1 Basics

The teachpack assumes working knowledge of the basic image manipulation primitives and introduces a special kind of image: a scene.

Scene

(define (focus-at-0-0 i)

(and (= (pinhole-x i) 0) (= (pinhole-y i) 0)))

(and/c image? focus-at-0-0)

The teachpack can display only Scenes, which are images whose pinholes are at position (0 ,0).

(empty-scene width height) → Scene

width : natural-number/c

height : natural-number/c

Creates a width x height Scene.

(place-image img x y s) → Scene

img : image?

x : number?

y : number?

s : Scene

Creates a scene by placing img at (x ,y) into s; (x ,y) are comp. graph. coordinates, i.e., they count right and down from the upper-left corner.