Creative Coding

Develop applications and games using programming and scripting languages such as Java, C++, C#, Swift and JavaScript for platforms including Processing, Node.js, OpenCV and Unity.

Useful learning resources



  • HTML & CSS Book - A book aimed at designers introducing concepts within web development




  • Learning Processing by Daniel Shiffman
  • Nature of Codeby Daniel Shiffman




  • Daniel Shiffman has a vast collection of videos introducing programming using p5.js. Take a look through these videos if you are interested in getting a head start:

  • Kadenze is an online platform for creative education. You can take structured courses with plenty of video based content and exercises. Here is an Introduction to Programming for the Visual Arts with P5:

Programming Design Systems / Printing Code

  • A course that intersects graphic design and programming run by Rune Madesen at ITP in New York:
  • [Video] Printing Code: Programming and the Visual Arts, Rune Madsen
  • Soon to be an online book with tutorials:



Open CV





  • Face detection
  • Which Face
  • Edge detection
  • Pattern matching
  • Background Subtraction

Data Vis




"Hello, World!" in Node.js


The first program most people write when learning a new programming language is one form or another of the infamous "Hello, World!".


What you'll need to know

To follow this tutorial you should be familiar with the basics of the command-line (also known as Terminal on OS X or Command Prompt on Windows). Below are some resources that will help you get up to speed on this topic:

  • Code Academy short course - Code Academy provide a short course on command line. It has an interactive prompt in the browser so you can get to grips with the syntax before diving into the CLI.

  • An introduction to Unix and Shell - The Interactive Telecommunications Program at NYU has a very interesting introduction to Unix, which is the precursor and model for Android, Apple iOS, Raspbian (Raspberry Pi), Linux and OSx operating systems. It is also a good overview of the history, philosophy and the anatomy of the shell.

Install NodeJS

You will need to download and install NodeJS. Download the installer for your particular operating system (OSX, Windows or Linux) from the NodeJS website and follow the instructions.

To test if NodeJS has been installed successfully:

  1. Open a command line prompt (Terminal or Command Prompt)
  2. And type the following: $ node -v

Do not type the `$`. This just tells you that everything following the dollar is a single line in the command line prompt.

You should see the version of NodeJS that you installed. Something like: v4.4.7. If you see an error then you may need to downloading and installing again.

Install other software (optional)

We recommend installing and using Atom text editor, because it is free, cross-platform and good for beginners to advanced programmers.

You will be editing JavaScript files throughout this tutorial, which can be done with almost *any* simple text editor you happen to have on your computer. This excludes Microsoft's Word, Apple's Pages or other word processing software, which don't count as simple and will add other unseen characters to your file.


To create and execute our first NodeJS application we simply (1) create a text file with the .js suffix, (2) edit the file and add some JavaScript and (3) pass this file to NodeJS using the command-line prompt.

(1) Create a directory and file

Our goal is to create a directory called hello-world and within it a file called hello.js. You can create a directory and a file using many methods but below are the instructions and an animation of how this is done using the command line.

$ cd Desktop
$ mkdir hello-world
$ cd hello-world
$ touch hello.js

The commands above explained:

  • cd [directory-name] - Change the current directory you are in
  • mkdir [directory-name] - Make a new directory in your current location
  • touch [file-name] - Create an empty file


The result of this should be a directory and file on your desktop in this structure:

   └── hello-world/
      └── hello.js

(2) Edit file and add JavaScript

  • Open the file hello.js in your preferred text editor
  • Add the following code to the top of the file and save:
console.log("Hello, world of NodeJS!");

(3) Execute our hello.js script using NodeJS

  • Open a command-line prompt
  • Change directory so that you are inside Desktop/hello-world/
$ cd ~/Desktop/hello-world

TIP: When changing directory with the `cd` command (or using any command for that matter) you can use the tilde (`~`) to navigate to your home directory. e.g. `cd ~/Desktop`

- Pass your `hello.js` script to the `node` command ``` $ node hello.js ``` You should see the "Hello, world of NodeJS!" message printed out into your CLI prompt.

Below is an animation of this step.

Execute node script


Command Line Tools & Utilities

A Command Line Interface is a way of interacting with a computer by issuing commands in the form of lines of text. These commands interface with your operating system and hardware to perform complex and intensive operations.

