The mask defines the area where the automatic detection takes place. It is useful to digitize dotted or dashed lines:
You can also add a rectangular region to the mask by selecting
(⌘B). To erase some part of the mask, selection . To clear the whole mask at once, select .The brush size can be changed from the window toolbar or from the Detection). Select to add or remove the item from the toolbar.
(⌘,) window (underIf the curve you try to digitize is too jittery, the curve detection algorithms may fail to "follow" the line, even if you try to change the tolerance value. In this case, you should use a mask together with the horizontal curve detection algorithm (⌘3), which then detects one point per abscissa, instead of following the curve.