The marching ants effect is an animation technique often found in

selection Selection may refer to: Science * Selection (biology), also called natural selection, selection in evolution ** Sex selection, in genetics ** Mate selection, in mating ** Sexual selection in humans, in human sexuality ** Human mating strat ...

tools of

computer graphics Computer graphics deals with generating images with the aid of computers. Today, computer graphics is a core technology in digital photography, film, video games, cell phone and computer displays, and many specialized applications. A great deal ...

programs. It helps the user to distinguish the selection border from the image background by animating the border. The border is a dotted or dashed line where the dashes seem to move slowly sideways and up and down. This creates an illusion of ''ants marching in line'' as the black and white parts of the line start to move. Some prefer the term marquee selection, as the effect resembles the

chaser lights A chase is an electrical application where strings of adjacent light bulbs cycle on and off frequently to give the illusion of lights moving along the string. With computerized lighting consoles, building chase sequences has become easier, whil ...

of a marquee, and this term can be considered a synonym. Popular graphics programs, such as the

GIMP GIMP ( ; GNU Image Manipulation Program) is a free and open-source raster graphics editor used for image manipulation (retouching) and image editing, free-form drawing, transcoding between different image file formats, and more specialized ...

and Adobe Photoshop, implement their selection tools using the ''marching ants'' effect. The technique was first widely used by the MacPaint program developed by

Bill Atkinson Bill Atkinson (born March 17, 1951) is an American computer engineer and photographer. Atkinson worked at Apple Computer from 1978 to 1990. Atkinson was the principal designer and developer of the graphical user interface (GUI) of the Apple ...

. The easiest way to achieve this animation is by drawing the selection using a pen pattern that contains diagonal lines. If the selection outline is only one pixel thick, the slices out of the pattern will then look like a dashed line, and the animation can easily be achieved by simply shifting the pattern one pixel sideways and redrawing the outline. The method has the disadvantage of not looking like marching ants with selection borders that are not parallel to the coordinate axes.

Origin

With the selection problem in mind, Bill Atkinson went to his favorite pub in Los Gatos. Something on the wall caught his attention. It was an electric Hamm's Beer sign. The beer sign consisted of an illuminated scene of a kind of animated waterfall. Water seemed to flow down the waterfall into the lake. Bill figured that this effect could solve his problem because it is easily recognizable. He implemented the idea and showed it to Rod Perkins from the Lisa team, who told Bill the effect reminded him of "marching ants".MacPaint Evolution
at folklore.org

References

External links

Fun with marching ants
describes another scheme for generating the marching ants pattern {{DEFAULTSORT:Marching Ants Graphical user interface elements History of computing