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Marco BARNIG edited this page Jan 13, 2020 · 23 revisions

In the present tutorial lesson 11 we will develop our second Orthanc plugin for our RadioLogicArchive. The C++ code is contained in the file MicroPlugin.cpp, saved in the folder /OrthancPlugins/MicroPlugin/ in the present repository.

If we compare the code with the NanoPlugin code we discover the following changes:

  • the line OrthancPlugins::RegisterRestCallback<Moien>("/moien", true);

has been replaced with

OrthancPluginRegisterOnStoredInstanceCallback(context, ScaleDicomImage);

  • the short callback function void Moien()

has been replaced with a large callback function OrthancPluginErrorCode ScaleDicomImage().

This callback function is called when a new instance has been stored. The function provides the data and ID of this instance and writes it to a temporary folder:

OrthancPluginErrorCode writeError = OrthancPluginWriteFile()

The instance is decompressed with a system call to the gdcmconvexecutable of the GDCM library.

std::string gdcmconvCommand = "/GDCM-3.0.3-Linux-x86_64/bin/gdcmconv --raw /tmp/original.dcm /tmp/raw.dcm";
int dcmscaleStatus = system(dcmscaleCommand.c_str());

In a next step the instance is downscaled with a system call to the dcmscale excutable of the DCMTK library.

std::string dcmscaleCommand = "/dcmtk-3.6.4-linux-x86_64-static/bin/dcmscale +Sxf 0.5 /tmp/raw.dcm /tmp/scaled.dcm";  
int dcmscaleStatus = system(dcmscaleCommand.c_str());

The modified instance is read from the temporary folder

OrthancPluginErrorCode readError = OrthancPluginReadFile

and restored to the server:

OrthancPluginErrorCode storeError = OrthancPluginRestApiPost()

If an error (read, write, store, ...) happens during the process, the callback function returns with the related error-code. If the process terminates well, the memory buffers are freed and the temporary files are removed. The callback function returns with a success message.

If we compile this code, no issue will be raised, but if we run the code, the plugin will turn in an endless loop. When the modified instance is uploaded to the server, the OnStoredInstanceCallbackis called again, and the whole scaling process is repeated. The image gets smaller and smaller and the process will probably stop once, due to a miscalculation.

To prevent the plugin from entering a loop, we check the origin of the callback call at the beginning of the function with the statement

if (OrthancPluginGetInstanceOrigin(context, instance) == OrthancPluginInstanceOrigin_Plugin) {return OrthancPluginErrorCode_Success;}

If the origin is the plugin, we stop the process and return the callback function.

If we compare the CMakeLists.txt file and the Resources folder we don't find any changes, except the project name.

You probably wonder how the gdcmconv and dcmscale executables are popping up in the Docker container. Short answer: we must install them. Here comes the recipe:

  1. run a new development container

In lesson 10 we learned how to create a development container. We use the same procedure for the MicroPlugin.

docker container run -it --name RadioLogicDevelopment dev-snapshot /bin/bash

  1. install DCMTK
cd /    
wget ftp://dicom.offis.de/pub/dicom/offis/software/dcmtk/dcmtk364/bin/dcmtk-3.6.4-linux-x86_64-static.tar.bz2               
tar -xvjf dcmtk-3.6.4-linux-x86_64-static.tar.bz2    
rm -r dcmtk-3.6.4-linux-x86_64-static.tar.bz2  
chmod -R 777 dcmtk-3.6.4-linux-x86_64-static
  1. install GDCM
wget https://github.com/malaterre/GDCM/releases/download/v3.0.3/GDCM-3.0.3-Linux-x86_64.tar.gz       
tar xvzf GDCM-3.0.3-Linux-x86_64.tar.gz   
rm -r GDCM-3.0.3-Linux-x86_64.tar.gz  
chmod -R 777 GDCM-3.0.3-Linux-x86_64

Meanwhile we know how to build a plugin inside a Docker container. The next figure shows that building the MicroPlugin is also a success story.

microplugin-build

We know also how to commit an image with the embedded DCMTK and GDCM libraries, how to copy the MiniPlugin into the plugins folder and how to run a new RadioLogicArchive container from this image. Feel free to go back to earlier lessons if you are not sure what to do. If the container is running, you can upload a DICOM instance with a HTTP POST request to scale the image to half-size. Here is the curl command to send a file to the archive:

curl -u username:password -X POST https://<orthanc-ip-address:8042>/instances/ --data-binary @test.dcm

microplugin-curl

When the RadioLogicArchive is run in verbose mode we should see the following information:

microplugin-logs

In the All patients webpage two instances have been added with the same Patient-, Study- and Series-UID. The first instance contains the original image, the second the down-scaled image. The following figures show the related DICOM tags.

original-echography

scaled-echography

A preview displays the scaled image.

echography

In the next lesson we will add more complexity to the plugin which gets a promotion from micro to mini.

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