# Prelude ## Colors ### Compare two Colors Use: `(if (color-eq (255 200 0) (200 255 0)) "yes" "no")`. ``` (defn color-eq (a b) (and (eq a:0 b:0) (eq a:1 b:1) (eq a:2 b:2))) ``` ## Pixels ### Erase all pixels of a specific color Use: `(pixels erase-color (255 0 0))`. ``` (defn erase-color (a b) (a:0 a:1 a:2 (if (and (eq a:0 b:0) (eq a:1 b:1) (eq a:2 b:2)) 0 255))) ``` ### Posterize Use: `(pixels posterize 40)`. ``` (defn posterize (a q) ( (step a:0 q) (step a:1 q) (step a:2 q) a:3)) ```