Project: A Procedure is Worth a Thousand Pictures

Part One (Proposal) Due: 11:30 p.m., Tuesday, 13 November 2012

Part Two (Implementation) Due: 10:30 p.m., Tuesday, 20 November 2012

Summary: At this point in your career, you've learned a number of techniques for making images algorithmically. This project is an opportunity for you to explore some techniques in greater depth.

Purposes: To explore some aspect of image generation in depth. To emphasize the more creative components of this course. To encourage more purposeful image creation and reflection on algorithms.

Collaboration: We encourage you to work in groups of size three. You may, however, work alone or work in a group of size two. You may discuss this assignment with anyone, provided you credit such discussions when you submit the assignment.

Submitting: Email your submissions to . The title of your email should have the form Project and should contain your response to the appropriate part of the assignment. Scheme code should be in the body of the message. For part two, you will also submit two sets of three images and your statements following the instructions at the bottom of this assignment.

Warning: So that this assignment is a learning experience for everyone, we will almost certainly spend class time publicly critiquing your work.


It is highly recommended that you read and understand all parts of the assignment document before you begin your work on the project.

While the primary focus of this course is on learning how to write, describe, text, and analyze algorithms, our secondary focus is on writing algorithms that generate “interesting” images. We have certainly explored a wide variety of techniques for generating images. For example, you can

  • write instructions to create images using the GIMP painting tools;
  • write instructions for turtle graphics;
  • describe images as sequences of simple geometric primitives (i.e., drawings), which you can also generate algorithmically;
  • select colors or brushes from lists;
  • create interesting patterns and shapes using image-compute-pixels!;
  • use numeric recursion to create geometric figures;
  • create images by recursively dividing and coloring spaces.

You also know a number of other algorithmic techniques that could support creating images, such as various numeric functions, using lists and vectors to store collections of data, and techniques for repetition. It is now time to challenge yourself to use some of these ideas together to create images of your own design.

Rather than writing code that creates a single image, however, we want to challenge you to think about algorithmic processes that can create many different images depending on the given parameters. Hence the title, “a procedure is worth a thousand pictures.


Background: Specification

You will write a procedure, (image-series n width height), that generates the nth image in a series of at least 1000 related images. (You should be sure your procedure works for at least the integers between 0 and 999, inclusive; however, you may be more successful if you support a larger range of values.) The images should be reproducible: that is, if a user gives the same n, width, and height twice, the resulting images should be the same. You should not use randomness to vary the images; instead, the differences should be based solely on the choice of n.

In creating these images, you should use at least three different techniques for generating images that we have learned this semester (see list above).

You should strive to make these “interesting” images, images that will hold the viewer's attention. As we have noted, representational images and completely symmetrical images are less likely to hold the viewer's attention. (For example, in a picture of a cat on a landscape, the viewer is likely to say “yup, that's a cat on a landscape” and move on.) You should also be intentional about choosing colors for your images.

Your process should scale appropriately. That is, a 1000x1000 image should look similar to a 100x100 image, just bigger (and perhaps slower to compute). We will certainly use your procedure to create relatively large images that we could comfortably print on a full page or use as a desktop background.

Part One: Design Proposal

To begin your project, write a proposal consisting of two major parts.

The first part, which we will call the design statement, is intended for non-programmers and should explain the intent of your series. Are you exploring color? The use of shapes? The illusion of depth or motion? The effects of unpredictability on an image? Why? Incorporate the Elements and Principles of Two Dimensional Design and ideas about Design and Color.

After your design statement, include a sketch of at least two images from the series showing what you intend your images to look like and how they are likely to differ. (We would prefer hand-drawn sketches, although you may also generate them on the computer.)

The second part, which we will call the technique statement, is intended for your peers (that is, folks who know about as much programming as you do). This statement should explain your algorithm at a high level (in English) and how it will create the images you described and sketched in the first part. Be sure to explicitly list the three (or more) algorithmic image-generating techniques from class that you plan to use. Also explain clearly and convincingly how you will ensure that your algorithm creates at least 1000 distinct images.

Your statements should display the hallmarks of quality writing. Given that the paragraph is the "unit of composition" (according to Strunk and White), and each of these statements asks you to address several important considerations, it is likely that each statement will consist of several coherent, unified paragraphs.

