Indigo Buntings?

Seeing these birds at Heckscher State Park was the perfect ending to the day. When I first saw them they were on the ground close to the road that loops around the park.  They resembled house finches that had been dipped in blue dye. I think they are Indigo Buntings, but they might be Blue Grosbeaks. I'm no ornithologist. If you can tell from my photo what is, please let me know.