Outline 18: Programming the GIMP Tools

Held: Monday, 29 September 2014

Summary

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

Related Pages

Overview

Administrivia

Continue partners from Friday.
Welcome to any prospective students we may have!
Office hours (modified due to meetings):
- Monday 3:15-4:45
- Tuesday 8:00-9:45
- Wednesday 8:00-9:45
- Thursday 8:00-9:45, 2:30-3:15
- Friday 1:45-3:15 (also Walking hours 1:15-1:45)
Let me know by 5pm today if you want to work alone on the next HW.
Reflections on partners.
- I appreciate the thoughtful comments I've received.
- Some feel very strongly that letting some people choose partners will disadvantage those who don't choose their own partners.
- Scheduling is a problem.
- One person suggested "No partners, but you can talk to anyone". I worry that this model means that some people will be much slower than others (partnering does help even things out).
- One person suggested that groups make a policy that you rotate who is at the keyboard.
- Would pairs rather than groups of 3 be better for scheduling?
To provide you with incentive to take your own notes on each topic we cover: If you send me a summary of what you think are the important takeaways from any reading/lab combination, I will comment on your summary.
We'll talk for a little bit about lambdas. (This will reprise some things we talked about at the Thursday review session.)

GHS Homecoming Parade Thursday at 5:30 pm. (Small town Iowa homecoming is a fascinating experience.)
Friends of Drake Library Book Sale, Friday night and Saturday. At about 11 am on Saturday, you can get a box of books for a buck.
(Earlier, it's 50 cents for paperbacks and $1 for hardcovers.)

Campus Town Hall Tuesday at noon or 7:30 p.m.
CS extras next Thursday: Alumni
CS table Friday: Serendipity and Computing (with Grinnell's Artist in Residence)
Grinnell Prize events the following week (particularly events related to the prize winners whose project involves Web tools)

Participate in #GrinWell. http://www.grinnell.edu/forms/sign-grinwell-presidents-wellness-challenge
Friends of Drake Library needs help setting up for their annual booksale on Thursday, October 2 (conveniently, the same night as Grinnell High School's homecoming parade). You can help a good cause and probably get a few free books, too.
- Update: They can also use help on Wednesday, October 1.

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.

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.