We will do our best to respond to your proposal in a timely manner.

Part Two: Procedure and Images

After finishing your proposal, you should set to work on implementing your design, making sure to meet all of the specifications outlined above.

Once you complete your procedure, update and revise your design and technique statements to reflect how your project actually turned out. If there are points of divergence, you should explain why you changed your approach.

In addition, be certain your final, revised technique statement mentions the three (or more) algorithmic image-generating techniques you are using. It should also explain--via careful, precise reasoning--how you know that your procedure creates at least 1000 distinct images.

Finally, tell us three values of n that, when given as parameters to your procedure, cause it to produce especially interesting (and distinct) images.

Submitting the Project

Part One

Copy your proposal into the body of an email message and send to ; turn in your sketches at the beginning of class the next day (Wednesday).

Part Two

Email your program, updated statements, and representative values of n to .

Because it might take a while to create images, you should also provide us with copies of certain images. We would like two sets of images: one giving the three images you've chosen as particularly nice representatives of your series, and the other showing how well your procedure scales the images to different sizes. Here's how.

  1. From the Desktop, open your home directory. Create a new folder inside that is named after your project group members, e.g., username1-username2.
  2. Save or copy a .scm file containing your Scheme code into this directory.
  3. Create your three favorite images at a large size (at least 500x500).
  4. Pick a single n and create images of size 50x50, 100x100, and 200x200 with that n.
  5. Save each image into the new folder, using PNG file format and with a filename of the form username1-username2.nnn.size.png, where username1, etc., are the usernames of the team members, nnn is the number used to generate the image, and size is the size of the image (e.g., 50x50, 100x100, 200x200, or 500x500).
  6. Save your revised statements as a text file in this new directory, using the name username1-username2.statements.txt.
  7. Again, from the desktop, open your home directory. Open your new folder and verify that it contains the images, design statement, and Scheme code. Then close it.
  8. From your home directory, right click on your new folder and choose Compress.... Without changing any of the settings in the dialog, click the Create button.
  9. If you do not see the Compress... menu item, then you may do this instead. Open a new terminal, and type "tar cvfz username1-username2.tar.gz username1-username2" (using the name of your project directory rather than username1-username2). Press Enter to execute the command and create the archive.
  10. Attach the .tar.gz file you just created to the email where you turn in your assignment.


Can we reuse code from the assignments?
You may certainly reuse code from the assignments, provided you cite that code. However, you should make sure that your project goes beyond what you did for the assignment. Hence, you will likely want to extend or otherwise rewrite that code.
Can we make representational images?
We would prefer that you not make representational images. In our experience, the representational projects are often less interesting. (A thousand cartoonish houses is, well, not all that exciting.)
While we have envisioned a lot in our proposal, we are worried that we will not be able to implement everything we envision. Will we be penalized if we do less than we originally planned?
We would prefer that you aim high in the original proposals and then simplify as necessary. You will be graded primarily on your final results. Note, however, that the quality of your initial proposal will also factor in to your final grade.
Does our procedure have to work equally well for different aspect ratios?
We would prefer that your procedure handle different aspect ratios. However, if you find it appropriate to focus on a particular aspect ratio, that is acceptable. Just make sure that your statements explain why.
There is some fine detail in our image that gets lost at smaller image sizes, making smaller images look identical. Is that okay?
Your images need not be distinguishable at smaller sizes.
Some aspects of my drawing, such as the brush sizes, don't scale. Is that okay?
Yes, that is fine. We only expect you to scale the things that are reasonably scalable (such as the positions and lengths of shapes in your image).

Important Evaluation Criteria

In class, we will have two discussions: One about the aesthetics of your work and your success in meeting the criteria you have stated for yourself, and another about the techniques you use to create your images.

Your grade will be based on your statements, your code, and your success in combining multiple techniques. We will use this rubric to assess your project.

Jerod Weinman

Copyright 2007-2012 Janet Davis, Matthew Kluber, Samuel A. Rebelsky, and Jerod Weinman. (Selected materials copyright by John David Stone and Henry Walker and used by permission.)

This material is based upon work partially supported by the National Science Foundation under Grant No. CCLI-0633090. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 2.5 License .