NijiGPen is an add-on that expands Blender's Grease Pencil capabilities for 2D graphic design and illustration workflows. It introduces core 2D vector operations, enabling boolean functions like union, difference, and intersection, as well as shape offset and inset calculations. The tool also provides methods for converting 2D Grease Pencil shapes into 3D meshes, supporting frustum and contour generation alongside planar geometry with auto-generated normal maps.

Additional utilities focus on workflow efficiency and external asset integration. The tool features automatic line sketch cleanup and the ability to extract line art or flat colors from imported images. For cross-application workflows, NijiGPen provides enhanced clipboard support for SVG code and XML palettes, allows Photoshop brush import, and enables direct PSD file exports.