Creating Whitebox GAT plugin tools

By John Lindsay, Ph.D. (Last modified, May 2013)

Please note that this tutorial only applies to Whitebox GAT v. 2.0 and higher. The 1.0 series of Whitebox GAT was developed using the .NET framework and not Java.

Creating a Whitebox GAT plugin tool can be quite a fast and painless process once you have the steps down. Whitebox tools are generally written in Java, although you can use any programming language targeting the Java Virtual Machine (JVM), including Scala, Groovy, Jython, and Kotlin. Generally development is made easier if you use an integrated development environment (IDE), such as Netbeans. An IDE is simply an environment for computer programming and there are many very good, free IDEs that are used for Java development. Whitebox has been developed using the Netbeans IDE, which you may want to download and install for this tutorial.

1. Using the Netbeans IDE, create a new Java project. There are a few things that you need to configure before coding the new tool.

2. First, add a new package called 'plugins' to the 'Source Packages' (right-click over 'Source Packages' and select 'Java Package').

3. Now add a new Java class to 'plugins' it whatever you will, but this name will be important for other things so you should put some thought into it. It should be relatively short, contain no spaces or numbers, and should be descriptive of what the tool does (unlike the 'MyTool' tool in the example above!). Notice as well that the Java convention for class names is camel-case, i.e. capitalize the first letter and any concatenated words.

4. Add a new folder called 'META-INF/services' to the source packages. Notice that although you will use the path separator, it will appear as a dot in 'Source Packages'. Letter case is important here.

5. Within 'META-INF/services', add a new FILE called 'whitebox.interfaces.WhiteboxPlugin'. Open this file and enter a line for your new plugin tool, e.g. plugins.MyTool for the MyTool plugin tool. You can have as many plugin tools within the plugins package as you like but each of them need to have a 'plugin.' line entry in this file in order to be visible as a plugin to the main Whitebox GUI.

6. You will likely need to add the WhiteboxAPI.jar to your Library folder. This file will allow you to read/write Whitebox files and Shapefiles and a number of other important functions.

7. Now open '' or whatever file is associated with your newly created tool.

8. Launch Whitebox GAT, open the dialog for whatever tool is closest to the tool that you are creating and press the 'View Code' button on the dialog box. Copy and paste the code from this tool into the java file for your new tool. Be sure to erase anything that may be in the new file before pasting.

9. There will be a number of quick modifications to the code that you will need to make now. First, if your new tools does not reside within the same package (jar file) as the tool you just pasted the code from, you will need to alter the package statement on the first line; in the example from the image above, the MyTool class would need to have a first line that states, 'package JohnLindsaysTools' in reference to the JohnLindsaysTools.jar file that will be created when I compile my project. You will also need to change the class name at the top so that it matches the name of your new tool (i.e. the name of the java file). Also change the return string within the 'getName' function to this very same name. You also need to change the returns of the 'getDescriptiveName' (this is the name that your tool is given in the tools list and tree and can contain spaces, unlike the getName version of the tool name) and the 'getToolDescription' (this is the bit of text that will appear along the status bar when the user clicks on your tool in the tools list or tree).

10. Unless your tool will occupy the same toolbox as the tool from which you copied the code, you will need to update the 'getToolbox' return string array. Your tool can be listed in multiple toolboxes within the tools tree, with each one occupying a cell in this string array. You can find out the names of the various existing toolboxes, or create a new toolbox, by examining/editing the toolbox.xml file contained within the 'Resources' folder of Whitebox (itself contained within the 'lib' folder). Alternatively you can simply examine the 'getToolbox' returns of a tool contained within the toolbox that you want your new tool to occupy.

11. The real work done by your tool is contained within the 'run' method of the code. You can learn how to work with Whitebox files simply by examining the code of several existing tools. You will likely notice several similarities in the structures of these tools. For example, the various parameters that will be fed to the program are usually ingested early in the method by assigning the various elements of the 'args' array to variables. Input and output raster images are then generally initialized before performing any sort of analysis. Nearer the end of the 'run' method you will likely find that input/output files are closed and returns are fed back to Whitebox using the 'returnData' function. This function accepts an Object. If the return is a string value containing the full file name, including directory, of a WhiteboxRaster or Shapefile, the Whitebox GUI will automatically display the file in the map area. If it contains a string of data, it will be displayed within the text area of the Whitebox GUI. If it contains a jPanel, the panel will be embedded in a jDialog and displayed by the GUI (e.g. see the 'FeatureSpacePlot' tool as an example of this). This is also useful if you want to create a custom dialog for a more complicated plugin tool.

12. If you examine the source code of several Whitebox tools, you may notice that some of them contain a commented-out main function near the bottom of the code file. This function is used for debugging purposes only. Although most Whitebox plugin tools are not meant to be executed independently from the main GUI (i.e. they are part of plugin libraries), by creating a main function you are able to hard-code input parameters and launch the tool. This provides a convenient means for debugging. Just be sure to comment out or delete this method before including the tool in Whitebox.

13. Once you are done debugging your new tool, compile the project, find the newly created jar file contained within the projects 'dist' folder and copy it into the 'plugins' folder within Whitebox's 'Resources' folder. Whitebox will now discover your new tool when it launches. If Whitebox is already open, close it and re-launch it. Your new tool should be listed in the specified toolbox(es) within the tools tree and also in the tools list.

14. The next thing that you have to do is to write the instructions for Whitebox to create a dialog when the user selects your new tool. Most tools in Whitebox use a standard set of input parameters, which are then fed to the plugin tools when the user selects the 'OK' button on the tool dialog. (Note: not all tool need to use a standard dialog and it is possible for you to embed a custom dialog in Whitebox as well by returning a jPanel.) The instructions to draw a tool dialog are contained in an xml file, which is located in the 'Dialogs' folder within the 'plugins' folder, and which has the same name as your tool (i.e. the short name, or class name, and not the descriptive name). It's probably easiest if you find a tool with similar input and output parameters to your own and simply copy and modify its dialog xml file as needed. Importantly, the order of the parameters in this file must match the order in which you ingest the parameters of the 'args' array within the tool's run method.

15. That's it. Now all you need to do is to create an accompanying help file for your new tool. If you haven't already created one, then when you open the tool's dialog you will notice a button on the lower right-hand side that says 'Create New Help Entry'. If you press this button, you will be presented with another dialog that will allow you to create the html file that will become the tool's associated help file. It will automatically contain the formatting necessary for a Whitebox help entry and will be saved in the appropriate folder for it to be discovered the next time that the dialog is opened.'ve just created a new Whitebox GAT tool!