Pixelization
Pixelization (British English, pixelisation) or mosaic is any technique used in editing images or video, whereby an image is blurred by displaying part or all of it at a markedly lower Image resolution. It is primarily used for censorship. The effect is a standard graphics filter, available in all but the most basic bitmap graphics editors.
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, such as how it appears in the television series COPS. Bystanders and others who do not sign release forms are also customarily pixelized. Footage of nudity (including male and female genitals, buttocks, nipples, pubic hair, or areolae) 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, as well as gestures considered obscene (such as the finger) may also be censored in this manner. Pixelization is not usually used for this purpose in films, DVDs, subscription television services, or 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 pixelized to prevent lip reading, such as in COPS. Graphic injuries and excess blood may also be pixelized.
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.
Alternative techniques
A black rectangular or square box (known as censor bars) may be simply be used to occlude parts of images completely (for example, a black bar covering the eyes instead of the entire face being pixelized). Censor bars were extensively used as a graphic device in the January 2012 protests against SOPA and PIPA.
A drawback of pixelization is that any differences between the large pixels can be exploited in moving images to reconstruct the original, unpixelized image; squinting at a pixelized, 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.
An additional drawback, when pixelization is used to reduce the repulsing, disturbing or, more generally shocking, aspect of an image, is that all information contained in the pixelized area are lost for the audience. Other visual processing techniques, on the other hand can help reduce the shocking aspect of images or videos while preserving most of the information of the media.
Samples where pixelation might be used
- A familiar example of pixelization can be found in television news and documentary productions, where 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 the genitalia, buttocks, or breasts) is likewise obscured in some media: before the watershed in many countries, in newspapers or general magazines, or in places where the public cannot avoid seeing the image (such as on billboards).
- Drug references may also be censored in this manner. However in cinemas, on DVD and subscription television services, in pornography (except for the countries where the law requires it), and in men's magazines, pixelization is not usually used for this purpose.
- When obscene language is censored by an audible bleep, the mouth of the speaker may be pixellated to prevent lip reading.
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