CSC151 2009F, Class 12: Transforming Colors

Admin:
* Tuesday seems to be a hard day to remember.
* Lab Writeup 3 distributed.  
  Transforming RGB Colors, exercises 5-7.
* Exam 1 distributed.
  A quick runthrough
  Time each class for discussion
* Reading for Friday: Transforming Images.
* Don't forget the Grinnell HS Homecoming Parade tomorrow @ 5:30 downtown.
* I hear the play is in need of more male actors.  
  Even if you're an extra, you get to hang with the way cool cast.
  Today is the last day for tryouts.
* EC/Academic: 
  * Gene Gaub plays Brahms.  11 a.m. Thursday, Herrick.
  * Dennis Vaccaro '11 presents 
      Graphical User Interface development using the Qt toolkit
    Thursday, 3821, at 4:30.  
    Refreshments at 4:15 in commons.
* Any EC/Support?
  * Women's soccer Saturday
* EC/Other
  * Gender Neutral Forum Thrusday at 8:00 p.m. in Forum South Lounge
* Thoughts or questions on yesterday's lecture?

Overview:
* Review: Color basics.
* Computing new colors from old.
* An example.

Need a way to represent colors so that the computer "understands"
* Mechanics: RGB
* Three component: Red, Green, and Blue
  * Real number between 0 and 1
  * In this class, integer between 0 and 255, inclusive

* Create new colors (rgb-new red green blue)
* Set and get pixels
  (image-set-pixel! image col row color)
  (image-get-pixel image col row color)
* Get components
  (rgb-red color)
  (rgb-green color)
  (rgb-blue color)

Today (and beyond): Transforming colors
* Color transformations help us understand colors better
* Once you can transform colors, you can transform images

What does a color transformation look like?
* Set of predefined transformations
  rgb-darker
  rgb-lighter
  rgb-redder
* Our own transformations
(define color-transformation
  (lambda (rgb)
    (rgb-new ___
             ___
             ___)))
* We have some fun with harry


LAB

* Skip exercise 4
Lab!