Resizing Photos Without Artifacts

[ElNico]

For the record, I looked up what jpeg artifacts actually are and what causes them, and that has not helped me to answer this question. My apologies if this is a really dumb question.

Say I have a jpeg image fresh off my camera, and I want to reduce the file size so that I can upload it somewhere (including but not limited to this forum). If I open the file in MS Paint, resize it by 50% in both directions (so the image is shrunk overall by a factor of 1/4), and re-save it as a jpeg, does that cause any loss in quality OTHER than removing three-fourths of the pixels?

If yes, then how can I reduce the file size of a jpeg image without corrupting it (beyond the obviously-unavoidable reduction in resolution)? Do I just need to be using more sophisticated software than Paint? I obviously don't intend to use Paint for any "real" photo editing; I'm just wondering whether using something else is necessary for this particular problem. The Windows 10 "Photos" app appears to be able to crop a jpeg without introducing artifacts (thank goodness), but it doesn't resize.

If no (or perhaps "no you idiot, why would you even think that"), then what kind of editing and re-saving does introduce jpeg artifacts? I've always avoided them simply by saving edited images in any format other than jpeg - even if the image was a jpeg to begin with - usually png; but that doesn't work when resizing an image to reduce the file size, since png has a higher data density than jpeg.

 

[KmH]

What JPEG artifacts are produced by re-interpolation to reduce the file size depends on the interpolation algorithm used.
Most decent editing apps offer several interpolation algorithms to choose from.

The easiest way to reduce the file size is to reduce the QUALITY setting value in the SAVE function of your editing app. Doing so does not change the size of the image.
For display here on TPF image quality does not degrade by lowering the QUALITY setting when saving the image.
You have to crop, or physically delete pixels to change the image size (resolution).

Note: Edit a copy of the original and start with a RAW file if possible.