Laptop/Notebook is cropping all desktop images

my laptop/notebook was open yesterday but no programs were running. i closed the laptop without shutting it down and reopened it about 2 hours later. the image that was originally saved as the desktop/wallpaper in full screen was now cropped. why is this happening? every image i now save as desktop/wallpaper is saved in this cropped version. i now have to manually go back in and change it. how can i get this corrected?