# Polygon and Freehand Contour Drawing Tool

Use this tool to trace 2D contours on image slices.

### Drawing polygonal contours

You can draw a polygon by making a sequence of left-clicks with the mouse over the image slice. When you want to close the polygon, right-click.

### Drawing freehand contours

To draw a freehand segment, hold the left mouse button down and drag the mouse. To finish drawing the segment, release the left mouse button. You can combine freehand segments with polygon segments. To close the contour, right-click.

### Controlling freehand behavior

In the 'Tool Options' panel, you can control how freehand drawing behaves. Select between continuous drawing, which gives you greatest control, but makes subsequent editing most difficult, and line segment mode, where the freehand contour is build up from straight line segments of specified length.

### Editing contours

Once the contour has been closed, you can edit it by moving the vertices of the polygon. Drag a selection box over the vertices you want to edit, and then drag the selected vertices to move them.

### Adding contours to the segmentation layer

A contour is not added to the segmentation layer until you press the accept button. When you accept the contour, its interior is filled with the currently selected drawing label.