Using the Path Tool

You can use the Path tool to draw curves on an image. Measurements are shown with the annotation in 2D and 3D views and are also available in the lower section of the Data Properties and Settings panel, as shown below. Additional options available for the Path tool include profiling the intensity values along its length (see Profiling Intensity).

Path properties and settings

See Annotation Properties and Settings for information about changing the visibility of paths and their assigned color, as well as other options available for annotations.

The measurements and tools available for paths are described in the following table.

Path measurements and tools

 

Description

Thickness

Indicates the thickness, in screen percentage, of the annotation.

  • Enter a new value in the Thickness edit box to change the thickness of the annotation.

Path

Indicates the length of the path

Area

For closed paths, indicates the precise area inside the contour line that defines the region. You should note that Dragonfly calculates sub-pixels* for area measurements.

Closed… Select this option to automatically close the selected path and calculate the area described by the contour line.

Smooth

Allows you to smooth curves by a selected magnitude.

  • Select a kernel size in the Kernel size drop-down menu and then click the Smooth button.

Resample

Allows you to reduce the number of control points that define the path.

  • Select the number of required control points in the Control points count drop-down menu and then click the Resample button.

Click the Profile tool to profile intensity values along the length of the path (see Profiling Intensity).

* Sub-pixel resolution, which can be used to measure within an accuracy that exceeds the nominal pixel resolution of an image, can be obtained in images that contain well-defined lines, points, or edges.

Whenever you create a path with the Path tool, control points are added along the path automatically as you drag to create the required curve. Dragonfly will automatically compute a Catmull-Rom spline to link the points that define the curve. You should note that Catmull-Rom splines are a family of cubic interpolating splines formulated such that the tangent at each point is calculated using the previous and next point on the spline.

  1. Maximize the required image, recommended.
  2. Click the Path tool in the Annotate panel.
  3. Click and then drag to create the path.

    The length of the path is indicated at its starting point and in the bottom section of the Data Properties and Settings panel.

A number of editing options are available for paths. You can adjust the position of the control points that define the path, add additional control points, and extend the length of a path. You can also smooth curves and resample paths. Refer to the table Path measurements and tools for more information about these options.

You can adjust a path by repositioning one or more of its control points.

  1. Select the required path, either directly in the 2D view or in the top section of the Data Properties and Settings panel.
  2. Click inside the control point or points you need to adjust and then drag.

    The path measurements are updated automatically.

  3. Click inside the selected control point(s) to de-select.
  1. Select the required path, either directly in the 2D view or in the top section of the Data Properties and Settings panel.
  2. Select any section of the path between its control points and then drag to reposition the annotation.

  1. Select the required path, either directly in the 2D view or in the top section of the Data Properties and Settings panel.
  2. Do the following, as required:
    • Hold down Left Shift and then double-click the path between control points to add a control point.
    • Hold down Left Shift and then double-click a control point to remove it from the path.
  1. Click the Path tool in the Annotate panel.
  2. Select the required path, either directly in the 2D view or in the top section of the Data Properties and Settings panel.
  3. Hold down Left Ctrl (or your configured key) and then click and drag one of the path end points.

    The path measurements are updated automatically.

  4. Click inside the selected control point to de-select it.

A number of configured actions and keyboard shortcuts are available for creating and editing paths. The default settings for these actions are listed in the following table.

Default configured actions for paths

Action

Key

Mouse

Create a path in Path mode

-

Left mouse

Edit a path in Path mode

-

Left mouse

Add or remove control points from paths and regions

Left Shift

Double-click

Extend a path with the Path tool

Left Ctrl

Left mouse

enterStatePathEditAddFromEdit

Left Ctrl

Left mouse

Switch to Path mode

-

-
See Configurable Actions for information about modifying the default actions for the Path tool.