"good artist copy, great artist ateal" - Pablo Picaso

This is common practise in art. The image needs to only be changed a little but to be able to claim ownership of it ( something small like caning the colours is usual enough to legally claim it as your own for copyright as an art pace).

Remember Warhol's Marilyn Monro screen print? that's a photograph from the paper but screen printed repetitively using different colours...so ya know a literal copy but with various colours is one of the biggest art pieces of the 20th century. Its a supper common (and encouraged) practise in art to reappropriate other peoples shiz.

and really, there is not much difference in visual result or creative integrity to look at a photograph...or the building itself in real life and then draw it on the paper as accurately as possible without tracing ( even its like a more skillful tracing of the mind) but its still valid practise even though nothing new or original is being drawn - thats why there are so many boring samey paintings of the efiel tower, from the same view, maybe in different colours, but they are all originals and okay for the 'artist' to sell