An FDNY firefighter slugged a stranger whose wife cut in front of him as he posed for a photo in front of Medgar Evers College in Brooklyn late Friday, cops said.

Kenneth Boyke, 43, began arguing with the man — and then socked him in the face — after his wife spoiled the photo in front of the school on Bedford Avenue near Crown Street in Crown Heights around 9:25 p.m., police said.

It wasn’t clear whether the firefighter — or the couple — had been attending an event at the school.

Boyke was arrested and charged with assault and harassment. The victim, 41, was treated at the scene.