You can look in the IJ_Props.txt file the exact plugin called by a given menu command.

For example for the 'Make Binary' menu entry, the IJ_Props.txt file reads

binary01="Make Binary",ij.plugin.Thresholder

You'll find a copy of the IJ_Props.txt file in your ij.jar file or at http://rsb.info.nih.gov/ij/download/IJ_Props.txt

Then visit the source code page at http://rsb.info.nih.gov/ij/developer/source/index.html

and go to the correct class, in our example the ij.plugin.Thresholder class.

Another option to discover which class is called by a given menu item, is to enable the debug mode by checking the 'debug mode' checkbox under Edit/Options/Misc… dialog, run the investigated function from the menus and read the log output.

For our example, the debug log reads :

actionPerformed: time=1228576256194, java.awt.event.ActionEvent[ACTION_PERFORMED,
cmd=Make Binary,when=1228576256194,modifiers=] on menuitem1
runPlugin: ij.plugin.Thresholder 

With “Fiji” ImageJ version, the IJ_Props.txt file don't contain all menu descriptions.

For example, the menu “Analyze / Directionality” isn't in “IJ_Props.txt” file and the “Debug mode” solution log :

actionPerformed: time=12512156, java.awt.event.ActionEvent[ACTION_PERFORMED,
cmd=Directionality,when=1339586662984,modifiers=] on menuitem0
runPlugin: fiji.analyze.directionality.Directionality_  

This plugin is stored in the following file : “Fiji.app\plugins\Directionality_.jar”

You can see the link between the plugin and the menu in the text file “Fiji.app\plugins\Directionality_.jar\plugins.config” :

# Directionality, builder Jean-Yves Tinevez   
Analyze, "Directionality", fiji.analyze.directionality.Directionality_