Non straight geometrical shapes (i.e. diagonal lines, curved lines or circles) created with MS paint appear to me pixelated.
For example, if I create a jpeg or png 100px X 100px raster image with a White background containing a diagonal line (without hitting shift while doing so), that diagonal line would appear to me pixelated.
If it doesn't happen with programs such as Adobe Photoshop what is the way to explain this? (Lack of anti-aliasing perhaps)
What is the way to explain this?
Different anti-aliasing algorithms.
Let's understand what anti-aliasing is. It is rendering a pixel with an intermediate color that is between two zones of different colors.
If you do not have any antialiasing at all, you will have some pixels of one color and some of another.
Some "fast anti-aliasing methods could just give some pixels the exact intermediate value of some colors.
And some other algorithm could render more gradation of colors, making the border smoother.
Sometimes the algorithm must make several calculations to do this. For example in a 3D game, you could choose to make several passes to smooth borders more and more. You could choose 1 pass (second image) or several passes (third image)
One note. If you are working at 100% that effect, or more likely defect, is NOT pixelation, it is aliasing or saw borders.
I cant answer for all aplications. Different applications use different methods.
Essentially Photoshop has 2 methods:
When stroked draws circles that have a blurred border and stamps them not too tightly (if you stamp them too tightly you will burn out the blur). While Paint stamps even blurred circles too often, or does not have blurred edges.
This blur will be interpreted as anti-aliasing. But since aliasing is caused by a signal that has a too high frequency to be reproduced by the discretisation step. If you now have something that never had any frequencies that exceeded your ability to reproduce are you anti aliasing? Debatable. But you may also equate a too blurred edge as a better one, in which case its definitely not AA.
But then Photoshop can also draw vector art, in these cases Photoshop just renders the lines at super resolution and samples them down for AA.
Though there's significantly better ways to do this too.
You can do the same as the later in paint if you wish. Just draw a a image thats say 4-16 times larger then scale it down. Although the sampling filter paint uses is tuned to be more ringing than any of the options of PS save nearest neighbor. I dont see any reason to use paint though.
