The first thing to do is to get evidence of the infringement. If your work has been used without permission, get a copy of the publication. If the infringement is on the web, print out the pages that display your image along with enough information to positively identify the site and date. The next thing to do is to identify the infringer. You are then in a position to contact them and take the matter further. How you do all this and what outcome you may be able to achieve will likely depend on the extent and context of their infringement. Many factors may apply. Are they passing your work off as their own, or is it credited to you? Is the metadata intact or has it been altered? Is their usage personal or commercial? Whereabouts are they located? Broadly your choices are:

• You can insist that they remove the image immediately.
• You can offer to supply a retrospective licence on payment of a fee, to legiitimise the infringing use. Plus a further fee for agreed future use, if appropriate.
• You can commence legal proceedings against them for infringement of your copyright.
• You can forget it and give up