Not sure the size requirements for this site, but there's a popular image editor program for free called GIMP. It works in a bind if you're not that into image editing software. Plenty of tutorials to chane what you need too. You can use this in place of the multiple online resources in case you're worried about privacy when resizing images.
I'm aware of how to fix the problem from the uploader's end (I don't upload photos anyway). But it is surprising that a website wouldn't be coded to resize images to properly display them. It's a bit broken.