This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. Please help to improve this article by introducing more precise citations. (May 2012)

The compose key and compose LED on Sun Type 5, 6 and 7 keyboards is the second-last key on the bottom row.

The compose key on a DEC LK201 keyboard is the leftmost key on the bottom row.

A compose key, available on some computer keyboards, is a special kind of modifier key designated to signal the software to interpret the following sequence of two (or more) keystrokes as a combination in order to produce a character not found directly on the keyboard. For example, striking Compose followed by A and then E may produce the ligature æ, whereas striking Compose followed by O and then C can yield © (circled C, the copyright symbol).

The compose key can be found on the LK201 family of keyboards from Digital Equipment Corporation and its successors. The key can also be found on keyboards from Sun Microsystems. However, any key on a keyboard can be configured to serve as a compose key, as long as the functionality is supported by the software in use.

Usage[link]

The compose key is different from a typical modifier key (such as AltGr or ⌥ Option) in that, rather than being pressed and held while another key is struck, it is pressed and released before striking the keys to be modified. Typically, the text-entry system does not indicate that any keys have been pressed until the composed character appears after the final keystroke of a predefined sequence. Therefore, the compose key can also be described as a kind of generic dead key. What makes the compose key different from a dead key is that while each dead key can only be used to attach a specific diacritic to various base letters, the compose key can be used to produce any kind of a character supported by the character set and font in use. This way, an even wider variety of special characters can be made available on a keyboard with a limited number of keys.

In a loose sense, the character produced with a compose-key sequence can be seen as a precomposed character, but it does not need to be technically decomposable or have any visual resemblance with the characters normally produced with the same keys (i.e., without striking the compose key first). Nevertheless, there is usually some kind of an association that helps to make the key sequence more mnemonic. For example, typing Compose followed by T and then H may produce the Icelandic (as well as Old Norse and Old English) letter þ (thorn), which phonetically corresponds to the digraph th in, e.g., thing.

Compose key in various computer systems[link]

The compose key is known as "Multi_key" in the X Window System, and must be interpreted by the client program (typically Xlib), not the server. In XFree86 and X.Org Server, many keyboard layouts have a variant that maps Multi_key to some key, usually (on PC keyboards) to either of the Windows keys, or ⇧ Shift+AltGr ^[1] or sometimes ⇧ Shift+Right-Ctrl.^{[citation needed]} It can also be specified in XkbOptions (for example, "compose:rwin"), it can be manually enabled with the command "setxkbmap -option compose:rwin", whereas on Debian-like distributions it can be enabled through Debconf ("dpkg-reconfigure keyboard-configuration").

Multi_key can also be assigned with the xmodmap(1) utility. Note that it is common for ⇧ Shift+AltGr to be mapped to the compose key, but for AltGr+⇧ Shift to be mapped to the fourth "keyboard level" modifier.^{[clarification needed][2]} (The first three levels correspond to holding no modifiers, ⇧ Shift, and AltGr respectively.) So for example the copyright symbol, © can be typed using the compose key as ⇧ Shift+AltGr, o, c, or using the level four modifier as AltGr+⇧ Shift+c.

ISO/IEC 9995-7 assigned to this key a graphical symbol ⎄, which exists in Unicode as U+2384 since version 3.0.0 of the standard.^[3] However, this symbol doesn't appear to be used by the industry.

Originally the currency sign on the keyboards were nationalized, and not every keyboard sold in the world contained a dollar sign ($), which explains why it appears there^{[clarification needed]}, although it is part of any standard^{[by whom?]} keyboard since the 1990s. In particular the $ compose sequence ceased to work^[when?] on modern^[which?] systems. The historic backslash sequence (compose-//) witnesses of the similar situation for this key and is still working on modern systems.

Microsoft Windows does not use a compose key as such, but a few programs such as PuTTY provide compose key support. There are also a number of open source utilities (such as AllChars) and installable keyboard layouts available that emulate the compose key using a selectable modifier key like Control or AltGr.

