Held: Wednesday, 18 February 2015

Back to Outline 17 - Homogeneous Lists: Making and Manipulating Groups of Drawings . On to Outline 19 - Conditionals.

Summary

We continue our synthesis of algorithms and image making as we explore techniques for programming with the basic GIMP tools.

Related Pages

• Reading: The GNU Image Manipulation Program
• Reading: Programming the GIMP Tools
• Lab: Scripting the GIMP Tools
• Morning EBoard 18 (Source a.m. 18)
• Afternoon EBoard 18 (Source p.m. 18)

Overview

• A new model of images making.
• Coding algorithms for drawing.
• Other useful techniques.

Administrivia

• New partners!
  • One set of cards for people who want to work alone on HW 5.
  • One set of cards for people who want a partner.
  • Cross your fingers that things work out.
• Review sessions at 9am (Ajuna) and 8pm (Alex) on Thursday.

Upcoming Work

• Homework 5.
  • Due next Tuesday at 10:30 p.m.
• No Lab Writeup for Today
• Quiz Friday: Anonymous procedures, Booleans, RGB Colors, Color transformations
• Reading for Friday
  • Conditionals

Extra Credit Opportunities

Academic

• Pioneer Diversity Council Diversity Dialogue, 8:30 p.m. 26th, Main Quad "Academic Athletes and Academic Students". Note new date!
• Any two talks from TEDx Grinnell, February 21, 1-5 pm. Live stream at http://tedxgrinnell.com.

Peer Support (Morning Section)

• Julia's radio show, "The Hot Box". Wednesday night/Thursday morning 1:00-2:00 a.m.
• Host a prospie.

Peer Support (Afternoon Section)

• Men's Basketball vs. Knox, Wednesday at 7:30 p.m., New Darby
• Spring new year event, Feb. 21 5:30-7:30 in Harris

Other Good Things

• Women's Basketball vs. Knox on Wednesday.

Models of Images

• As we've seen in our early discussions, there are many ways to think about an image.
• In our first explorations with the GIMP, we looked at an imperative, tool-based model of drawing.
  • The model is imperative in that it consists of a sequence of commands (do this, then this, then this).
  • The model is tool-based in that almost all operations involve selecting a tool and then applying that tool.
• Over the next few weeks, we'll see a variety of other models.

Encoding Drawing Cmmands

• Because there are only a limited number of basic actions one can perform in GIMP, it is possible to represent each of these actions as a procedure.
• These procedures are parameterized in that you can modify how they work by providing different input values.
• Many of these procedures change the state of the system. When procedures change things (as opposed to computing new values), we tend to suffix their name with an exclamation point.
• For clarity, we tend to prefix the name of a procedure with the kind of value it works on. For example,
  • procedures that modify and create images begin with image-,
  • procedures that modify the global context begin with context-,
  • procedures that modify and create colors begin with color-.
• The primary model we use is to repeatedly select and then stroke or fill regions.
• We do not expect you to remember all of these procedure names.
  • One of the flaws of the current strategy for teaching 151 is that there are way too many procedures to remember.
• There is (or should be) a convenient reference menu in MediaScheme.
  • There is also a convenient reference section on the Web site.
• If there's something that you want documented, bug me.

Lab

• Work on the labthe lab.
• Be prepared to reflect on some of the questions contained therein.