a picture of
the picture of (something)
The ideal example of something (which is listed after "of"). Yes, Jill was in the hospital a few months ago, but she's the picture of health now. We went running together just the other day.
(very) picture of something
Fig. the perfect example of something; an exact image of something. The young newlyweds were the picture of happiness. My doctor told me that I was the very picture of good health.
a (or the) picture of —the embodiment of a specified state or emotion.
1989 Woman's Realm The…little girl looks a picture of health in her blue dungarees and red boots.