In Greek mythology and later Roman mythology, the Cyclopes (/saɪˈkloʊpiːz/ sy-KLOH-peez; Greek: Κύκλωπες, Kýklōpes, "Circle-eyes" or "Round-eyes"; singular Cyclops /ˈsaɪklɒps/ SY-klops; Κύκλωψ, Kýklōps) are giant one-eyed creatures. Three groups of Cyclopes can be distinguished. In Hesiod's Theogony, the Cyclopes are the three brothers Brontes, Steropes, and Arges, who made for Zeus his weapon the thunderbolt. In Homer's Odyssey, they are an uncivilized group of shepherds, the brethren of Polyphemus encountered by Odysseus. Cyclopes were also famous as the builders of the Cyclopean walls of Mycenae and Tiryns. In Cyclops, the fifth-century BC play by Euripides, a chorus of satyrs offers comic relief based on the encounter of Odysseus and Polyphemus. The third-century BC poet Callimachus makes the Hesiodic Cyclopes the assistants of smith-god Hephaestus; as does Virgil in the Latin epic Aeneid, where he seems to equate the Hesiodic and Homeric Cyclopes. From at least the fifth century BC, Cyclopes have been associated with the island of Sicily and the volcanic Aeolian Islands.
Chroma key compositing, or chroma keying, is a special effects / post-production technique for compositing (layering) two images or video streams together based on color hues (chroma range). The technique has been used heavily in many fields to remove a background from the subject of a photo or video – particularly the newscasting, motion picture and videogame industries. A color range in the foreground footage is made transparent, allowing separately filmed background footage or a static image to be inserted into the scene. The chroma keying technique is commonly used in video production and post-production. This technique is also referred to as color keying, colour-separation overlay (CSO; primarily by the BBC), or by various terms for specific color-related variants such as green screen, and blue screen – chroma keying can be done with backgrounds of any color that are uniform and distinct, but green and blue backgrounds are more commonly used because they differ most distinctly in hue from most human skin colors. No part of the subject being filmed or photographed may duplicate the color used as the backing.