(if (= imageType GRAY) (do-greyscale-stuff) ;; if grayscale (do-color-stuff) ;; else )
(if (= imageType GRAY) (do-greyscale-stuff) ;; if grayscale (do-color-stuff) ;; else )
So you have a list that starts with if; then you have the condition; then the if clause, then the else clause.
Everything uses prefix notation, so instead of asking if imagetype equals grey, you say if equals imagetype grey.