A photographic mosaic or photomosaic is a picture (usually a photograph) that has been divided into tiled sections, usually equal sized, each of which is replaced with another photograph that matches the target photo.[1] When viewed at low magnifications, the individual pixels appear as the primary image, while close examination reveals that the image is in fact made up of many hundreds or thousands of smaller images.[1] Most of the time they are a computer-created type of montage.
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.
- ^ a b Cartwright (2007) p.102 quote: Photographic mosaic, also known as Photomosaic, a portmanteau of photo and mosaic, is a picture that is divided into small sections. When viewed as a whole, it appears to be one image, when in fact the image is made up of hundreds or even thousands of smaller images.