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Robot users for the evaluation of boundary-tracking approaches in interactive image segmentation

Recent advances in interactive image segmentation focused on eliminating the user bias during evaluation by simulating their behavior using robot users. However, these robots only work for region-based methods, excluding the important class of approaches that rely on the boundary-tracking paradigm. We propose completely novel robot users that are able to simulate the human user behavior when segmenting an image through the addition of anchor points close to the object's boundary. Our robots constantly evaluate the optimum-boundary segment being computed from a previously selected anchor point to the current virtual mouse position, seeking for the longest possible segment with minimum acceptable error. A new anchor is added when the error is too high and the robots iterate until closing the contour, just like real users. We validate our robots by conducting a user study and extensive experiments, considering two boundary-tracking methods: live-wire-on-the-fly and Riverbed. We further show how our robot users can be used to assess hybrid approaches that combine boundary-tracking with region-based delineation, such as LiveMarkers, while conjecturing that robots might lead to new methods for automatic foreground segmentation.