There is a large amount of useful Free and Open Source Software (FOSS) available online that does not need or use a Graphical User Interface (GUI). Often this software works more efficiently with the operating system or directly with the hardware and therefore can perform tasks such as image, video or sound manipulation with ease.

Also because the CLI has a scripting language you can write scripts that automates certain tasks. For example:

  1. Downloading/uploading files from servers or web pages
  2. Converting, cropping, trimming, splitting, combining video files
  3. Converting, cropping, combining image files
  4. Adding effects to, combining, trimming, splitting audio files
  5. Mixing video & audio
  6. Extracting video & audio
  7. Adding text to video or images

Installing CLI Tools

Homebrew - Package Manager for macOS

Homebrew is a package manager for the macOS CLI. Once you install it on the CLI you can with one line install a lot of software from it's repository.

  1. Open Terminal

  2. Copy and paste the following line:

/usr/bin/ruby -e "$(curl -fsSL"
  1. Hit enter and it will install it for you.
  2. To test if it was successful enter the following command:
brew -v


FFMPEG is a powerful and flexible tool for performing any transformation tasks on video files.


brew install ffmpeg \
    --with-tools \
    --with-fdk-aac \
    --with-freetype \
    --with-fontconfig \
    --with-libass \
    --with-libvorbis \
    --with-libvpx \
    --with-opus \

Example use / Tutorial


The homepage for SoX calls it "the Swiss Army knife of sound processing programs" and gives the following description:

SoX is a cross-platform (Windows, Linux, MacOS X, etc.) command line utility that can convert various formats of computer audio files in to other formats. It can also apply various effects to these sound files, and, as an added bonus, SoX can play and record audio files on most platforms.


brew install sox

Example use / Tutorials


ImageMagick is a powerful image manipulation tool.


brew install imagemagick

Example use


3D Geometry and Parametric Design

This is an informal workshop experimenting with a method of generating 3D meshes from 2D images based on the RGB colour space and making this content viewable in low-fi VR headsets.

I have been making a piece of software using openFrameworks to explore creating generative 3D meshes and also the challenge of quickly and easily getting 3D models into a lo-fi VR environment. During the workshop I will introduce you to the some basic concepts of 3D modelling and explain how this software can be used as a tool to explain generative design. Below is a screenshot of the software:

Screenshot-2017-06-15-09.29.44.pngCode available here.


  • Achieve a basic understanding of concepts in 3D geometry
  • Become familiar with the concept of parametric design
  • Generate 3D meshes from found and created 2D images
  • Import 3D meshes into SketchFab, an online platform for sharing and discovering 3D models.


  • Download Google Cardboard app for iPhone or Android
  • Access to a computer

Concepts in 3D geometry

We will examine some of the fundamental principles of 3D geometry that allow the computational representation of three dimensional shapes and allow us to understand how these can be created programatically.

Public Domain 3D Cow

Glossary of Terms

  • Vertex (singular) or Vertices (plural)
    One or more points in 3D space.

  • Cartesian Coordinates
    A vertex is commonly located in 3D space using the Cartesian coordinate system. When positioning a point on you use the the X, Y and Z coordinates as show below:

3D Cartesian Coordinate

  • Primitives
    When joined together vertices make the basic building blocks of a 3D structure. The shapes formed are called primitives. Primitives can be points and lines but they become more useful when they form more complex shapes such as triangles or rectangles that can form a surface area. also known as a face.

  • Face
    As you can see from the the cow model each of the individual triangles is covered by a flat surface. Each one of these is a face, which combined make up the surface of the solid object.

  • Triangles
    To create a face you must have 3 or more vertices. This is why the triangle is the commonly used shape in 3D modelling. It is the most simple (or primitive) shape and can be used to represent the surface of a model.

  • Tesselation
    Tesselation is the process of filing a flat surface with shapes (or tiles) so that there are no gaps in that surface.

1-uniform_n11.svg.png 1-uniform_n5.svg.png 1-uniform_n1.svg.png
tessellation_texture_by_quipitory-d38nksj.png 5728579339_97f7895e02_b.jpg

Graphics cards on computers work only work with triangles so any 3D shape you see on screen will have been converted in triangles at some point by the software or by the graphics card itself.


