Pixel is a unit of length and area

I&#x27;d say it&#x27;s better to call it a unit of counting.<p>If I have a bin of apples, and I say it&#x27;s 5 apples wide, and 4 apples tall, then you&#x27;d say I have 20 apples, not 20 apples squared.<p>It&#x27;s common to specify a length by a count of items passed along that length. Eg, a city block is a ~square on the ground bounded by roads. Yet if you&#x27;re traveling in a city, you might say &quot;I walked 5 blocks.&quot; This is a linguistic shortcut, skipping implied information. If you&#x27;re trying to talk about both in a unclear context, additional words to clarify are required to sufficiently convey the information, that&#x27;s just how language words.

What a perplexing article.<p>Isn&#x27;t a pixel clearly specified as a picture element? Isn&#x27;t the usage as a length unit just as colloquial as &quot;It&#x27;s five cars long&quot;, which is just a simplified way of saying &quot;It is as long as the length of a car times five&quot;, where &quot;car&quot; and &quot;length of car&quot; are very clearly completely separate things?<p>&gt; The other awkward approach is to insist that the pixel is a unit of length<p>Please don&#x27;t. If you want a unit of length that works well with pixels, you can use Android&#x27;s &quot;dp&quot; concept instead, which are &quot;density independent pixels&quot; (kinda a bad name if you think about it) and are indeed a unit of length, namely 1dp = 158.75 micro meter, so that you have 160 dp to the inch. Then you can say &quot;It&#x27;s 10dp by 5dp, so 50 square dp in area.&quot;.

See also:<p>A Pixel Is Not a Little Square (1995) [pdf] – <a href="http:&#x2F;&#x2F;alvyray.com&#x2F;Memos&#x2F;CG&#x2F;Microsoft&#x2F;6_pixel.pdf" rel="nofollow">http:&#x2F;&#x2F;alvyray.com&#x2F;Memos&#x2F;CG&#x2F;Microsoft&#x2F;6_pixel.pdf</a>

Well the way I see them I don&#x27;t think they are a unit at all.<p>And the end pixels are &quot;physical things&quot;. Like ceramic tiles on a bathroom wall.<p>Your wall might be however many meters in length and you might need however squared meters of tile in order to cover it. But still, if you need 10 tiles high and 20 tiles width, you need 200 tiles to cover it. No tension there.<p>Now you might argue that pixels in a scaled game don&#x27;t correspond with physical objects in the screen any more. That&#x27;s ok. A picture of the bathroom wall will look smaller than the wall itself. Or bigger, if you hold it next to your face. It&#x27;s still 10x20=200 tiles.

&gt; A Pixel Is Not A Little Square!<p>&gt; This is an issue that strikes right at the root of correct image (sprite) computing and the ability to correctly integrate (converge) the discrete and the continuous. The little square model is simply incorrect. It harms. It gets in the way. If you find yourself thinking that a pixel is a little square, please read this paper.<p>&gt; A pixel is a point sample. It exists only at a point. For a color picture, a pixel might actually contain three samples, one for each primary color contributing to the picture at the sampling point. We can still think of this as a point sample of a color. But we cannot think of a pixel as a square—or anything other than a point.<p>Alvy Ray Smith, 1995 <a href="http:&#x2F;&#x2F;alvyray.com&#x2F;Memos&#x2F;CG&#x2F;Microsoft&#x2F;6_pixel.pdf" rel="nofollow">http:&#x2F;&#x2F;alvyray.com&#x2F;Memos&#x2F;CG&#x2F;Microsoft&#x2F;6_pixel.pdf</a>

The article starts out with an assertion right in the title and does not do enough to justify it. The title is just wrong. Saying pixels are like metres is like saying metres are like apples.<p>When you multiply 3 meter by 4 meter, you do not get 12 meters. You get 12 meter squared. Because &quot;meter&quot; is not a discrete object. It&#x27;s a measurement.<p>When you have points A, B, C. And you create 3 new &quot;copies&quot; of those points (by geometric manipulation like translating or rotating vectors to those points), you now have 12 points: A, B, C, A1, B1, C1, A2, B2, C2, A3, B3, C3. You don&#x27;t get &quot;12 points squared&quot;. (What would that even mean?) Because points are discrete objects.<p>When you have 3 apples in a row and you add 3 more such rows, you get 4 rows of 3 apples each. You now have 12 apples. You don&#x27;t have &quot;12 apples squared&quot;. Because apples are discrete objects.<p>When you have 3 pixels in a row and you add 3 more such rows of pixels, you get 4 rows of 3 pixels each. You now have 12 pixels. You don&#x27;t get &quot;12 pixels squared&quot;. Because pixels are discrete objects.<p>Pixels are like points and apples. Pixels are not like metres.

This isn&#x27;t just pixels, it&#x27;s the normal way we use rectangular units in common speech:<p>* A small city might be ten blocks by eight blocks, and we could also say the whole city is eighty blocks.<p>* A room might by 13 tiles by 15 tiles, or 295 tiles total.<p>* On graph paper you can draw a rectangle that&#x27;s three squares by five squares, or 15 squares total.

