computer science

Pixelation

Pixelation is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Pixelation rather than just read about it. In short: In computer graphics, pixelation (also spelled pixellation in British English) is caused by displaying a bitmap or a section of a bitmap at such a large size that individual pixels, small single-colored square display elements that comprise the bitmap, are visible. Such an image is said to be pixelated (pixellated in the UK).

Key takeaways

Pixelation belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Pixelation to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Pixelation from memory before moving on to harder problems.

Reference excerpt

In computer graphics, pixelation (also spelled pixellation in British English) is caused by displaying a bitmap or a section of a bitmap at such a large size that individual pixels, small single-colored square display elements that comprise the bitmap, are visible. Such an image is said to be pixelated (pixellated in the UK).

Early graphical applications such as video games ran at very low resolutions with a small number of colors, resulting in easily visible pixels. The resulting sharp edges gave curved objects and diagonal lines an unnatural appearance. However, when the number of available colors increased to 256, it was possible to gainfully employ anti-aliasing to smooth the appearance of low-resolution objects, not eliminating pixelation but making it less jarring to the eye. Higher resolutions would soon make this type of pixelation all but invisible on the screen, but pixelation is still visible if a low-resolution image is printed on paper. In the realm of real-time 3D computer graphics, pixelation can be a problem. Here, bitmaps are applied to polygons as textures. As a camera approaches a textured polygon, simplistic nearest neighbor texture filtering would simply zoom in on the bitmap, creating drastic pixelation. The most common solution is a technique called pixel interpolation that smoothly blends or interpolates the color of one pixel into the color of the next adjacent pixel at high levels of zoom. This creates a more organic, but also much blurrier image. Pixelation is a problem unique to bitmaps. Alternatives such as vector graphics or purely geometric polygon models can scale to any level of detail. This is one reason vector graphics are popular for printing – most modern computer monitors have a resolution of about 100 dots per inch, and at 300 dots per inch printed documents have about nine times as many pixels per unit of area as a screen. Another solution sometimes used is procedural textures, textures such as fractals that can be generated on-the-fly at arbitrary levels of detail.

Deliberate pixelation In some cases, the resolution of an image or a portion of an image is lowered to introduce pixelation deliberately. This effect is commonly used on television news shows to obscure a person's face in order to protect their privacy or to censor nudity or vulgar gestures, and is also used for artistic effect. This effect is called pixelization. Making pixels easily visible is also a main feature in pixel art which is where the graphics are made in low resolutions for effect.

Depixelization Depixelization removes pixelization from images, attempting to reconstruct the appearance of the original (unpixelated) image.

See also Colour banding Macroblocking Posterization Pixel art

References

Further reading Bachmann, Talis (2016). Perception of Pixelated Images. doi:10.1016/C2015-0-04793-1. ISBN 978-0-12-809311-5.

External links Zooming Without Pixelation, digital camera advice by Mark Coffman Pixelization of a Font by Stephen Wolfram, The Wolfram Demonstrations Project.

Illustrations

Pixelation: An example of pixelation. The image looks smooth when zoomed out, but when a small section is viewed more closely, the eye can distinguish individual pixels. — An example of pixelation. The image looks smooth when zoomed out, but when a small section is viewed more closely, the eye can distinguish individual pixels.

Pixelation: A diamond without (left) and with (right) anti-aliasing — A diamond without (left) and with (right) anti-aliasing

Pixelation: The zoomed portion of the cat image above, resized using nearest neighbor (left) and with Adobe Photoshop's bicubic resampling, which uses pixel interpolation (right). The interpolated image has no sharp edges, but is considerably blurrier. — The zoomed portion of the cat image above, resized using nearest neighbor (left) and with Adobe Photoshop's bicubic resampling, which uses pixel interpolation (right). The interpolated image has no sharp edges, but is considerably blurrier.

Worked examples

Example 1 — a first encounter with Pixelation

Start with the simplest possible case. Write down what Pixelation claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Pixelation before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Pixelation ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Pixelation

In research: Pixelation appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Pixelation in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Pixelation is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer graphic artifacts, so understanding it makes those chapters shorter.
In everyday life: Look for Pixelation outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Pixelation in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Pixelation means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Pixelation out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Pixelation in simple terms?

Why does Pixelation matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Pixelation?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Pixelation.