Held: Friday, 14 February 2014

Back to Outline 15 - Homogeneous Lists: Making and Manipulating Groups of Drawings . On to Outline 17 - Exam 1 Discussion.

Summary

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

Related Pages

• EBoard (Source) (HTML) (PDF)

Overview

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

Administrivia

• A number of issues have put me significant behind. I hope to be less behind by Monday. (You will get your exams back on Monday, as scheduled.)
• No readings for Monday! We will just go over the exam.
• No Lab writeup!
• Extra credit:
  • ???

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.