• New partners!

Overview

• Preliminaries.
  • Admin.
  • Upcoming Work.
  • Extra Credit.
  • Questions.
• Lab.

Preliminaries

Admin

• Mentor session tomorrow at 8:00 p.m.
• Review sessions tomorrow at 9:00 a.m. and 1:15 p.m.
• No quiz Friday!
• Using the virtual machine requires that you read the instructions.
• Three parts to every question.
  • Your code
  • Your command in the interactions pan
  • Error message or description of problem

Upcoming Work

• Exam 1.
  • Exam due in electronic form due last night at 10:30 p.m. (free extension until tonight at 10:30 p.m.).
  • Exam due in printed form TODAY (free extension until Thursday at review time).
  • Required epilogue due TONIGHT at 10:30 p.m. (free extension until TONIGHT at 11:00 p.m.)
  • I'll collect printed exams now for those who have finished. For those who haven't, bring them to review session tomorrow or slip them under my office door before then.
• No lab writeup for today (no matter what it currently says online)
• Reading for Friday
  • Boolean Values and Conditionals
• HW4 due next Tuesday (to be distributed later tonight): Color and Image transformations
  • You will write color transformations, like you are doing in class today.
  • You will learn how to apply them to images.
  • Your partner is your lab partner from today's class

Extra Credit Opportunities

Academic

• TEDx Grinnell, February 21

Peer Support (Morning Section)

• Julia's radio show, "The Hot Box". Wednesday night/Thursday morning 1:00-2:00 a.m. Musicals. TONIGHT
• Swimming, Conference Championships, February 13-15, The Osgood
• Track and Field, Saturday, February 14, the "We Don't Yet Have a Million Dollar Donor Who Wants to Name a Gym" Field House

Recommended, But no EC

• 2 <3 GC day next Wednesday.

Questions

How should I notate how long each problem took?

Something like

    ; Problem 2
    ; 30 minutes

I've seen students write

    ; Problem 2
    ; Started at 11:10:05, stopped at 11:21:14.  Restarted
    ; at 11:55:01.  Stopped at 11:55:02.  My head hurts.
    ; ..
    ; Total of fifteen minutes and 11.5 seconds.

Lab

Debrief

• Since you can't have a component greater than 255 or less than 0, some of the transformations are capped and therefore don't work quite as you think they should.
• Yes, we are once again in a world in which procedures do not change their parameters.
  
  • (irgb-redder mycolor) does not change mycolor.
• Yes, we are once again a world in which the order in which we apply procedures can matter.
  • (irgb-darker (irgb-complement mycolor)) is not the same as (irgb-complement (irgb-darker mycolor))

• Why use

  (image-set-pixel! image1 0 0
                    (irgb-redder (image-get-pixel! image1 0 0)))
  

  • Because we don't need to use the same image or position

    (image-set-pixel! image1 0 0 (irgb-redder (image-get-pixel! image2 0 0)))

    (image-set-pixel! image1 2 3 (irgb-redder (image-get-pixel! image1 3 2)))