Common compose combinations[link]

The table shown below contains the current common compositions for Xorg 7. Other compositions may work, based on the de-facto Sun/DEC/Falco standard. Particularly for modern systems which support customizable compose sequences and Unicode, the table would be far from complete.^[4]

See also[link]

• Modifier key
• Dead key
• AltGr key
• Windows Alt keycodes
• Precomposed character
• Combining character

References[link]

External links[link]

• Linux Compose Key Sequences with equivalent unicode mappings
• XFree86 Compose Key character map by XFree86
• Everything2's list of Compose Key combinations
• SUN's Compose Key combinations used under CDE
• Setting up Compose Key in the X Window System
• AllChars, an open-source utility that emulates the Compose key under MS-Windows
• FreeCompose, an open-source Compose key utility for Windows.
• JLG Extended Keyboard Layout - yet another utility based on the Compose Key mechanism under Windows
• Installable keyboard layouts for Windows with source for editing in the MSKLC keyboard editor
• Accent Composer - Compose accented characters and other symbols under Microsoft Windows. Unicode compatible
• Compose key sequences used in GNOME/GTK

This article may require copy editing for grammar and tense. You can assist by editing it. (August 2011)

Today's practicality of green screen compositing is demonstrated by Iman Crosson in a self-produced YouTube video.
Top panel: A frame of Crosson in a full motion video that was shot in his own living room.
Bottom panel: The corresponding frame in the final version, in which Crosson, impersonating Barack Obama, "appears" in the White House's East Room.^[1]

Chroma key compositing, or chroma keying, is a special effects / post-production technique for compositing (layering) two images or video streams together, 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 top layer is made transparent, revealing another image behind. 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^[2]), 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 and no part of the subject being filmed or photographed may duplicate a color used in the background.^[3] It is commonly used for weather forecast broadcasts, wherein the news presenter appears to be standing in front of a large map during live television newscasts, though in actuality it is a large blue or green background. When using a blue screen, different weather maps are added on the parts of the image where the color is blue. If the news presenter wears blue clothes, his clothes will also be replaced with the background video. A complementary system is used for green screens. Chroma keying is also used in the entertainment industry for special effects in movies and videogames. The advanced state of the technology and much commercially available computer software, such as Pinnacle Studio, Adobe Premiere, and dozens of other computer programs, makes it possible and relatively easy for the average home computer user to create videos using the "chromakey" function and easily affordable greenscreen or bluescreen kits.

History[link]

In filmmaking, a complex and time-consuming process known as "travelling matte" was used prior to the introduction of digital compositing. The blue screen and traveling matte method were developed in the 1930s at RKO Radio Pictures and other studios, and were used to create special effects for The Thief of Bagdad (1940). At RKO, Linwood Dunn used a travelling matte to create "wipes" – where there were transitions like a windshield wiper in films such as Flying Down to Rio (1933).

The development of the bluescreen is credited to Larry Butler, who won the Academy Award for special effects for The Thief of Bagdad.

In 1950, Warner Brothers employee and ex-Kodak researcher Arthur Widmer began working on an ultra violet travelling matte process. He also began developing bluescreen techniques: one of the first films to use them was the 1958 adaptation of the Ernest Hemingway novella, The Old Man and the Sea, starring Spencer Tracy.^[4]

The background footage is shot first and the actor or model is filmed carrying out their actions against a bluescreen. To simply place the foreground shot over the background shot would create a ghostly image over a blue-tinged background. The actor or model must be separated from the background and placed into a specially-made "hole" in the background footage. The bluescreen shot was first rephotographed through a blue filter so that only the background is exposed. A special film is used that creates a black and white negative image — a black background with a subject-shaped hole in the middle. This is called a 'female matte'. The bluescreen shot was then rephotographed again, this time through a red and green filter so that only the foreground image was cast on film, creating a black silhouette on an unexposed (clear) background. This is called a 'male matte'.

The background image is then rephotographed through the male matte, and the shot rephotographed through the female matte. An optical printer with two projectors, a film camera and a 'beam splitter' combines the images together one frame at a time. This part of the process must be very carefully controlled to ensure the absence of 'black lines'. During the 1980s, minicomputers were used to control the optical printer. For The Empire Strikes Back, Richard Edlund created a 'quad optical printer' that accelerated the process considerably and saved money. He received a special Academy Award for his innovation.

One drawback to the traditional traveling matte is that the cameras shooting the images to be composited can't be easily synchronized. For decades, such matte shots had to be done "locked-down" so that neither the matted subject nor the background could shift their camera perspective at all. Later, computer-timed motion control cameras alleviated this problem, as both the foreground and background could be filmed with the same camera moves.

Petro Vlahos was awarded an Academy Award for his development of these techniques. His technique exploits the fact that most objects in real-world scenes have a color whose blue color component is similar in intensity to their green color component. Zbigniew Rybczyński also contributed to bluescreen technology.

