Sample Image 1:
Same image at twice the size:
While not too bad, the image definitely lost some quality.
Making pictures wider is also similar to make an image bigger. In this case you want to control an images dimensions specifically by one dimension. The key here is to maintain the ratio of the size. There are two ways to do that.
Shrinking a photo relies on the same type of scaling used above, except that in this case you’re trying to lower the percentages of teh size. Again similar to the above the image willget sized down by a specific ratio. So if it’s 1600 x 1600 scaling by 50% would get you to 800 x 800. (1600 * .5)
Altering the sizes of images is a tricky business. Although I want get to far into the math behind it, or how specific screen sizes can affect things, it is important to realize that any image you see is a bunch of code on a computer, that gets translated by whatever screen you see it on. So however similar a photo will to the real thing, it’ll never look exactly the same, and similarly, as you alter the sizing of an image things will change slightly. Checkout the image resolutions below. You might be familiar with with terms like 720P, 1080P, and 4K. But each of those resolutions is actually made up my tiny individual dots. If you look at the below image you’ll see what I mean.
Now all three screens can display the same image, but the one above cannot go into as much detail as a 4K image could. At the same time an image that is tiny, say 1600 x 1600 pixels that gets stretched out onto a 4k screen will look terrible. But it likely won’t look as bad at 720P even though that screen is more grainy.
The next thing that matters if Points Per Inch, PPI, or Dots Per Inch, DPI. Now PPI typically refers to printing. But in a similar manner to the screens above, a lower PPI will result in a grainier image. If you step back and look at the above Ks from across the room you probably won’t notice much difference. Much of that has to do with the fact that your brain will adjust the image, but there is also a maximum amount of resolution your brain can perceive
The standard DPI for the web is 72 DPI. (So a screen that was 720 pixels wide back when there were CRT tubes would have been 10 inches wide. Now for print the standard PPI is 300. (Anything less than that will feel grainy to you since you’re used to better). Interestingly many mobile devices have gone base this level of DPI.
So even though a screen may have more pixels it may not look sharper.
Imagine in the below image that you’re trying to display that picture, in a “higher resolution” screen there are just more pixels for display, but while total pixels matter so do the density of them. Because at a higher density even a smaller screen in terms of total pixels will look sharper.
All of the above is important for image editing because the program above will have to do some sampling to determine what pixels to choose and keep when going from small to big, big to small, or anywhere in between. So keep in mind that quality might be affected some.
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