Read more about tessellation

Parametric Design

The ground of parametric design is the generation of geometry from the definition of a family of initial parameters and the design of the formal relations they keep with each other.

What is a parameter?

In maths it is the part of an equation that can be variable, creating change in the output/result. It follows this simple model:


In programming and computation writing an algorithm follows this pattern. When an input parameter is changed the rules of the equation or algorithm produce a variety of possible outcomes. If there are multiple input parameters then those possible outcomes increase exponentially.

Algorithms as a design partner

The project below is a study of algorithms on baroque and renaissance paintings. The artist, David Quayola, leaves behind the iconographic meaning of the pictures and uses the raw information (for example colour, shape and the relationships within these) to create new pieces. The informational nature of the pictures can be used in combination with algorithms to modify outputs. No doubt within the creative process there are ways to manually delve into the code to tweak parameters and therefore manipulate the possible outcomes.

Quayola - Iconographies source Quayola - Iconographies outcome

Parametric design is also used within architecture to functionally and creatively explore the possibilities in 3D spatial design. Combining formal rules (i.e. algorithms or equations) and making small variations to the input can produce huge and sometimes unexpected shifts in outcome.


As you can see from this Google search for parametric design (June, 2017) there is a recognisable style that is reminiscent of organic shapes and patterns. Without speculating on the functional or aesthetic value of this trajectory it is without doubt a function of designing with the aid of powerful computers that can model physical systems in nature that has enabled this. The relationship between parametric design and this type of outcome is that each of these designs would be partially determined by systems of rules in computation and part by the agency of designers, architects or artists. Google Image Search - Parametric Design

Characteristics of Parametric Design

  1. Creating Composition Systems
    As a designer you often construct systems or 'grammars' that help to guide an outcome. This is the principle of parametric design however formalised into code and software.
  2. Variation
    Variation to a single parameter of a system (i.e. equation or algorithm) can create change in the output that is proportionally larger to the scale of the input. Increasing the number of parameters can again increase the variations of output exponentially! The challenge then becomes how to capture these outputs and make choices between them.
  3. Complexity
    Simple rules create complex outcomes. Also incorporating randomness into systems can increase the the variation of outcomes.
  4. Modelling physical systems
    The speed of calculations in modern computers means that simulation or modelling of physical systems is entirely possible and in doing so can become part of system of parametric design.

The Software

  1. Download software
  2. Download images

How does the software work? Let's use it and find out.


RGB Cube

If you want to recreate or learn from this yourself the code is available here and I would recommend following this tutorial for a grounding in 3D meshes in openFrameworks.

Further Reading / Watching:


How to install Node.js on Raspberry Pi

Installing Node.js on Raspberry Pi is very simple for those with basic command line experience.

In the terminal or via SSH:

  1. Add the package source: curl -sL | sudo -E bash -
  2. Install Node using: sudo apt-get install -y nodejs
  3. Confirm package is installed: node -v

Extra steps

You may also wish to install the development tools to build native addons: sudo apt-get install gcc g++ make

And you may wish to install Yarn package manager to replace NPM:

curl -sL | sudo apt-key add -
echo "deb stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
sudo apt-get update && sudo apt-get install yarn

How to make the Raspberry Pi display a web page fullscreen at power on

This short tutorial should be enough for you to be able to setup a Raspberry Pi with GUI mode and auto login enabled to disable a web page full screen automatically when it turns on.

  1. Copy into the home folder of the pi user, and run the following command: /home/pi/

sudo chmod +x

export DISPLAY=:0.0
xset s off
xset -dpms
xset s noblank
chromium-browser --noerrdialogs --kiosk --incognito
  1. Create a folder called autorun inside the .config folder of the home folder of the pi user: /home/pi/.config/autorun/kiosk.desktop

cd /home/pi/.config mkdir autorun


[Desktop Entry]
  1. Reboot the Raspberry Pi.

