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Tips and Tricks

ImageJ is easy to use, but sometimes you wish for some function that is actually implemented, yet you do not know how to trigger. This page lists a few of those tricks.

Show the memory consumption

Just click on the status bar, and you will see how much memory is used, and how much memory is available.

Execute external programs

The macro language allows executing programs, and capturing their output:

output = exec("dir /w");

Quickly see return values

You do not need to wrap macro calls into write() calls: if you just write something like


the return value will appear in your Log window when called.

Find out in which menu (or .jar file) a certain command is

Hit ⌃ Ctrl + L to use the search bar. Type (part of) the name of the entry, then click on Show full information.

If EditOptionsMisc…>Require command key for shortcuts is unchecked, typing L is sufficient.

Put the main window to the foreground

Pressing the ↵ Enter key on any image will bring the main window to the foreground.

Close all images (without being asked whether to save them)

PluginsUtilitiesClose All Without Saving

Set the foreground color

Double-click on the pipette, or press ⌃ Ctrl / ⌘ ⌃ Ctrl on a PC ⌘ command on a Mac  + ⇧ Shift + K, or select the menu item ImageColorColor Picker….

Set the line width

Line selections can have a width larger than one, which also has an effect on line profiles. You can set it by double clicking on the line selection tool, or by calling EditOptionsLine Width…

Quickly copy a ROI from one image to another

Simply activate the image with the desired ROI, then the image you want to put that ROI into, and press ⌃ Ctrl + ⇧ Shift + E. This triggers the EditSelectionRestore Selection which “restores” the selection.