criterion for the interactive image partitioning. The transparency of both, the contour line and seed mask displayed, is adjustable to one of five fixed values via the *opacity* toggle button. The image contrast and brightness (windowing) can be adapted with standard control sliders for the window width and the window center operating on the image intensity value range [@jin2001contrast]. All protoypes incorporate a *help* button used to provide additional guidance for the prototype’s usage during the segmentation task. The segmentation process starts with a set of pre-defined background-labels $\mathbf{S}^0$ along the edges of the image, since an object is assumed to be located in its entirety inside the displayed region of the image.

###  Segmentation Prototype {#sec:semi-manual_prototype}

The of the prototype, depicted in **Fig.**\[fig:semi-manual\_prototype\], provides several interaction elements. A user can add seed points as an overlay mask displayed on top of the image. These seed points have a pre-defined label of either for the object or used for all other image elements. The label of the next brush strokes (scribbles) can be altered via the buttons named and . After each interaction , a new iteration of the seeded segmentation is started given the image $\mathbf{I}$ as well as 