How do I resize/change resolution of pictures easily? I just tried to make a post on another StackExchange site, but unfortunately, when I tried to take a picture of the problem, I got an error that the image must be less than 2 MB to upload it to StackExchange! The edit button on my Android photos app lets me draw over, crop, change tint/brightness/contrast, and add lots of WACKY EFFECTS to my pictures, but I can't figure out how to shrink the resolution! Thanks in advance.
I'm not aware of any "native" or "pre-installed" capabilities. But the easiest way, if you need it more than once a year, is to use a suitable app. You can find some candidates in my app-listing Other photo editors. Examples:


JustResizeIt! allows to resize single images or entire batches. Comes for free, size less than 1MB, decent permissions (access storage and internet only).
Image Shrink Lite is even smaller (less than 400k), and additionally allows you to remove Exif data (location etc.) No network permissions requested, just read/write storage. Free again.


Both mentioned apps also have paid counterparts; I didn't check the differences between those versions. For more candidates, see the list linked above :)