This plugin was developed as a part of Google Summer of Code project with KDE. The plugin has additional functionalities of HDR image generation on the existing Expoblending plugin in digiKam that blends stack of bracketed images.
For building the plugin, you need the entire digiKam package available in https://projects.kde.org/projects/extragear/graphics/kipi-plugins/repository. Clone the source codes in the master branch. Just add the source codes of this repository into the extra/kipi-plugins directory, update CmakeLists.txt with this plugin path and build the entire digiKam package.
A more detailed description is given here: http://www.digikam.org/contrib
For any issues regarding the plugin, please feel free to contact me.
Overview: https://community.kde.org/GSoC/2013/StatusReports#Soumajyoti_Sarkar