A pixel is a dot. The size and shape of the dot is implementation-dependent.<p>The dot may be physically small, or physically large, and it may even be non-square (I used to work for a camera company that had non-square pixels in one of its earlier DSLRs, and Bayer-format sensors can be thought of as “non-square”), so saying a pixel is a certain size, as a general measure across implementations, doesn’t really make sense.<p>In iOS and MacOS, we use “display units,” which can be pixels, or groups of pixels. The ratio usually changes, from device to device.

I think the author forgets that pixels inherently have both width and height, a single pixel, is inherently a 2 dimensional entity, whereas the meter is a purely one dimensional concept. You don&#x27;t usually talk about whether your meters are the same height as they are tall, or whether they&#x27;re taller than they&#x27;re wide.. because they don&#x27;t have those two dimensions.. You don&#x27;t talk about how your centimeters are arranged within your meter either.. (you can talk about how your subpixels are, and even if there are 3 or 4 of them).<p>So, I don&#x27;t think it&#x27;s entirely valid to talk about pixels as if they are pure, one dimensional units..<p>They&#x27;re _things_ and you can talk about how many things wide or tall something is, and you can talk about how many things something has. Very much the same way you can with bricks (which are mostly never square) (though tiles are, you never talk about how many kilotiles is in your bathroom either, yet you can easily talk about how many tiles wide or tall a wall is).<p>So, no, pixels is not a unit in the mathematical sense.. it&#x27;s an item, in the physical sense.<p>There are also things like scanners, that may have only one row of pixels on the scanner sensor, it does not have an area of zero, and you don&#x27;t need to specify that there&#x27;s one pixel on the other axis, because it&#x27;s an inherent property of pixels that they have both width and height and thus area in and of themselves.

So, the author answers the question:<p>&gt; That means the pixel is a dimensionless unit that is just another name for 1, kind of like how the radian is length divided by length so it also equals one, and the steradian is area divided by area which also equals one.<p>But then for some reason decides to ignore it. I don’t understand this article. Yes, pixels are dimensionless units used for counting, not measuring. Their shape and internal structure is irrelevant (even subpixel rendering doesn’t actually deal with fractions - it alters neighbors to produce the effect).

Pixel, used as a unit of horizontal or vertical resolution, typically implies the resolution of the other axis as well, at least up to common aspect ratios. We used to say 640x480 or 1280x1024 – now we might say 1080p or 2.5K but what we mean is 1920x1080 and 2560x1440, so &quot;pixel&quot; does appear to be a measure of area. Except of course it&#x27;s <i>not</i> – it&#x27;s a unit of a dimensionless quantity that measures the <i>amount</i> of something, like the mole. Still, a &quot;quadratic count&quot; is in some sense a quantity distinct from &quot;linear count&quot;, just like angles and solid angles are distinct even though both are dimensionless quantities.<p>The issue is muddied by the fact that what people mostly care about <i>is</i> either the linear pixel count or <i>pixel pitch</i>, the distance between two neighboring pixels (or perhaps rather its reciprocal, pixels per unit length). Further confounding is that technically, resolution is a measure of <i>angular separation</i>, and to convert pixel pitch to resolution you need to know the viewing distance.<p>Digital camera manufacturers at some point started using megapixels (around the point that sensor resolutions rose above 1 MP), presumably because big numbers are better marketing. <i>Then</i> there&#x27;s the fact that camera screen and electronic viewfinder resolutions are given in <i>subpixels</i>, presumably again for marketing reasons.

Happens to all square shapes.<p>A chessboard is 8 tiles wide and 8 tiles long, so it consists of 64 tiles covering an area of, well, 64 tiles.

A pixel is two dimensional, by definition. It is a unit of area. Even in the signal processing &quot;sampling&quot; definition of a pixel, it still has an areal density an is therefore still two-dimensional.<p>The problem in this article is it incorrectly assumes a pixel to be a length and then makes nonsensical statements. The correct way to interpret &quot;1920 pixels wide&quot; is &quot;the same width as 1920 pixels arranged in a 1920 by 1 row&quot;.<p>In the same way that &quot;square feet&quot; means &quot;feet^2&quot; as &quot;square&quot; acts as a square operator on &quot;feet&quot;, in &quot;pixels wide&quot; the word &quot;wide&quot; acts as a square root operator on the area and means &quot;pixels^(-2)&quot; (which doesn&#x27;t otherwise have a name).

<p><pre><code> But it does highlight that the common terminology is imperfect and breaks the regularity that scientists come to expect when working with physical units in calculations </code></pre> Scientists and engineers dont actually expect much, they make a lot of mistakes, are not very rigorous, not demanding towards each others. It is common for Units to be wrong, context defined, socially dependent and even sometimes added together when the operator + hasn&#x27;t been properly defined

Hopefully most people get that the exact meaning of &quot;pixel&quot; depends on context?<p>It certainly doesn&#x27;t make sense to mix different meanings in a mathematical sense.<p>E.g., when referring to a width in pixels, the unit is pixel widths. We shorten it and just say pixels because it&#x27;s awkward and redundant to say something like &quot;the screen has a width of 1280 pixel widths&quot;, and the meaning is clear to the great majority of readers.

