seed points[, which positions are displayed to them as colored circles,]{} to properly indicate their inclusion into the set of object or background representatives. New seeds can be added at the position of [current]{} interaction via a long-press on the overlay image. The segmentation result as well as [the]{} displayed contour line adapt accordingly after each interaction.[]{data-label="fig:joint_prototype"}](images/joint_segmentation_prototype_contrast.png){width="\columnwidth" height="0.61296534017\columnwidth"}

![The approximated influence map for new seed point locations [for the joint segmentation prototype]{}. The map is generated by a weighted sum of gradient magnitude image, number of cell changes [$h_e^{t=\infty}$ per cell $e$]{} obtained from [the]{} previous segmentation, [as well as the]{} distance to the contour line of the current segmentation. []{data-label="fig:joint_prototype_prob_map"}](images/prob_map_1.png){height="0.61296534017\columnwidth"}

Questionnaires {#sec:questionnaires}
--------------

### System Usability Scale () {#sec:questionnaires_sus}

The  [@brooke1996sus; @lewis2009factor] is a widely used, reliable, and low-cost survey to assess the overall usability of a prototype, product, or service [@kortum2013usability]. Its focus is on pragmatic quality evaluation [@ISO92411998; @ISO92412018]. The survey is technology agnostic, which enables a utilization of the usability of many types of user interfaces and  [@bangor2009determining]. The questionnaire consists of ten statements and an unipolar five-point Likert scale [@likert1932technique]. This allows for an assessment in a time span of about three minutes per participant. 