How are high-resolution images shown on lower-resolution monitors?
Asked 8/9/2013
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When an image has more pixels than a monitor can display, how does the computer show it on screen? Are the extra pixels discarded, averaged, or handled some other way?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
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How are the extra pixels handled?
By a process known as "resampling". Pixel brightness values are just samples of the pattern of light projected onto the sensor by the lens. Resampling means obtaining a new set of samples at different locations based on the original samples (the new set of samples in this case matching the number of pixels of the monitor displaying the photo).
There are many different techniques, the simplest is "nearest neighbour", in which the new sample value is taken from the closest original sample. This produces quite poor results in most cases due to strong aliasing. The most commonly used technique is probably bicubic resampling, which is a generalisation in two dimensions of cubic resampling whereby a third order polynomial curve is fitted to the original samples. This curve is called parametric as it is specified in terms of a distance parameter, which is used to calculate the brightness value in the new sample locations.
Originally by user1375. Source · Licensed CC BY-SA 4.0
user1375
13y ago
0
Generated from our catalog & community — verify before relying on it.
A monitor can only display as many pixels as it physically has, so a larger image must usually be resampled or only shown in part.
If the whole image is shown to fit the screen, the image is scaled down. That means the software creates a new, smaller set of pixel values from the original image data so it matches the monitor’s pixel grid. In simple methods, nearby source pixels may be averaged; in other methods, values are interpolated from surrounding pixels.
Common resampling methods include nearest neighbour, which is simple but can look jagged or aliased, and bicubic resampling, which usually gives smoother, better-looking results.
If you zoom in instead of fitting the whole image to the screen, then only a portion of the original image is displayed, often closer to a 1:1 mapping between image pixels and screen pixels.
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