Parent Topic: CLWORKS

Aggregate

The ``Aggregate'' panel is launched from the Classify menu on the main ImageWorks window. The Aggregate function allows the user to interactively aggregate up to 255 classes together. Using the clustering results, the user can display classes in different colours (using a pseudo-colour table), group classes into aggregates, and assign different names and colours to each aggregate.

There are four main areas of the panel:

The top most area contains the current file, input, and output channel. These may be changed by selecting the ``Setup ...'' button at the bottom of the panel

To aggregate classes, you must first select classes from the Input Classes list. You may select just one input class or (using the CTRL or SHIFT keys) select multiple classes for aggregation.

You must then select a class to represent this aggregate in the Aggregate Classes list on the right. You can select only one class.

After both the aggregate class and the input classes have been selected, pressing the ``Add'' button in the middle will establish the aggregate.

The Remove button may be used to disassociate one or more input classes from their respective aggregate.

Once all the classes have been aggregated, press ``Apply to Output Channel'' to write the results to disk.

The ``Load Area'' panel presents an interface by which you can choose which area you wish to work in.

Setup

When the ``Aggregate'' function is first selected you are presented with the Aggregate setup panel from which you can chose the input and output of the aggregation. The input channel is typically the result of an unsupervised classification. The output channel is an empty channel which is used to store the results of the aggregation.

This panel may also be accessed through the ``Setup ...'' button on the aggregate panel itself. You can use this to change the input or output channels of the aggregate function.

Viewing Options

This section provides a set of radio buttons for choosing different ways of viewing classes and aggregates.

This section also contains a colour swatch and a means of editing it. This colour swatch is used to indicate which colour the system should use when displaying the highlighted classes in the Input Classes list. The ``Highlight Classes'' button must also be depressed in order for this to work.

Input Classes

This is a multiple selection table that allows the user to select one or more classes. You can select multiple classes by holding down the Shift or CTRL key while making your selection.

Once the class or classes are selected, they may be assigned to an aggregate class by highlighting or creating a class in the ``Aggregate List'' and then pressing the ``Add >>'' button.

In addition, by clicking in the main image window with the right mouse button, the selected class will be highlighted.

Pressing the ``Select Class at Cursor'' button will select the class at the current cursor location.

The ``Highlight Classes'' button is used to draw the selected classes in the Highlight Colour displayed in the Viewing Options section.

Finally the PCT allows the user to recolour all of the classes in the input list based either on a PCT, or by generating a PCT such that it looks similar to the channels and enhancements specified.

Aggregate Classes

This is a table representing the list of aggregate classes. You may use the buttons below the table to create, delete, or import classes.

You may also multiselect classes for deletion by selecting a class and pressing the Shift or CTRL key simultaneously.

Load
This panel is used to initialize a class list that is to import definitions of classes from either a text file or from the meta-data associated with a channel.

You may choose to import class names, values, and colour from almost any file and channel. The classes are not actually imported until you press the ``Accept'' button. The classes you see in the panel are merely a preview of what the classes would like if you imported them.

The ``Overwrite existing classes'' option allows the user to ignore existing class definitions in the class list and replace them from the import list.


Class List Format
This section describes the format of a text file containing class information. The format used is quite simple. The file is limited to one class per line and has four fields delimited by a ``|'' character.

The first field is the value. The second field contains the name. The third field contains the colour which is represented as an RGB tuple in the following format: 

  (RGB: rrr ggg bbb)
The fourth field is the description of the class.

The last field is a list of associated class values, this is used only to save aggregation session information. This field is optional

Here is an example of a text field describing three classes: 

1 | Water        | (RGB: 0 0 255) | Water class | 10,20
2 | Crop         | (RGB: 0 255 0) | Crops       |
3 | Other Class  | (RGB: 255 0 0) | Water class | 40
Save
This panel allows the user to save the existing session so that it may be loaded at a later time. The text file contains all the information related to the Aggregate classes, including the source classes which comprise the aggregate. This text file may then be used to initialize subsequent sessions using the "Load" facitlity.

If the text file specified already exists, it may be overwritten.

To load a session select the "Load" button and a "Class Initialization" panel will appear. Select the "Text File" tab, then choose the file using the "Text File ..." button. Press Accept to confirm the load.

See Also: Class List Format

Add or Remove Aggregates

The ``Add'' button is used to add one or more classes from the ''Input Class List'' to the ``Aggregate List''.

The ``Add'' button is made available only when an aggregate is selected from the ``Aggregate List'' and one or more "Unassigned" classes are selected from the ``Input Class List''.

The ``Remove'' button is used to remove classes from one or more aggregates. Only classes that have been assigned to an aggregate can be removed from aggregates. The ``Remove'' button is activated when classes are selected that have been assigned to aggregates.

Apply To Output Channel

The ``Apply to Output Channel'' action button along the bottom of the panel will perform the aggregate mapping to the output image channel.

The mapped aggregates will have grey level values that were specified as the aggregate value. The classes that have not been aggregated will be copied directly to the output channel.

The class names, colours, and description will also be written out as an output channel.

For example: Given the following class/aggregate relation: 

     Original Class List               Aggregate List

     0:Set to Lake(255)                40:Wheat(10,30)
    10:Set to Wheat(40)               255:Lake(0)
    20:Not Assigned
    30:Set to Wheat(40)
    40:Not Assigned
After the "Apply to Output Channel" has been pressed, the output image will contain 3 different classes: 

       Gray Levels             Descriptions
       of Output Image

           20                  Same at the original class list.
           40                  Contains Original classes 40, 10, and 30.
          255                  Contains only class 0.
Parent Topic: CLWORKS
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