CSC151 2010S, Class 05: Programing the GIMP Tools

Overview:
* Reflection.
* A model of images, extended.
* Coding algorithms for drawing.
* Other useful techniques.

Admin:
* I feel particularly embarassed to say this, given that one of you mentioned procrastination as your least favorite thing about Grinnell, but I have not yet finished going over your HW1's and your quizzes.
* Does anyone need a partner for HW2?
* Are there any questions on HW2?
* What do you do when you see large chunks of code, as in the reading for today?
* We'll spend a few more minutes debriefing on Friday's lab.
* EC for Friday's CS table at noon in the Day PDR in the JRC on Pair Programming.  (More info to follow later.)
* Two readings for Tuesday: Numeric Values & Symbolic Values.
* Rank Strangers concert this Friday night.  (No extra credit, but your classmate encourages you to attend.)

Reflection:
* What did you learn on Friday?
  * The basics of programming in Scheme
  * Instructions seem to begin and end with
    parentheses.
  * image-load and image-show were introduced
  * Learned how to create libraries.s
* Best part (if there was one)?
  * It's interesting that we put operations
    at the front, rather than in the middle,
    and parentheses don't surround operands
  * define and operations are pretty cool
* Worst/hardest/most confusing?
  * Some instructions didn't work, and no one
    could help.
  * What's the diff between the interactions and
    the definitions pane
    * The definitions pane is intended for
      longer-term stuff (things you want to
      save or remember)a
    * The interactions pane is intended for
      experimentation
    * Definitions in the interactions pane
      go away when you hit Run again
    * Non-definitions in the definitions pane
      get executed every time you hit Run
  * We need to warp our brain a bit to deal
    with prefix notation.

A Model of Images:
* There are lots of ways we can describe an
  image.
  * Some algorithms are imperative - a sequence
    of instructions (do this, then that, then
    something else)
  * Some are declarative - This image is composed
    of a blue circle and ...
  
* GIMP Tools: Write a series of instructions
  that model how a human builds an image with
  the GIMP.

Coding Drawing Operations in Scheme:
* (image-select-ellipse! ____ ___ ___ ___ ___)
* (image-fill! IMAGE)

Lab: