This filter is accessible through Filters/Artistic/Mosaic and gives you the power to apply a range of mosaic effects. The mosaic tiles are surrounded by a black border and the colors of the tiles themselves are based on the colors of the original image. Any spaces between tiles are colored black.
Once you have entered the "Mosaic" dialog you have various options.
In the Tiling Primitives box, choose the basic mosaic shape:
Squares
Polygons
Polygons & Squares
In the Parameters box, set the following as you wish:
Tile Size: the size of the tiles between 5 and 100. The higher the value the fewer the tiles used to comprise the image.
Tile Height: the height of the tiles between 1 and 50.
Tile Spacing: the spacing of the tiles between 1 and 50. The lower the value the tighter the fit between the tiles.
Tile Neatness: the degree of neatness, or regularity of shape, of the tiles between 0 and 100%. The lower the value the more irregular the tile shapes.
Light Direction: the angle the light falls on the tiles between 0 and 360 degrees.
Color Variation: the color differences between the tiles can be heightened or lowered between 0 and 100%. The lower the value the closer the tiles are in color.
In the Options box tick the boxes to set the following:
Anti-aliasing: This is a technique for softening the edges of the individual mosaic tiles by surrounding their edges with a one-pixel transition.
Color Averaging: This alter the colors of the individual tiles so that they are an average of their own color and the surrounding colors.
Pitted Surfaces: The tiles are given a pitted look, rather like an image of the surface of the moon.
FG/BG Lighting: The edges of the tiles are traced in the current foreground and background colors, according to the colors of the tiles they surround.
All your settings are shown in the Preview box.
See: