"
  ],
  "WebViewer" : {
    "CachePath" : "WebViewerCache",
    "CacheSize" : 10,
    "Threads" : 4
  }
}

• CachePath specifies the location of the cache of the Web viewer. By default, the cache is located inside the storage directory of Orthanc.
• CacheSize specifies the maximum size for the cached images, in megabytes. By default, a cache of 100 MB is used.
• Threads specifies the number of threads that are used by the plugin to decode the DICOM images.

Old advanced options (up to 2.5)¶

Up to release 2.5 of the Orthanc Web Viewer plugin, the plugin was shipping a decoder of DICOM images using the GDCM library. In May 2020, the support of GDCM has been moved as a separate plugin. As a consequence, releases <= 2.5 had two more advanced options, that were removed starting with version 2.6:

• EnableGdcm specified whether GDCM should be used to decode DICOM images, replacing the built-in decoder of Orthanc that internally uses DCMTK. This was notably necessary to deal with DICOM images encoded using JPEG2000, as this format is not readily supported by the core version of DCMTK. By default, this option was set to true.
• As a complement to the EnableGdcm option, it was also possible to restrict the GDCM decoder to some specific transfer syntaxes using the RestrictTransferSyntaxes option.

For instance, the following configuration would enable GDCM to decode JPEG 2000 images, while using DCMTK to decode the other transfer syntaxes:

{
  [...]
  "WebViewer" : {
    "EnableGdcm" : true,
    "RestrictTransferSyntaxes" : [
      "1.2.840.10008.1.2.4.90",   // JPEG 2000 Image Compression (Lossless Only)
      "1.2.840.10008.1.2.4.91",   // JPEG 2000 Image Compression
      "1.2.840.10008.1.2.4.92",   // JPEG 2000 Part 2 Multicomponent Image Compression (Lossless Only)
      "1.2.840.10008.1.2.4.93"    // JPEG 2000 Part 2 Multicomponent Image Compression
    ]
  }
}

Frequently Asked Questions¶

• If Orthanc does not start anymore after a hard shutdown, this might reflect a corruption in the cache of the Web viewer. In such a case, it is safe to remove the folder that contains the cache. By default, this folder is called OrthancStorage/WebViewerCache/. Of course, don’t remove the folder OrthancStorage/, as it contains the DICOM files.