I wish my wordpress image uploader to be able to make thumbnails of any image sz

I’ve found the place in my wordpress admin code where thumbnails
sizes are defined, and it works great! I think I found the fix on this
wordpress.org site, in fact.

NOW I would like this thumbnail creator to work for ALL images,
not just images that at 1024px max. I found the place where this
is defined, but aparently whatever it is in wordpress that is
resizing these images just cannot handle any image that is larger.

Is there some freeware or supercode that can help wordpress get over this hurdle?

thank you in advance