photomosaic

Photomosaic, also called image mosaic, is a digital artwork produced by assembling a large number of smaller images into a single composite. When viewed from a distance, the larger image is discernible due to the collective color and tonal properties of the tiles; up close, the individual photographs may be identified. The technique relies on a library of source images and a mapping process that assigns tiles to regions of the target image.

Construction typically proceeds by sampling the target image at regular intervals to form a grid. For each grid cell, a candidate tile whose average color or other feature best matches the cell is selected from the library. The chosen tile is color-adjusted and scaled to fit the cell, and tiles are then arranged in a mosaic. Optional blending, edge-smoothing, and brightness/contrast corrections can improve visual cohesion.

Variants include different tile shapes, adaptive tiling to preserve detail in darker areas, or content-aware selection to reduce redundancy. Efficient algorithms use approximate nearest-neighbor search, color histograms, k-means clustering, or feature vectors to speed up tile matching, especially when libraries contain thousands of images.

Applications span art installations, advertising, album covers, and education. Photomosaics are also used in data visualization and creative coding projects to explore relationships among many images.