The child's practised eye instantly noted his father's state. He dived under the table, where experience had taught him was a rather safe place. The dog, lacking skill in such matters, was, of course, unaware of the true condition of affairs. He looked with interested eyes at his friend's sudden dive. He interpreted it to mean: Joyous gambol. He started to patter across the floor to join him. He was the picture of a little dark-brown dog en route to a friend.
It's from 'A dark brown dog' by Stephen Crane in 1893.
What does the picture mean exactly?
It sounds a bit odd for me to just interpret it 'image or figure' in the flow of sentence.