CSC151.01 2015S, Class 14: Transforming Colors

Overview

Preliminaries

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.)
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

Diversity Dialogues, February 19: 8:30 p.m. in Main Quad, sponsored by Pioneer Diversity Council. ("Indoor Quidditch Matches"?)
TEDx Grinnell, February 21

Swimming, Conference Championships, February 13-15, The Osgood
Track and Field, Saturday, the "No one has donated the requisite $1mil to name this space" field house.
Men's Basketball vs. Knox, next Wednesday at 7:30 p.m., New Darby
Noteworthy fundraiser

Remember:

(image-show canvas) and (image-show canvas) will create two windows on the same images, not two images.
GIMP hates to show updates, so you may need to force it to.

Why use

(image-set-pixel! canvas 0 0 
                  (irgb-darker (image-get-pixel canvas 0 0)))

rather than

(image-transform-pixel! canvas 0 0 irgb-darker)

Because we can shift pixels

(image-set-pixel! canvas 2 3 
                  (irgb-darker (image-get-pixel canvas 3 2)))

Or change images

(image-set-pixel! canvas 2 3 
                  (irgb-darker (image-get-pixel savnac 3 2)))

Why are

(irgb-complement (irgb-darker fave1))

and

(irgb-darker (irgb-complement fave1))

different?