I'm reading some articles about pixels and I encountered this question.

First. When my photo is 20x20, and I'm seeing it at 100%, every pixel of photo is shown with every pixel of monitor.

When I zoom in, for example, 2000%, It's 20 times the 100% image. so every pixel of image occupies 20 pixel of monitor.

But What happens when you zoom-out? for example 50%. every two pixel of image occupies one pixel of monitor? If so, every pixel is capable of one solid color. not Two. Right? Can you explain it!?

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  • I think that it starts to merge pixels (that's why it becomes blurry/reduced quality) – WELZ Dec 6 '17 at 13:42
  • Keep in mind the important difference in definitions. Pixels don't have a size. The physical elements that make images on a monitor -- say "dots" -- DO have a size. Monitors have a "dot pitch" (size measurement). Do not confuse real, physical elements of an imaging device with "picture elements" (pixels) of a digital image. .25mm is a common monitor dot pitch. – user8356 Dec 6 '17 at 18:55
  • I made a 10x10 picture in Photoshop. Selected every pixel and color it differently and zoomed 50%. Then opened Magnifier. And looked closely. Yep. Colors changed and I think merged. Thank you again. – Messi.Meysam Dec 7 '17 at 7:35

The program used can do two basic types of calculations.

  1. Discard one 1 of every 2 pixels (or whatever proportion you have 2/3, 3/5) That is a really fast approach but produces saggy edges.

  2. Average the values of each pixel, using different types of operations. This takes some milliseconds, depending on the image and type of operation done.

This two processes can be done either only displaying the image, or actually resampling it.

Actually, this type of operations are done not only on downscaling, but also when upscaling them. For example when you choose a non-exact proportion like 175% or when the image viewer has an option to resample instead of just zooming.

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