sudo reboot now

Workshop: Introduction to Creative Coding

Workshop: Introduction to Creative Coding

Systems in art & design

Paul Rand

Paul-Rand.jpg Eye-Bee-M-Poster.jpg

Another kind of definition is that design is a system of relationships between all of the aspects of the problem, which means the relationship between you and the piece of canvas, you and the eraser, you and the pen. The relationship between the elements proportions, which mean the relationship of sizes. I can go on all day. Paul Rand


Obj.Id_74621_web_hoch.jpg Bauhaus-Anni+Albers,+Tapestry,+1926-1964.jpg
Joseph Albers
Joseph Albers

Swiss Style

Swiss 1 Swiss 2

Linear Perspective

15th century experiments in Linear Perspective.

linear-perspective-header_0328p_duomo6_b.jpg Entrega_de_las_llaves_a_San_Pedro_(Perugino).jpg vase-in-perspective.jpg

Sol Lewitt - Instructions for making art

In conceptual art the idea or concept is the most important aspect of the work. When an artist uses a conceptual form of art, it means that all of the planning and decisions are made beforehand and the execution is a perfunctory affair. The idea becomes a machine that makes the art. Sol LeWitt

Variations of Incomplete Open Cubes sol-lewitt-instructions-1972.jpg

John Cage - Music of Changes and Chance

Music-of-changes-4-1.gif 34e9e9a994e5cda59d9940d6d0ce0d6c.png

Kerry Strand - California Computer Products Inc

nt6-cd7b343bfb9b34d15d9352474098e622_large.jpg stand01.jpg

John Albers - The Responsive Eye (1965) & Michael Noll

re2-c916bff9ad2a52de3c87bba89eee02eb_large.jpg Noll_Fig72.jpg

an intellectual and active creative partner that, when fully exploited, could be used to produce wholly new forms and possible new aesthetic experiences

Cybernetic Serendipity - Institute of Contemporary Art (1968)

Gordon Pasque - Colloquy of Mobiles
  1. Catalogue
  2. Critique

Exemplary for the appeal of the great promises made early in the computer age, Cybernetic Serendipity epitomizes the dilemma much of media art faces today: its complicated relationship with the socio-economic environment, the difficulty of engaging with its own historicity and transcending mere techno-fetishism, and the all-too-familiar sense of a naïve, unbridled optimism with its inevitable pitfalls and false dawns. link

The utilization of scientific know-how, however, did not simply lead to a re-valorization of the art object and the materials that could be made of it. On the contrary, the integration of technology engendered a growing interest that went beyond a strictly object-oriented approach toward practices that focus on process, ideas and (inter-) actions. Concomitant with experiments in participation and interaction, with happenings, performances, land art and conceptual art, media art is often regarded as a conclusion of the de-materialization of the art object. link

Digital Culture by Charlie Gere

Section on Art and Cybernetics from 1950s in Europe and the US.

Project Cybersyn


The Planning Machine

Jack Burnham - System Esthetics


Art that is transactional in that they deal with underlying structures of communication and energy exchange

Workshop: Introduction to Creative Coding

Week 1 - Coordinates, shapes and colour


  • Set up development environment
  • Understand the principles of locating points on screen
  • Drawing shapes
  • Understanding additive colour and using RGB colour space
  • Use browser-based tools for debugging and logging
  • Animate shape or colour using variables

What is p5.js?

During this series of workshops you will be using a library called p5.js to learn the fundamentals of programming. The p5.js project is the most recent part of a complex history of open-source, creative coding libraries going back to the early 2000s. It is supported by the Processing Foundation, which is a not-for-profit organisation that emerged from the creative coding library Processing.

From a technical perspective, p5.js is simply a JavaScript library. A library is a collection of code put together to simplify a task or a collection of tasks. In this case p5.js provides a lot of functionality that makes it easy to draw shapes, colours and handle user interaction within a web page.

This video from Daniel Shiffman is a good introduction to p5.js and the creative coding platforms that preceded it:

Supporting code

The code for this workshop is hosted on Github, which is a web-based repository for hosting and versioning code.

Download the code and unzip it on your desktop.

The code is also available to view directly on Github's website.

