Overview

• Preliminaries.
  • Admin.
  • Upcoming work.
  • A few notes from yesterday's class.
  • New homework assignment.
  • Questions.
• Questions on the reading.
• Lab.

Preliminaries

Admin

• I won't be able to hold a review session this week. Sorry.
• Extra credit:
  • Falling Club, 4:15-6:15 at the rock wall.
  • Thursday extra, Thursday @ 4:30 p.m., Sci. 3821, Red/Black trees.
  • Opera Iowa: The Elixir of Love, Thursday, 7:30, Roberts
  • CS Table Friday @ noon: Law, Order, and Computers

Upcoming work

• Start homework 4
• Friday's reading: The GNU Image Manipulation Program and Scripting the Gimp Tools
• Lab writeup: Exercise 5
  • Subject: CSC 151.02 Writeup 11: Lists of Drawings (YOUR NAME)
  • Due Friday.

A few notes from Tuesday's lab

irgb-redder and related procedures are not always invertible. Consider what happens at the extreme values.

> (define red1 (rgb-new 244 0 0))
> (define red2 (rgb-new 255 0 0))
> (define red3 (rgb-new 250 0 0))
> (define black (rgb-new 0 0 0))
> (define very-dark-grey (rgb-new 8 8 8))
> (define very-dark-purple (rgb-new 8 0 8))

What do you think about the following procedure?

(o irgb-complement irgb-redder irgb-complement)

How would you implement irgb-redder? (There's how it's implemented, and what we might do given what we've learned in using it.)

• Current implementation

  (define irgb-redder (lambda (irgb) (irgb (+ (irgb-red irgb) 32) (irgb-green irgb) (irgb-blue irgb))))

  (define irgb-redder (lambda (irgb) (irgb (+ (irgb-red irgb) 24) (- (irgb-green irgb) 16) (- (irgb-blue irgb) 16))))

About homework 4

• New partners!
• Four problems, all emphasizing transformations.

Questions on the Readings

• Nope.

Lab