Pixelization

Pixelization is a video- and image-editing technique in which an image is blurred by displaying part or all of it at a markedly lower resolution. It is primarily used for censorship. The effect is a standard graphics filter, available in all but the most basic bitmap graphics editors.

Pixelization as censorship
A familiar example of pixelization can be found in television news and documentary productions, in which vehicle license plates and faces of suspects at crime scenes are routinely obscured to maintain the presumption of innocence, as in the television series COPS. Bystanders and others who do not sign release forms are also customarily pixelated. Footage of nudity (including genitalia, buttocks, or breasts) is likewise obscured in some media: before the watershed in many countries, in newspapers or general magazines, or in places in which the public cannot avoid seeing the image (such as on billboards). Drug references may also be censored in this manner. Pixelization is not usually used for this purpose in films, DVDs, subscription television services, pornography (except for countries in which the law requires it). When obscene language is censored by an audible bleep, the mouth of the speaker may be pixelated to prevent lip reading.

Pixelization may also be used to avoid unintentional product placement, or to hide elements that would date a broadcast, such as date and time stamps on home video submissions. Censorship for such purposes is most common on reality television series.

Pixelization in art
Pixelization has also been used for artistic effect, notably in the art print The Wave of the Future, a reinterpretation of Katsushika Hokusai's The Great Wave at Kanagawa. In this updated print, the image of the large ocean wave shifts from the traditional style of the Japanese woodcut print to a pixelated image and finally to a wireframe model computer graphics image.

Pixelization in online forums
Pixelization is used to post pornographic or illegal images on public messageboards and imageboards. This form of pixelization is created using specific algorithms which can be undone to reveal the original image. This practice is used on boards such as 4chan and 2chan, and is often called "GMasking", after an application commonly used to perform the task.

Alternative techniques
For many censorship purposes, pixelization has been supplanted by blurring the image, or black rectangular or square boxes (known as censor bars) may be used to cover parts of images completely (for example, a black box inserted over the eyes rather than pixelization of the entire face).

A drawback of pixelization is that any differences between the large pixels can be exploited in moving images to reconstruct the original, unpixelated image; squinting at a pixelated, moving image can sometimes achieve a similar result. In both cases, integration of the large pixels over time allows smaller, more accurate pixels to be constructed in a still image result. Completely obscuring the censored area with pixels of a constant color or pixels of random colors escapes this drawback but can be more aesthetically jarring.

International legal standards
Nudity is obscured on network television in the U.S. Japanese pornography laws require that genitals in films (including animated works) be obscured. In Thailand, restrictions are placed on television broadcast depiction of cigarettes being smoked, alcohol being consumed, or guns being pointed at people. Pixelization is the most common method of censoring this content.