Using the Region Tools

You can use the Region tools to select a portion of 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 pane, as shown below. Other parameters, such as the minimum, maximum and mean values of a dataset within the region, are available in region histograms (see Plotting Region Histograms).

Region properties and settings

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

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

Region 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.

Perimeter

Indicates the perimeter of the contour line that defines the region.

Area

Indicates the precise area inside the contour line that defines the region. You should note that Dragonfly calculates sub-pixels* for area measurements.

Click to the Histogram button open the Region Histogram dialog, in which you can profile the intensity distribution within a selected area. Additional parameters, such as the minimum, maximum and mean values of a dataset within the region, are available in region histograms (see Plotting Region Histograms).

* 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.

You can use any of the Region tools, as described in the following table, to select a portion of an image.

Region tools

 

 Icon Description

Rectangle

You can use the Rectangle tool to select a rectangular portion of an image.

  • Click on the image and then drag to shape and size the rectangular region. Release the mouse to create the region.

Ellipse

You can use the Ellipse tool to select an elliptical portion of an image.

  • Click on the image and then drag to shape and size the elliptical region. Release the mouse to create the region.

Polygon

You can use the Polygon tool to select a polygonal portion of an image.

  • Click on a succession of points to define the contour of the region.
  • Click a control point to end the region.

Freehand

You can use the Freehand tool to select a freehand portion of an image.

  • Click and then drag to define the required contour. Release the mouse to create the region.
  1. Maximize the required image, recommended.
  2. Click the required region tool in the Annotate panel.
  3. Select the required portion of the image, as described in the above table.

    The area of the region is indicated onscreen, while the perimeter and area are indicated in the lower section of the Data Properties and Settings panel.

A number of editing options are available for regions. You can move regions, reshape rectangular and elliptical regions, as well as adjust the position of the control points that define the polygonal and freehand regions.

  1. Select the required region, either directly in the 2D view or in the top section of the Data Properties and Settings panel.
  2. Select any section of the region between its control points and then drag to reposition the annotation.
  1. Select the required region, either directly in the 2D view or in the top section of the Data Properties and Settings panel.
  2. Click and drag a control point to reshape the region.

    The region measurements are updated automatically.

You can adjust a polygonal or freehand region by repositioning one or more of its control points.

  1. Select the required region, 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 region measurements are updated automatically.

  3. Click inside the selected control point(s) to de-select it.
  1. Select the required polygonal or freehand region, either directly in the 2D view or in the top section of the Data Properties and Settings panel.
  2. Do the following, as required:
    • Double-click the region between control points to add a control point.
    • Double-click a control point to remove it from the region.

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

Default configured actions for regions

Action

Key

Mouse

Create an elliptical region in Ellipse mode

-

Left mouse

Edit an elliptical region in Ellipse mode

-

Left mouse

Create a freehand region in Freehand mode

-

Left mouse

Edit a freehand region in Freehand mode

-

Left mouse

Create an polygonal region in Polygon mode

-

Left mouse

Edit an polygonal region in Polygon mode

-

Left mouse

Create a rectangular region in Rectangle mode

-

Left mouse

Edit a rectangular region in Rectangle mode

-

Left mouse

Add or remove control points from paths and regions

Left Shift

Double-click

Switch to Ellipse mode

-

-

Switch to Freehand mode

-

-

Switch to Polygonal mode

-

-

Switch to Rectangle mode

-

-
See Configurable Actions for information about modifying the default actions for the Region tools.