A p5.js project

In this exercise you will set up a p5.js project using the Atom text editor, then examine the different files and run the code in a browser. The code to support this section is located in the following directory and is available to view on Github:



  • p5.js project structure
  • What is a sketch?
  • What do the setup() and draw() functions do?
  • Adding your project to Atom
  • Using the browser debugging tools

A p5.js project

Below is the structure of a p5.js project, which is essentially a web project made up of HTML and JavaScript files.

  ├── index.html
  ├── libraries
  │   └── p5
  │       └── p5.min.js
  └── sketch.js


p5.js is a JavaScript library designed for drawing to a web page. For JavaScript code to run in a browser it needs to be included in a HTML file. The index.html file is the 'entry point' for the browser to access our project code. Note the use of the <script> tag to import two JavaScript files (line 7 & 8).

<script src="" id="bkmrk--0"></script>

The first JavaScript file (libraries/p5/p5.min.js) is the p5.js library containing a vast amount of code that we can use without having to fully understand.

The second JavaScript file (sketch.js) is where we write our own code.


Below is the minimum required code for a p5.js sketch. This is simply an empty template for us to start coding and will not produce any visual results.

<script src="" id="bkmrk--1"></script>

To summarise, we now know that when the browser loads the index.html file, it will import the p5.js library and the sketch.js file, and then execute the code we have written.

Sketch - Why a sketch?

setup() and draw()

Within the sketch we have two functions: setup() and draw(). p5.js calls/runs these functions for us in a particular order. The setup function runs first and only once. The draw function then runs repeatedly until the web page is closed.



When coding in any language and with any level of experience or expertise, you will almost always encounter bugs. Writing code is often a trial and error process. Therefore, to be productive programmers we need debug our code in order to identify and fix problems. This means using tools to show us where errors in our code occur whilst it is being executed in its runtime environment.

p5.js is written in JavaScript and therefore the environment for running our code will be the browser. There are developer tools built into all the major browsers that van be used for debugging. For now, we recommend using Chrome so we are all using the same tools throughout the workshop. Chrome has an easy to use and fully featured set of developer tools also known as DevTools.


  • Add the 00_empty_project directory to Atom
  • Open index.html in a browser
  • Use the developer tools to see logged messages

Coordinates and Shapes

In this exercise you will learn how to locate and target positions (i.e. pixels) on screen for drawing. We will also learn how to use some basic functions of p5.js for making primitive shapes. The code to support this section is located in the following directory and is available to view on Github:



  • Comments
  • Using p5.js functions
  • Drawing some simple shapes
  • Locating points on the screen using Cartesian Coordinates
<script src="" id="bkmrk--3"></script>


When writing code it is a good idea to sometimes write notes to yourself or other coders to explain what the code is meant to be doing. The way we do this is by adding comments. Comments can be added in two ways:

  1. Single line comment
    Using the double forward slash (//) at the beginning of the line instructs the browser to ignore that entire line.
// This rectangle is the button that starts the game.
rect(20, 100, 50, 100);
  1. Block quotes
    A forward slash and an asterisk (/*) will start the comment block and the reverse, an asterisk and a forward slash (*/), will end it. The browser will ignore everything in between, which can be multiple lines of notes.
This is a reminder that the code below is not complete yet. 
It might be improved by taking this code and making it into 
a function of its own.

You will see comments used in this exercise to ignore lines of code that are incomplete or contain errors.

p5.js drawing functions

We will address functions in more detail later but here is a brief explanation. A function is multiple lines of code that achieve a specific task. These are grouped together and given a name so that they can be used again and again.

Later on we will write our own functions but, for now, we will use some functions that are provided by the p5.js library.

  • createCanvas(800, 450)
    This is called inside setup() to create a drawing area of a certain width and height – in this example the canvas is 800 pixels wide and 400 pixels high.
Within the p5.js library a [HTML canvas element]( is created.

  • rect( 50, 100, 200, 40 )
    This function draws a rectangle 50 pixels from the left of the canvas (x), 100 pixels from the top (y). The width of the rectangle will be 200 pixels and the height will be 40 pixels.

Cartesian Coordinates

To understand how to position elements on screen we need to go back to school. When drawing to a screen on the majority of programming languages will use a version of the Cartesian Coordinate system.

It was a system developed in the 17th Century by René Descartes for locating unique points on a mathematical representation of a 2D plane using numerical pairs; e.g. (50, 100), (251, 122). This revolutionised the fields of geometry and algebra centuries before the first computer screens.

