Use the Automatic Threshold dialog box to have the thresholds in an gray-value image set automatically.
Setting threshold values is necessary to define objects in an image for an object analysis. Phases will be defined in the image by appropriate threshold values. You can find more information on threshold values and phases here.
Opening the dialog box
You open this dialog box, via the Count and Measure tool window. Load a gray-value image. Select the Automatic Threshold... entry, in the Threshold button's context menu. You open this menu by clicking the small arrow next to the button. Should this entry already have been selected, click the Automatic Threshold... button directly.
The dialog box's structure
The dialog box is made up of several groups. Click on one of the areas in the dialog box shown above to jump to the corresponding help topic.
(1) Setting background options
(2) Defining phases
(4) Channel display
(6) Loading, saving, and managing threshold values
See also
Carrying out an automatic image analysis
Tool Window - Count and Measure
(1) Setting background options
In the Background group, you define whether the bright or the dark image structures, or alternatively the complete image, are to be used for the automatic analysis. The term background is used in this context for all of the image structures that are not within the threshold values.
Select the Dark option if the dark image structures are to be used as background. In this case, bright image structures will be defined as a phase and will be evaluated in the automatic analysis.
Select the Bright option if the bright image structures are to be used as background.
Select the Automatic option if the classifying of the image structures as either phase or background, is to occur automatically. In this case your software evaluates the images histogram. Please note that the number of phases to be defined isn't automatically adjusted. The number of phases to be defined has to be set correctly so that the image structures can be correctly allocated to a phase.
Select the None option if no image area is to be defined as background. In this case, the complete image will be evaluated when the automatic analysis is carried out.
In image (1), you can see objects with three different gray intensity values.
In image (2), the bright image structures are the background. The rest of the image is allocated to one single phase. The phase is colored red here.
In image (3), the dark phases are defined as background. The bright phase is detected.
In image (4) no background has been chosen, all image structures are defined as phases. In this case, three phases are defined.
(2) Defining phases
Use the Phase thresholds for channel '...' group to define phases.
Adding phases
Click on the Add Phase 
button to create a phase.
Double click the field in the Class Name column to enter a name for the corresponding phase.
Double click the field in the Color column to open the color palette and to select a color for the corresponding phase. The phase will be displayed in the color you have assigned it, in the image window and in the histogram.
The threshold value for the phase will be automatically calculated. In the [Min. field, the threshold value range's lower value will be specified. In the Max.[ field, the higher value will be specified. The higher value itself no longer belongs to the threshold value range. The values will be calculated from the displayed histogram.
Deleting phases
Click the Remove Phase 
button to delete a phase. At least one phase will always be defined. It's only possible to remove a phase when two phases have been defined.
(3) Histogram display
The histogram shows the current image's intensity distribution. You can find more information on the histogram display here.
(4) Channel display
In the Channel group, the active image's channels are shown.
As a rule, your images only contain one channel. The standard name for this channel is Gray.
(5) Setting preview options
Use the Preview of phases group to display the phases in color in the image when setting the thresholds. By using the Preview you will have a direct visual control over which image areas belong to a phase and which don't. The phases are only displayed in color as long as the dialog box for setting thresholds is open.
Select the None option to have the preview switched off. None of the phases that have been defined will be displayed in the image in color.
Select the Current option to have only the currently selected phase shown in its assigned color in the image. All other phases that have been defined are now hidden.
Select the All option to have all of the defined phases shown in the image, in their assigned colors.
Select the Transparent option to make it possible to recognize the image structures despite the phases being displayed in color.
Even when the dialog box for setting threshold values is open, you can still use your software's zoom functions as usual. Move your mouse pointer onto the appropriate position in the image, then use the mouse wheel to zoom into or out of the image.
The default setting for the Preview of phases group, is the All option. Every time you reopen the dialog box, the All option will therefore be initially set.
(6) Loading, saving, and managing threshold values
Use these buttons to load, save or change the threshold value settings. You can save the following settings to a parameter set: The phase's name, the number of phases and the colors assigned to them.
When automatically setting threshold values, the intensity ranges belonging to the individual phases are recalculated for each image.
You will find more information on working with parameter sets here.
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