GIGANTOSAURUS vs TRICERATOPS
Prehistory, also known as pre-literary history, is the period of human history between the use of the first stone tools by hominins c. 3.3 million years ago and the beginning of recorded history with the invention of writing systems. The use of symbols, marks, and images appears very early among humans, but the earliest known writing systems appeared c. 5000 years ago and it took thousands of years for writing systems to be widely adopted. In some human cultures, writing systems were not used until the nineteenth century and, in a few, are not even used until the present. The end of prehistory therefore came at very different dates in different places, and the term is less often used in discussing societies where prehistory ended relatively recently. Sumer in Mesopotamia, the Indus valley civilization, and ancient Egypt were the first civilizations to develop their own scripts and to keep historical records; this took place already during the early Bronze Age. Neighboring civilizations were the first to follow. Most other civilizations reached the end of prehistory during the Iron Age. The three-age system of division of prehistory into the Stone Age, followed by the Bronze Age and Iron Age, remains in use for much of Eurasia and North Africa, but is not generally used in those parts of the world where the working of hard metals arrived abruptly from contact with Eurasian cultures, such as Oceania, Australasia, much of Sub-Saharan Africa, and parts of the Americas. With some exceptions in pre-Columbian civilizations in the Americas, these areas did not develop complex writing systems before the arrival of Eurasians, so their prehistory reaches into relatively recent periods; for example, 1788 is usually taken as the end of the prehistory of Australia.
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.
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