You can crop and resize the image to whatever size you want with most photo software. If it's not a person or animal, stretching the image a little usually is not noticeable.
uh.. thanks, mike... yea... I know! I have photoshop, gimp, lightroom, helicon and a host of others.... and have been messing around with image editing since I first got a computer.. and that was in the 70's. So I have a pretty good idea of what I can and can't do. I am not a photoshop guru, for sure... but as far as the basics go... no problem.