For our purposes, the numerical pairs represent the number of pixels counting from left to right (x) and top to bottom (y). For most, the diagram on the left will be familiar for plotting points on a graph:

(image credit:

The only difference between plotting points on a graph and on a screen using code is that (in nearly all languages) we plot points on a screen starting from the top left corner rather than the centre. You need an x value (horizontal position) and a y value (vertical position) in order to specify a pixel position on screen.

Using coordinates in functions

In our code we call the following function:

rect( 50, 100, 200, 40 );

The function accepts 4 arguments that define the position and shape of the rectangle:

rect( x, y, width, height);

Therefore the result of this will be the following:


Each function in the library can take different arguments depending on its purpose. For example, when defining a line we do not specify the width and height because lines are 1 dimensional (they have zero or negligible height). Instead, a line is better defined by a start and end position on our screen; two sets of Cartesian Coordinates:

line(x1, y1, x2, y2);

Below is a diagram showing how this using the cartesian coordinates system.

drawing-06.png(image credit:

You will not be expected to instinctively know what arguments to give to a particular function like line() or rect(). When using libraries written by someone else, it is common for the authors to provide online documentation describing each of the functions.


We know from our sketch that the rect() function accepts a minimum of 4 arguments: x, y, width and height. Without being told, how do we know what these parameters mean? And what about other functions like triangle() or quad()?

To find out, we check the online documentation provided by the authors of the library or programming language. You can search online for the function you are using and the documentation will give you all the information you need to use it, typically with some useful examples. We can check the reference for p5.js, and specifically the page that explains the line function.


  • Add the 01_coordinates_and_shapes directory to Atom
  • Open index.html in a browser
  • Change the position, width and height of the rectangle
  • Draw a line
  • Draw an ellipse, triangle, or quad


The code to support this section is located in the following directory and is available to view on Github:


RGB Colour Space

When defining a colour in code, we need to describe it numerically using a 'colour space'. The most common colour space used in computing is RGB (Red, Green, Blue). Those with experience of graphical software such as Photoshop will be familiar with the colour selector that shows you the RGB values as your move around the colour palette:


An RGB colour can be understood by thinking of it as all possible colours in the visible spectrum that can be made from combinations of red, green, and blue light. By defining the intensity of each of the three colours that are mixed together, it's possible to pick from over 16 million different colours. Arguably more than the human eye can see.

In practical terms, we specify the individual amounts of red, green, and blue using values between 0 and 255.

For example, this describes the colour red:

255, 0, 0     <---- RED

This describes green:

0, 255, 0     <---- GREEN

And this describes the orange colour used on this website:

255, 152, 0     <---- ORANGE

Additive colour


In contrast to subtractive colour models, such as CMYK used for paints and print, the RGB colour space is additive. When you mix the primary paints or pigments together the resulting colour will become increasingly dark, working its way towards black. With colour displayed on a computer monitor or mobile device, adding red, green and blue together will provide white.

If you want to know all there is to know about colour theory then read Joseph Alber's amazing book, Interaction of Colors.

Using colour functions

In the p5.js library there are functions provided for controlling the colour of the fill and stroke of shapes.

  • fill(r, g, b)
    This determines the main body of colour inside a shape.
  • stroke(r, g, b)
    This defines the colour of the line that surrounds the shape.

Here are some examples of giving three arguments (r,g and b) to the fill and stroke functions:

  1. fill( 255, 0, 0 ) // red shape fill
  2. fill( 255, 255, 0 ) // yellow shape fill
  3. stroke( 0, 0, 255 ) // blue outline
  4. stroke( 255, 0, 255 ) // magenta outline


Another feature of these functions is the ability to use them to define grayscale values. Passing a single argument between 0 and 255 will result in a colour between black and white:

  1. fill(0) // black shape fill
  2. fill(255) // white shape fill
  3. stroke(150) // grey outline

Order is important

When calling these functions you are defining the fill and stroke colour for all the shapes you draw after that line of code. So it is important to pay attention to the order in which you use them.


The code below draws a selection of shapes around the canvas. They are all coloured white, gray or black. Your task is to add some colour to this situation.

