The resulting bounding boxes signify the buttons that would
be visible to a human being. We have not performed a thorough
evaluation of the accuracy of our technique but the results are
good in the cases we have examined. Figure 2 presents some
cases related to ads as well as other views. We note that this
technique depends only on computer graphics algorithms, is
completely black box as it does not even need to extract the UI
hierarchy from the system. It can therefore be generally used
for any widget whose internals are opaque to the UI hierarchy
extraction.