Magic Wand

The magic wand tool provides an easy way to outline irregularly-shaped regions of interest or features in your image. Simply click on the Magic Wand tool, place the wand cursor inside the area that you want to trace, and click the left mouse button once. The magic wand will automatically trace the outline of the region/feature based on the color similarities and/or difference of intensity ranges between the pixel under your cursor and surrounding pixels, plus or minus a specified tolerance interval.

To outline more than one region, click on the tool in the Magic Wand group.  This enables the multi-select option.  Alternatively, you can simply hold the <Ctrl> key down while clicking on the regions you want to outline.

You can use the options in the Magic Wand pull-down menu to fine tune Image-Pro's edge detection mechanism.  Adjust these values if Image-Pro is having difficulty following an edge, or is tracing elements you do not want to include in your ROI.  See "Magic Wand Options" below for a detailed description of each option.

Once the Magic Wand selections are placed the way you want them over regions/features of interest in your image, you must validate the outlines for the purpose they are intended.  For example, if the outlines are intended as a generic annotation, you must validate them as annotations.  If you want the outlines to be used for measurement purposes, you must validate them as measurements.  If you want the outlines to be used as ROI markers, you must validate them as ROIs.    

To validate your Magic Wand selections:

  1. Click on the arrow in the Validate tool.

    The Validate menu is displayed.

  2. Select the option that will convert your magic wand selections as desired. 

Magic Wand Options

The various controls on the Magic Want dialog box are described below:

Interpretation: This control is only available for color images.  It determines the color model in which to interpret the seed point and the region pixels.  If you select RBG, Image-Pro interprets the pixels as having Red, Green, and Blue channels.  If you select HSI, Image-Pro interprets the pixels as having Hue, Saturation, and Intensity channels.  If you select HSL, Image-Pro interprets the pixels as having Hue, Saturation, and Lightness channels.  The latter two are often better for detecting edges based on differences in color.

Range: The Range value gives the intensity range over which the region pixels are allowed to vary around the seed point value (the value of the pixel you clicked on).  Image-Pro will look for edges where the intensity values of surrounding pixels are +/- ½ of the given range.  This value must be specified as an intensity value range according to the bit depth of the image you are working with.  The full intensity value range for Image-Pro supported bit depths are shown in the following table.  

BIt Depth

Full Range

8

0-255

12

0-4095

16

0-65535

24 RGB

0-255

36 RGB

0-4095

48 RGB

0-65535

32 Floating Point

0%-100%

For Mono images there is only one range value you can specify -- the Mono range.  For color images, there is a range value for each color channel in the image.  In color images, color channels can be interpreted in one of three ways: RGB, HSL (Hue/Saturation/Lightness), HSI (Hue/Saturation/Intensity).  Image-Pro interprets the image information according to one of these models depending on what is selected in the Interpretation list box.  

When you select an interpretation option, the labels for the Range controls are changed accordingly.  The Range value for each color channel specifies the range of values that pixels must have for that channel in order to be included in the seeded region.

Additionally, each Range option (each color channel) has a check box indicating whether that channel should be considered in the edge detection process.  For example, if you are using the RGB color model and you uncheck "Green," all green-channel pixel information will be ignored for the sake of determining the edges of the object of interest.  

Used in combination, these controls can be effective in finding edges based on different criteria.  For example, if you are interested in matching a particular color, you should pick HSL or HSI interpretation, and then turn on only the Hue and maybe Saturation channels for matching.

Smoothing: The Smoothing value varies from 0 (no smoothing) to 9 (high degree of smoothing).  This determines how much the boundary marker is smoothed after the region is detected.  

Filter:  Set this value to describe the level of contrast between the feature you are tracing and surrounding elements.  The threshold scale extends from 1 to 100.  A low value represents low contrast; a high value, high contrast.

Fill Holes: Holes are regions within the outer-most border of a feature of interest that are distinct from the feature. When the Fill Holes option is not selected, the Magic Wand tool draws outlines around the holes.

When the Fill Holes option is selected, the Magic Wand tool does not draw outlines around the holes.