Held: Tuesday, 1 March 2016

Back to Outline 21 - Anonymous Procedures, Revisited. On to Outline 23 - Revisiting Lists.

Summary

We consider a simple approach to working with images - looping over the positions in an image and computing a new color based on positional information. We then explore some applications of this approach.

Related Pages

• Reading: Building Images by Iterating Over Positions
• Lab: Building Images by Iterating Over Positions
• EBoard 22 (Source 22)

Overview

• Models of images.
• Iterating over positions: Images as functions from position to color.
• Blends and other positionally-computed images.
• Drawing simple shapes.
• Some strange computations.

Administrivia

• Continue partners!
• Prof. Curtsinger will be teaching class for the rest of the week.
  • If anyone wants to take notes for eboards, I'll provide extra credit.
• I'm sorry that I can't be here for today's class; it's one of my favorite topics of the semester. I hope you have fun!

Reminders

• No more office hours this week.
  • I'll do a lot of email or text Q&A this week.
• Tutor hours
  • Sunday, 3-5 p.m.
  • Sunday-Thursday, 7-10 p.m.
• Weekly review sessions:
  • Wednesday at 8pm in the CS Commons with
  • No Thursday review session this week .... )-:
  • Thursday at 8pm in the CS Commons with

Upcoming Work:

• Reading for Tuesday
  • Building Data Structures with Heterogenous Lists
• Assignment 5 due TONIGHT at 10:30 p.m.
• Exam 2 to be distributed on Wednsday.
• Lab Writeup: Exercise _
  • Send email titled CSC 151 Lab Writeup 22 (Your Names)
  • Do not include the underscores.
  • Send to CSC151-02-grader@grinnell.edu
  • Due before class on Friday.

Extra Credit

• Send your reports to rebelsky@grinnell.edu with subject "CSC 151 Extra Credit". (Do not include the quotation marks.)
• Send opportunities to me before class with subject "CSC 151 EXTRA CREDIT OPPORTUNITY!"

Academic / Artistic

• Met Opera Simulcast, Saturday, March 5.

Peer

• Pub Quiz Wednesday at 10, hosted by Neuro/Psych SEPC. You can eat food, or pay to participate in the quiz ($3/team).

Regular Peer

• Social Dance Workshop Tuesdays 7:00-8:00 in Bucksbaum Dance Studio
• Pun club Saturdays at 4pm in Younker
• Electronic Potpourri on KDIC Fridays at Five
• Space Odyssey KDIC Fridays at Six

Misc

• Christine Tran show in Smith Gallery.
• Thursday evening Pub talk on Plans - Grinnell's own contribution to social media

Far in the Future

• Lords of the Flies, April.

No Extra Credit, But Still Good

Models of images

• We've seen a variety of models of images.
  • Images that we describe by composing basic shapes.
  • Images that we create by transforming existing images.
  • Images that we create by using the Gimp tools.
  • Images that we create by a combination of techniques.
• But there are certainly other models of image making. We'll learn at least two more this semester.
• Why are we learning so many models of image making? Because the basic operations you have affect the way you think about problem solving.

The image-compute model

• In the image-variant model, we built images with a starting image and a function from colors to colors.
• We will consider a variant of this model - images as functions from positions to colors.
• That is, given an (x,y) pair, use a function to determine a color for the pixel at (x,y).
• Syntax: (image-compute *function* *width* *height*)
  • No exclamation point because we are not changing anything that alread exists; we are simply computing a new image.

Examples

• Color blends are the most natural thing to make.
• We can also make shapes by using conditionals.
• Given that colors are just numbers, we can also just do numeric computations and see what they give us.