For Star Trek: The Next Generation, an ultraviolet light matting process was proposed by Don Lee of CIS and developed by Gary Hutzel and the staff of Image G. This involved a fluorescent orange backdrop which made it easier to generate a holdout matte, thus allowing the effects team to produce effects in a quarter of the time needed for other methods.^[5]

Some films make heavy use of chroma key to add backgrounds that are constructed entirely using computer-generated imagery (CGI). Performances from different takes can even be composited together, which allows actors to be filmed separately and then placed together in the same scene. Chroma key allows performers to appear to be in any location without even leaving the studio.

Computer development also made it easier to incorporate motion into composited shots, even when using handheld cameras. Reference-points can now be placed onto the colored background (usually as a painted grid, X's marked with tape, or equally spaced tennis balls attached to the wall). In post-production, a computer can use the references to adjust the position of the background, making it match the movement of the foreground perfectly. Modern advances in software and computational power have even eliminated the need to use grids or tracking marks – the software analyzes the relative motion of colored pixels against other colored pixels and solves the 'motion' to create a camera motion algorithm which can be used in compositing software to match the motion of composited elements to a moving background plate.

Weathermen often use a field monitor to the side of the screen to see where they are putting their hands. A newer technique is to project a faint image onto the screen.

Process[link]

Film set for The Spiderwick Chronicles, where a special effects scene using bluescreen chroma key is in preparation.

The principal subject is filmed or photographed against a background consisting of a single color or a relatively narrow range of colors, usually blue or green because these colors are considered to be the furthest away from skin tone.^[3] The portions of the video which match the preselected color are replaced by the alternate background video. This process is commonly known as "keying", "keying out" or simply a "key".

Green is currently used as a backdrop more than any other color because image sensors in digital video cameras are most sensitive to green, due to the bayer pattern allocating more pixels to the green channel, mimicking the human eye's increased sensitivity to green light.^[6] Therefore, the green camera channel contains the least "noise" and can produce the cleanest key/matte/mask. Additionally, less light is needed to illuminate green, again because of the higher sensitivity to green in image sensors.^[7] Bright green has also become favored as a blue background may match a subject's eye color or common items of clothing, such as jeans, or a dark-navy suit.

Blue was used before digital keying became commonplace because it was necessary for the optical process, but it needed more illumination than green. However, it is also further in the visual spectrum from red, the predominant color in human skin.

The most important factor for a key is the color separation of the foreground (the subject) and background (the screen) – a bluescreen will be used if the subject is predominately green (for example plants), despite the camera being more sensitive to green light.

In analog color TV, color is represented by the phase of the chroma subcarrier relative to a reference oscillator. Chroma key is achieved by comparing the phase of the video to the phase corresponding to the preselected color. In-phase portions of the video are replaced by the alternate background video.

In digital color TV, color is represented by three numbers (red, green, blue). Chroma key is achieved by a simple numerical comparison between the video and the preselected color. If the color at a particular point on the screen matches (either exactly, or in a range), then the video at that point is replaced by the alternate background video.

Clothing[link]

A chroma key subject must not wear clothing similar in color to the chroma key color(s) (unless intentional), because the clothing may be replaced with the background video. An example of intentional use of this is when an actor wears a blue covering over a part of his body to make it invisible in the final shot. This technique can be used to achieve an effect similar to that used in the Harry Potter films to create the effect of an invisibility cloak. The actor can also be filmed against a chroma key background and inserted into the background shot with a distortion effect in order to create a cloak that is marginally detectable.^[8]

Difficulties emerge with bluescreen when a costume in an effects shot must be blue, such as Superman's traditional blue outfit. In the 2002 film Spider-Man, in scenes where both Spider-Man and the Green Goblin are in the air, Spider-Man had to be shot in front of the greenscreen and the Green Goblin had to be shot in front of a bluescreen, because Spider-Man wears a costume which is red and blue in color and the goblin wears a costume which is entirely green in color. If both were shot in front of the same screen, one character would have been partially erased from the shot.

Background[link]

Demonstration of the creation of special effects techniques utilizing chroma key.

