Appropriation vs. Plagiarism

In my opinion there is a very fine line between plagiarism and appropriation. Plagiarism is the direct theft of another artists art and claiming it as your own, for an example creating a master copy of Vincent Van Gogh's Starry Night and signing your own name. Artistic appropriation is stealing another artists work and slightly altering it (50% or less) to create a new "image" or something another. Famous artists such as Andy Warhol, Pablo Picasso, and many other highly respected artists use artistic appropriation in very successful pieces.