Is this not outdated?<p>It uses examples of how pixels on scanners, printers, and CRT monitors are not squares. Fair enough. Back when this was written, one could very reasonably argue that pixels were intended to be point samples with a convolution.<p>But modern pixels on most LCD screens certainly are exceedingly crisp squares (with subpixels), and processing RAW camera sensor data, antialiasing techniques, and image resampling seems to "mostly" assume that pixels do represent the average color over a square rather than a point sample. Not <i>perfectly</i>, but as a reasonable first-order approximation.<p>I understand that 25 years ago it might have been reasonable to argue that pixels aren't squares.<p>But today... aren't they, at least as a first-order approximation? (With some further adjustments to avoid antialiasing artifacts, desired sharpness, and so forth.)<p>The idea that pixels are primarily point samples seems far <i>more</i> misleading -- as if they were analagous to audio samples which <i>are</i> point samples as a first-order approximation, but pixels are <i>nothing</i> like audio samples.
As a pixel art artist, I certainly see pixels as little squares. As a 3D programmer working with 2D point-sample textures, I do not see pixels as little squares. So the answer to whether or not a pixel is a little square is, like so many of life's questions, not a simple yes or no, but rather, it depends.
I can't help but think of the famous humpty dumpty quote<p>> When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to mean—neither more nor less." "The question is," said Alice, "whether you can make words mean so many different things." "The question is," said Humpty Dumpty, "which is to be master—that's all."<p>The fact is that pixels don't have a well defined meaning. Some people use them as squares, some people use them as samples. Then you get into subpixel font rendering, where you quite explicitly acknowledge the screen as master, and you design your image for a desired result.<p>So yeah it's an ecosystem of people doing different things with different interpretations, and trying to mostly play nice with each other.
This is important point indeed. Here is what helps myself, when thinking about pixels.<p>- pixels are point samples in 2D space
- their position is exact
- position of of top-left point is (0,0)
- position of bottom right is (cols-1,rows-1)<p>This way all math work (subsampling, affine or perspective warps, lens distortion, or even warping between image and any layer neural network). Failure to do that, will cause subtle issues that will degrade your performance. These will become quite important when working
with pixel accurate methods (3d object tracking, object detection in tiny resolutions and 1-1 mapping between OpenGL and Neural Network). So I have to agree, pixels are not tiny squares, they are dots in 2d space.
One of the weird experiences I had in college was working for the paper in the 90s. We has desktop publishing but the photos for the paper were taken out back to a machine with a screen copied them into solid black dots of various sizes. They were waxed onto printed newspaper pages and wisked off to the printer.<p>I often wondered how you would reproduce it digitally but apparently I was thinking about it wrong.<p>Halftone is the term
<a href="https://en.m.wikipedia.org/wiki/Halftone" rel="nofollow">https://en.m.wikipedia.org/wiki/Halftone</a>
Pixels, at least when they come from cameras or need to be mapped to a 3D world, are still not square.<p><a href="https://doc.visionappster.com/3.0-beta5/engine/world-coordinates/#pixels" rel="nofollow">https://doc.visionappster.com/3.0-beta5/engine/world-coordin...</a>