Blue is generally used for both weather maps and special effects because it is complementary to human skin tone. The use of blue is also tied to the fact that the blue emulsion layer of film has the finest crystals and thus good detail and minimal grain (in comparison to the red and green layers of the emulsion.) In the digital world, however, green has become the favored color because digital cameras retain more detail in the green channel and it requires less light than blue. Green not only has a higher luminance value than blue but also in early digital formats the green channel was sampled twice as often as the blue, making it easier to work with. The choice of color is up to the effects artists and the needs of the specific shot. In the past decade, the use of green has become dominant in film special effects. Also, the green background is favored over blue for outdoors filming where the blue sky might appear in the frame and could accidentally be replaced in the process. Although green and blue are the most common, any color can be used. Red is usually avoided due to its prevalence in normal human skin pigments, but can be often used for objects and scenes which do not involve people.

Occasionally, a magenta background is used, as in some software applications where the magenta or fuchsia key value #FF00FF is sometimes referred to as "magic pink".^[9]

With better imaging and hardware, many companies are avoiding the confusion often experienced by weather presenters, who must otherwise watch themselves on a monitor to see the image shown behind them, by lightly projecting a copy of the background image onto the blue/green screen. This allows the presenter to accurately point and look at the map without referring to monitors.

A newer technique is to use a retroreflective curtain in the background, along with a ring of bright LEDs around the camera lens. This requires no light to shine on the background other than the LEDs, which use an extremely small amount of power and space unlike big stage lights, and require no rigging. This advance was made possible by the invention of practical blue LEDs in the 1990s, which also allow for emerald green LEDs.

There is also a form of color keying that uses light spectrum invisible to human eye. Called Thermo-Key, it uses infrared as the key color, which would not be replaced by background image during postprocessing.^[10][11]

Even lighting[link]

The biggest challenge when setting up a bluescreen or greenscreen is even lighting and the avoidance of shadow, because it is best to have as narrow a color range as possible being replaced. A shadow would present itself as a darker color to the camera and might not register for replacement. This can sometimes be seen in low-budget or live broadcasts where the errors cannot be manually repaired. The material being used affects the quality and ease of having it evenly lit. Materials which are shiny will be far less successful than those that are not. A shiny surface will have areas that reflect the lights making them appear pale, while other areas may be darkened. A matte surface will diffuse the reflected light and have a more even color range. In order to get the cleanest key from shooting greenscreen it is necessary to create a value difference between the subject and the greenscreen. In order to differentiate the subject and screen a two-stop difference can be used, either by making the greenscreen two stops higher than the subject or vice versa.

Sometimes a shadow can be used to create a special effect. Areas of the bluescreen or greenscreen with a shadow on them can be replaced with a darker version of the desired background video image, making it look like the person casting the shadow is actually casting a shadow on the background image instead.

Another common, related, problem is lighting the subjects in a manner that is complementary to the scene being keyed in behind. Attention has to be paid to matching the direction of lighting and the color balance in the background. Any spill of the chroma key color will make the result look unnatural. Even a difference in the focal length of the lenses used can affect the success of chroma key.

Exposure[link]

Another challenge for bluescreen or greenscreen is proper camera exposure. Underexposing or overexposing a colored backdrop can lead to poor saturation levels. In the case of video and digital cinema cameras, underexposed images can contain high amounts of noise, as well. The background must be bright enough to allow the camera to create a bright and saturated image.

Programming[link]

There are several different quality- and speed-optimized techniques for implementing color keying in software.^[12]

In most versions, a function f(r, g, b) → α is applied to every pixel in the image. α (alpha) has a meaning similar to that in alpha compositing techniques. α ≤ 0 means the pixel is the green screen, α ≥ 1 means the pixel is in the foreground object. Values between 0 and 1 indicate a pixel that is partially covered by the foreground object. A usable green screen example, which matches how chroma key was done on an optical printer, is f(r, g, b) = K₀ * b − K₁ * g + K₂ (K_0..2 are user-adjustable constants, 1 is a good initial guess for all of them).

Often the software does screen spill removal from the colors as well as figure out the alpha. This may be a separate function g(r, g, b) → (r, g, b), a very simple green screen example is g(r, g, b) → (r, min(g, b), b). Or f is changed to return (r, g, b, a) all at once, this is useful if part of the calculation is shared.

Most keyers use far more complicated functions. A popular approach is to describe a closed 3D surface in RGB space and determine the signed distance the point (r, g, b) is from this surface, or to find the distance the point (r, g, b) is between two closed nested surfaces. It is also very common for f() to depend on more than just the current pixel's color, it may also use the (x, y) position, the values of nearby pixels, the value from reference images, and values from user-drawn masks.

