Trace curve mode

To trace points on a curve in your graph, you must make sure you are in Trace curve mode. You can select Trace curve mode from the Edit menu, or from the mode selection in the top left of the window. When clicking on or near a line, the point will automatically snap to the line. The point can be moved around using Ctrl in combination with the arrow keys, while selected.

You can only enter Trace curve mode if your axes have been defined.

You can trace both solid and dashed curves. To start tracing, select a first point on the line. Then select the last point on the line. ScanIt will find the shortest route connecting the points, while traveling over lines.

tracing a curve

Make sure the scan window size is set appropriately. The scan window size (in pixels) should capture the significant features of the image (such as line thickness and distance between parts of dotted or dashes lines). Choosing the window size too small may cause ScanIt to fail to find connections between dotted or dashed lines. Choosing the window size too large may cause ScanIt to not see the line at all, or take steps that are too big. Change the window size to update the route along the line.

ScanIt may not immediately find a route along the desired line, but take a short cut along some other line(s) in your image. To prevent ScanIt from taking a shortcut in a wrong direction, select the line direction in the top of the window (e.g. positive X direction will prevent steps being taken in a negative X direction).

Click more points along the missed parts of the line to correct the trace. Adding a point in a regions of sharp curvature is advised, such as at the top of the curve in this image.

tracing a curve

Click on the accept button will move the found points into a new data set (the current data set will be used if empty).

The specified trace points will show as square symbols on your screen; additionally found points are shown using cross symbols. Selected specified points appear in another color than unselected data points (see options). You can select and manipulate your specified points.

Press Ctrl+L to toggle connecting your data points with lines.