A pixel is neither a unit of length nor area, it is like a byte, a unit of information.<p>Sometimes, it is used as a length or area, omitting a conversion constant, but we do it all the times, the article gives out the mass vs force as an example.<p>Also worth mentioning that pixels are not always square. For example, the once popular 320x200 resolution have pixels taller than they are wide.

Pixels are not measurement units. They&#x27;re samples of an image taken a certain distance apart. It&#x27;s like eggs in a carton: it&#x27;s perfectly legitimate to say that a carton is 6 eggs long and 3 eggs wide, and holds a total of 18 eggs, because eggs are counted, they&#x27;re not a length measure except in the crudest sense.

A bathroom tile is also a unit of length and area. A wall can be so many tiles high by so many wide, and its area the product, also measured in tiles.<p>It is just word semantics revolving around a synecdoche.<p>When we say that an image is 1920 pixels wide, the precise meaning is that it is 1920 times the width of a pixel. Similarly 1024 pixels high means 1024 times the height of a pixel. The pixel is not a unit of length; its height or width are (and they are different when the aspect ratio is not 1:1!)<p>A syntax-abbreviating semantic device in human language where part of something refers to the whole or vice versa is called a <i>synecdoche</i>. Under <i>synecdoche</i>, &quot;pixel&quot; (the whole) can refer to &quot;pixel width&quot; (part or property of the whole).<p>Just like the synecdoche &quot;New York beats Chicago 4:2&quot; refer to basketball teams in its proper context, not literally the cities.

This kind of thing is common in english, though. &quot;an aircraft carrier is 3.5 football fields long&quot;<p>The critical distinction is the inclusion of a length dimension in the measurement: &quot;1920 pixels wide&quot;, &quot;3 mount everests tall&quot;, &quot;3.5 football fields long&quot;, etc.

I’m surprised the author didn’t dig into the fact that not all pixels are square. Or that pixels are made of underlying RGB light emitters. And that those RGB emitters are often very non-square. And often not 1:1 RGBEmitter-to-Pixel (stupid pentile).

This depends upon who you ask. CSS defines a pixel as an angle:<p><a href="https:&#x2F;&#x2F;www.w3.org&#x2F;TR&#x2F;css-values-3&#x2F;#reference-pixel" rel="nofollow">https:&#x2F;&#x2F;www.w3.org&#x2F;TR&#x2F;css-values-3&#x2F;#reference-pixel</a>

This article wastes readers&#x27; time by pretending to command of a subject in a manner that is authoritative only in its uncertainty.<p>Pixel is an abbreviation for &#x27;picture element&#x27; which describes a unit of electronic image representation. To understand it, consider picture elements in the following context...<p>(Insert X different ways of thinking about pictures and their elements.)<p>If there is a need for a jargon of mathematical &quot;dimensionality&quot; for any of these ways of thinking, please discuss it in such context.<p>Next up:<p>&lt;i&gt;A musical note is a unit of...&lt;&#x2F;i&gt;

For those who programmed 8-bit computers or worked with analog video, a pixel is also a unit of time. An image is a long line with some interruptions.

A pixel is a sample or a collection of values of the Red, Green, and Blue components of light captured at a particular location in a typically rectangular area. Pixels have no physical dimensions. A camera sensor has no pixels, it has photosites (four colour sensitive elements per one rectangular area).

Reminds me of this Numberphile w&#x2F; Cliff Stoll [1]: The Nescafé Equation (43 coffee beans)<p>[1] <a href="https:&#x2F;&#x2F;youtu.be&#x2F;3V84Bi-mzQM" rel="nofollow">https:&#x2F;&#x2F;youtu.be&#x2F;3V84Bi-mzQM</a>

Also a measurement of life. Back in the 320x200 game days, when playing something with a health bar, we used to joke that someone had one pixel of life left when near death.

A Pixel is a telephone.

Pixel is just contextual. When you are talking about one dimensional things it&#x27;s a unit of length. In all mother cases it&#x27;s a unit of area.

Or perhaps it&#x27;s multivariate and there&#x27;s no point in trying to squish all the nuance into a single solid definition.

The pixel ain&#x27;t no problem.<p>A &quot;megapixel&quot; is simply defined as 1024 pixels squared ish.<p>There is no kilopixel. Or exapixel.<p>No-one doesn&#x27;t understand this?

Should be pixel as area and pixel-length as 1-dimensional unit.<p>So an image could be 1 mega pixel, or 1000 times 1000 pixel-lengths.

This is a fun post by Nayuki - I&#x27;d never given this much thought, but this takes the premise and runs with it

Pixel is also a unit of a phone.

The author is very confused.

Wait till they hear about fluid ounces.