pixelization

{{Short description|Blurring technique in images or videos}}

{{About|the graphical editing/censorship technique|the undesirable phenomenon in which individual pixels are visible|Pixelation|the stop motion animation technique|Pixilation}}

{{Refimprove|date=December 2008|article on image censorship}}

Pixelization (in British English pixelisation) or mosaic processing 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 resolution. It is primarily used for censorship. The effect is a standard graphics filter, available in all but the most basic bitmap graphics editors.

In media

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 off Kanagawa. In this updated print, the image of the large ocean wave shifts from the traditional style of the Japanese woodcut print to a pixelized image and finally to a wireframe model computer graphics image.vorpal.us: [http://vorpal.us/2007/07/wave-of-the-future-is-now-the-past/ "Wave of the Future is now the Past"]. Retrieved July 13, 2009vorpal.us: [http://vorpal.us/img/waveofthefuture.jpg "High resolution image of 'Wave of the Future'"]. Retrieved July 14, 2009 Westworld (1973) was the first feature film to use digital image processing to pixelize photography to simulate an android's point of view.

The 2010 third-person cover shooter Kane & Lynch 2: Dog Days also used pixelization for artistic purposes, as nudity and headshots are pixelated in the game, to make the game appear more like user-generated content.

Alternative techniques

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A black rectangular or square box (known as censor bars) may 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;{{cite journal |last1=Newton |first1=EM |last2=Sweeney |first2=L |last3=Malin |first3=B |title=Preserving privacy by de-identifying face images |journal=IEEE Transactions on Knowledge and Data Engineering |date=Jan 2005 |volume=17 |issue=2 |pages=232–243 |doi=10.1109/TKDE.2005.32 |s2cid=1813467 |url=https://dataprivacylab.org/dataprivacy/projects/video/paper.pdf}} 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 is lost for the audience.{{cite journal|last1=Besançon|first1=Lonni|last2=Semmo|first2=Amir|last3=Biau|first3=David|last4=Frachet|first4=Bruno|last5=Pineau|first5=Virginie|last6=Sariali|first6=El Hadi|last7=Soubeyrand|first7=Marc|last8=Taouachi|first8=Rabah|last9=Isenberg|first9=Tobias|last10=Dragicevic|first10=Pierre|title=Reducing Affective Responses to Surgical Images and Videos Through Stylization|journal=Computer Graphics Forum|volume=39|issue=1|year=2019|pages=462–483|issn=0167-7055|doi=10.1111/cgf.13886|doi-access=free}} Other visual processing techniques can help reduce the shocking aspect of images or videos while preserving most of the information of the media.{{cite book|last1=Besançon|first1=Lonni|last2=Semmo|first2=Amir|last3=Biau|first3=David|last4=Frachet|first4=Bruno|last5=Pineau|first5=Virginie|last6=Sariali|first6=El Hadi|last7=Taouachi|first7=Rabah|last8=Isenberg|first8=Tobias|last9=Dragicevic|first9=Pierre|title=Proceedings of the Joint Symposium on Computational Aesthetics and Sketch-Based Interfaces and Modeling and Non-Photorealistic Animation and Rendering|chapter=Reducing affective responses to surgical images through color manipulation and stylization|year=2018|pages=1–13|doi=10.1145/3229147.3229158|isbn=9781450358927|s2cid=51928057|url=https://hal.inria.fr/hal-01795744/file/Besancon_2018_RAR.pdf}}

See also

References

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