sharpen vs flatten

sharpen and flatten both are verbs.

Word	Noun	Adjective	Verb	Adverb
sharpen	No	No	Yes	No
flatten	No	No	Yes	No

sharpen (verb)	flatten (verb)
become sharp or sharper	become flat or flatter
make crisp or more crisp and precise	make flat or flatter
raise the pitch of (musical notes)	lower the pitch of (musical notes)
put (an image) into focus
make (one's senses) more acute
give a point to
make sharp or sharper
make (images or sounds) sharp or sharper