A different class of algorithm tries to figure out a 2D path that separates the foreground from the background. This path can be the output, or the image can be drawn by filling the path with α = 1 as a final step. An example of such an algorithm is the use of active contour. Most research in recent years has been into these algorithms.

See also[link]

• Compositing
• Federal Standard 1037C
• Filmmaking
• Drew Carey's Green Screen Show
• Film production
• Front projection effect
• Live action
• Matte (filmmaking)
• Muslin
• Optical printer
• Primatte chromakey technology
• Rear projection effect
• Reverse bluescreen
• Schüfftan process
• Signal processing
• Sodium vapor process
• Special effects
• Video switcher
• Virtual set

References[link]

External links[link]

• Building a Chroma Key on a low budget (Google Knol)
• How Blue Screens Work
• Stargate Studios Virtual Backlot Reel 2012 -- An awesome demonstration of green screen work!!!

Song In (in hangul 송인, in hanja 宋仁) was a civil official in the mid-Goryeo era who became the intermediary founder of the Jincheon Song clan. His highest post was munha pyeongjangsa (문하 평장사). This was the highest government position in the period. Song In was responsible for administration, judicial affairs and economy in the district.^[1]

As he performed meritorious deeds during the King, he was conferred with Chanhwagongsin and Jincheonbaek. Baek was a position of politicians who were responsible for administration, judicial affairs and economy in the district. As the government created him Jincheonbaek, his family started regarding Jincheon as their origin. Hence, the family origin became Jincheon Song.

When he was in the position of Sangsanbaek, he tried to be just and fair in all the administrative affairs and strived to enhance the welfare of his people. He also focused on education for the youth and courtesy for people, which made his district famous for most excellent behaviors in the nation. After that, the people have long paid tribute to his feats.

During the insurrection of Yi Jagyeom in the 4th year of King Injong of Goryeo's reign in 1126, he was killed by a rebellious band led by Cheok Jun-gyeong while escorting the king. After the rebels were put down, Song In was posthumously named 'meritous subject' and titled Lord Sangsanbaek (상산백).

Song In was born in Durujinmaeul (village), Duchon-ri, Deoksan-myeon in 1125 during the reign of King Injong of the Goryeo Dynasty. He was promoted to Pyeonjangsa, which was the highest government position in the period.

Tomb of Song In[link]

Chungcheongbuk-do Monument No. 91 Location: Duchon-ri, Deoksan-myeon, Jincheon-gun

This is the tomb of Song In (?-1126). It has a rectangular-shaped protective wall surrounding the tomb, typical of the Goryeo style. There are two tombstones erected in the late Joseon Dynasty period.

In the grave area, there are many tombs that belong to the clan. In front of his tomb stands the jaesil (chamber for memorial rites) with the tablet reading 'Sangsanjae'.

His grave is in Duchon-ri, Deoksan-myeon, which had been called Duruji, Sanjeong-myeon. The beautiful peak behind his grave is called Mountain Bibong which was named after Bongsae (bird) that is said to live in heaven and to fly down to sit on the summit. However, after the statue was inscribed of In Gong, the founder of Jincheon Song, the peak was compared to a slowly dropped ume flower. Thus, Mountain Bibong was called Maesanbibong, in which 'Mae' was named after an ume flower instead of a bird.

As he was a meritorious subject and served as a Pyeongjangsa (higher government official), the government ordered his grave mound to be surrounded by stones and a monument. The grave is one of the oldest ones in Jincheon and is recorded in Seokchong (stone tomb) in Hwanyeoseungram.

Thousands of descendents of Jincheon Song are living across the nation. Song Guk-cheom and Song Eon-gi who were devoted to fight against the Mongolian invasion into Goryeo are also the offspring of Jincheonbaek.

See also[link]

• Song (Korean name)
• Bon-gwan

References[link]

External links[link]

• Photo of the tomb
• Song In
• Monument 91, Tomb of Song In
• Jincheon Song bon-gwan information (Korean)
• Jincheon Song bon-gwan website (Korean)
• http://www.jincheon.go.kr/english/sub04/sub0404_01.jsp

This Korean biographical article is a stub. You can help Wikipedia by expanding it. v t e

This Korean history-related article is a stub. You can help Wikipedia by expanding it. v t e