Question: Jeffrey Mendler, a professional photographer, signed a licensing agreement with Winterland Production, Ltd., a manufacturer of screen-printed apparel, that allowed Winterland to use several photographs that Mendler had taken of the America's Cup yacht race as "guides, models, and examples, for illustrations to be used on screenprinted T-shirts or other sportswear." Several years later, Mendler discovered that Winterland had put out a line of T-shirts that displayed a digitally altered version of the image from one of Mendler's photographs. Winterland had scanned Mendler's photograph and had flipped the image horizontally, had reconstructed the missing tip of a sail that had been cut off in the original photograph, and had altered the colors of the sky somewhat. Mendler complained that the licensing agreement did not authorize such a use and that Winterland had infringed upon his copyright. Winterland argued that the changes that it had made had altered the image on the T-shirt from a photograph to an illustration based on a photograph. The parties agree that the license did not authorize Winterland to use photographic reproductions of Mendler's work but only to use the photographs as a "guide, model, or example" to achieve an end result that was an "illustration" and not a photographic reproduction. What must a plaintiff show to establish copyright infringement? Has infringement occurred here?