Photographic mosaic

There are two kinds of mosaic, depending on how the matching is done. In the simpler kind, each part of the target image is averaged down to a single color. Each of the library images is also reduced to a single color. Each part of the target image is then replaced with one from the library where these colors are as similar as possible. In effect, the target image is reduced in resolution (by downsampling), and then each of the resulting pixels is replaced with an image whose average color matches that pixel.

In the more advanced kind of photographic mosaic, the target image is not downsampled, and the matching is done by comparing each pixel in the rectangle to the corresponding pixel from each library image. The rectangle in the target is then replaced with the library image that minimizes the total difference. This requires much more computation than the simple kind, but the results can be much better since the pixel-by-pixel matching can preserve the resolution of the target image.

History

• 1973 Leon Harmon publishes The Recognition of Faces. It is illustrated with a very pixelated version of the portrait of Abraham Lincoln in the 5-dollar bill.
• 1974-1976 Salvador Dalí paints two versions of Gala Contemplating the Mediterranean Sea which at a distance of 20 meters is transformed into the portrait of Abraham Lincoln (Homage to Rothko). The gray blocks in Harmon's portrait are substituted by square-shaped subpictures forming the image of a nude Gala Dalí looking through a window.
• 1977 Dalí prints a lithograph Lincoln in Dalivision based in his previous paintings.
• 1993 Joseph Francis, working for R/Greenberg Associates in Manhattan, is believed to be the inventor of the modern-day computer-generated colour image versions. His Live from Bell Labs poster created in 1993 used computer-themed tile photographs to create a mosaic of a face (Ryszard Horowitz/ Photography and Art Direction, Robert Bowen/ Digital Artist). He went on to create a mosaic for Animation Magazine in 1993, which was repeated in Wired Magazine (November 1994, p. 106). Francis has said on his "History of Photo Mosaics" webpage that his interest in developing these techniques further was in part stimulated by the work of artist Chuck Close.
• 1994 Dave McKean creates an image for DC Comics, a mosaic of a face made from photos of faces, although this is believed to be created manually using Photoshop.

• 1994 Adam Finkelstein and Sandy Farrier create a mosaic of John F. Kennedy from parts of Marilyn Monroe pictures. The result was displayed in the Xerox PARC Algorithmic Art Show in 1994.
• 1994 Benetton: AIDS - Faces mosaic. Over one thousand young peoples' portraits from all over the word computer-processed spell out the word AIDS.

• 1995 The Gioconda Sapiens, a face with ten thousand faces, was presented to the public in April 1995 (Spain, Domus museum). This was the first large photographic mosaic, using photographs of 10,062 people from 110 countries to make the Mona Lisa.
• 1995 Adam Finkelstein (published mosaic in Mossy Bits) creates a mosaic of the 1930 oil painting by Grant Wood, American Gothic, from images collected from the Web in early 1995.
• 1995 Robert Silvers creates an algorithm for generating Photomosaics programmatically and goes on to trademark the term Photomosaic and patent his process for creation of Photomosaics in 1997. The name Photomosaic and an implementation concept were trademarked by Robert Silvers' Runaway Technology, Inc.
• 2000 Andrej Olejnik creates the first pattern-based photographic mosaics rendered with Mosaic Creator software.