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A mosaic refers to a plurality of non-overlapping images, arranged in some tesselation. A photomosaic is a picture made up of various other pictures (pioneered by Robert Silvers), in which each "pixel" is actually another picture, when examined closely.
A tile mosaic is a digital picture made up of individual tiles, arranged in a non-overlapping fashion, e.g. to make a static image on a shower room or bathing pool floor, by breaking the image down into square pixels formed from ceramic tiles (a typical size is 1 inch by 1 inch, as for example, on the floor of the University of Toronto pool, though sometimes larger tiles such as 2 by 2 inch are used). These digital images are coarse in resolution, and often simply express text, such as the depth of the pool in various places, but some such digital images are used to show a sunset, or other beach theme. Obviously digital images expressed in ceramic tile are of very low resolution.
Digital cameras typically give images in a mosaic fashion, the most common mosaic being the Bayer pattern, as shown below:
R G
G B
where there are two green pixels, and one red and one blue in each 4 by 4 submosaic.
A common goal of image processing is what is called demosaicing, i.e. a reversal of the mosaicing that takes place in nearly all digital cameras.
Thus apart from the artistic value (i.e. the work of Robert Silvers, and others who use mosaicing creatively), the mosaicing is usually considered an artifact to be filtered out, through interpolation.
Many modern digital cameras provide the mosaic file, e.g. Nikon provides the "NEF" file, and the end user can demosaic it, rather than using the camera's firmware to do the demosaicing.
Another common spelling of "demosaicing" is "demosacking".
Mosaicing refers to the process of undoing the in-camera interpolation, e.g. recovering the Nikon NEF file from a JPEG image, and is usually done by "reverse engineering" the camera.
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