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By component I meant any class that extends the Component class.
By visible I meant a component whose isDisplayable() method returns true.

Try adding some printlns in different places to see if...

Try calling createImage() in a component that is visible.

Move the code to another class?
What are the values of the args to the createImage() method?

Have you read the API doc for the createImage() method to see what it returns?

Is the dbImage variable null? Why doesn't it have a valid non null value?
Can you post your current code?