Truth is an absolute defense to defamation (slander is spoken defamation; libel is written defamation). Also, opinions, name calling, insults and slurs are protected speech. So I do not see a successful defamation action for the comments made. However, it could be an invasion of privacy--depending on who took the picture, for what purpose and where it was taken. More info is needed. Also, you would need proof that it was your ex.
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