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You might even be able to pass the JLabel into the JOptionPane.showMessageDialog() method as the second parameter instead of outputArea. I'm not sure though, as I haven't played with it at all.

So you want the image to display instead of the outputArea JTextArea?

Just add the icon to a JLabel, then put the JLabel in a JDialog. Show the JDialog instead of calling...

That is waaay too much code for us to wade through. Make it easy for people to help you by providing an SSCCE that demonstrates only the problem you're having, without any extra stuff. Narrow it...