<script src="" id="bkmrk--8"></script>
  • Add the 02_colour_stroke_fill directory to Atom
  • Open index.html in a browser
  • Change the fill and stroke colour for each shape

Simple Interaction and variables

The code to support this section is located in the following directory and is available to view on Github:


p5.js defines some variables that we can use in our code about the properties of the sketch and also user inputs (e.g. mouse and keyboard). We can use these to make our code easier to maintain, more flexible, and to possibly add some basic interactions.

What is a variable?

A variable is how we store useful values in code. The types of things we can store depends on the programming language being used, but common examples are numbers and text.

Think of a variable as a container or box. The value is the thing inside the box, and the label on the front of the box is the name we use to identify it.

var myNumber = 5;
var myText = "hello";

In reality, the variable's container is a small section of memory on your computer.

p5.js provided variables

After you've called the createCanvas(width, height) function, p5.js automatically stores the specified dimensions as variables named width and height that can be used throughout your sketch. For example, you can use those variables to calculate and draw something in the exact centre of the canvas:

rect(width/2, height/2, 20, 20);

Special variables, such as mouseX and mouseY are made available by p5.js. These are extremely useful if we want to make sketches that respond to the user's mouse input. These two variables contain the x and y coordinates of the user's mouse at that precise moment. We can use changing values to modify our drawing and create something more dynamic.

<script src="" id="bkmrk--9"></script>


  • Add the 03_simple_interaction directory to Atom
  • Open index.html in a browser
  • Change the provided code so that a shape follows the mouse around the canvas

Week 1 Assignment

For the next workshop, I would like you to make a portrait (self or other) using what you've learned from week 1. You should use the following functions and variables:

  • rect()
  • ellipse()
  • triangle()
  • fill()
  • stroke()
  • mouseX / mouseY

I would like you to use Codepen to submit your work. Codepen is an online code editor for web based technologies (HTML, CSS & JavaScript) as well as a platform for sharing your code. I have created a template for you to use that already includes the p5.js libraries:

Codepen - Create Pen from template

Workshop: Introduction to Creative Coding

Week 2 - Animation, conditionals & random numbers


  • Understand variables and how to use them
  • Understand functions and how to use them
  • Using conditional statements to control code flow
  • Using variables for animation
  • Using random numbers
  • Mapping values from one range to another

Supporting code

The code for this workshop is hosted on Github, which is a web-based repository for hosting and versioning code.

Download the code and unzip it on your desktop.

The code is also available to view directly on Github's website.

During this workshop session we will be using the following project directories:



Firstly let's take another look at variables in a bit more detail. A variable is simply a way of storing information in the computer's memory. Let's dive right in with an example...

var rectWidth = 5;

Let's break down the above statement:

  1. var - This is how the browser knows you are 'declaring' a new variable
  2. rectWidth - This is the name of the variable, which we can refer to later in our code. What you call a variable is up to you but there are some conventions.
  3. 5 - The value which we want to store in the computer's memory

Read more about variables in JavaScript

Using variables

Supporting Code
The code to support this section is located in the following directory and is available to view on Github:

Now that our variable rectWidth is stored in memory, we can access it using its name to return the stored value.

var rectWidth = 5;
var rectHeight = 7;
var rectArea = rectWidth * rectHeight; 
console.log(rectArea); // This will write 35 to the console.

In this example, a new variable rectHeight is declared and assigned a value of 7. On the third line both the previous variable values are retrieved from memory and multiplied using the multiply operator (*). This is immediately stored in the rectArea variable before finally being logged to the console.

Here is what happens line by line:

  1. Store the number 5 in a variable named rectWidth
  2. Store the number 7 in a variable named rectHeight
  3. Multiply the values in rectWidth and rectHeight, storing the result in a variable named rectArea
  4. Log the value of rectArea


  • Add the 04_using_variables directory to Atom
  • Open index.html in a browser
  • Open and look at the console in the browser's developer tools
  • Remove the comments at the beginning of line 20 and reload your browser

Animation using variables

The code to support this section is located in the following directory and is available to view on Github:


In this exercise a variable will is used to store, retrieve and increase a value. This value will represent the position of a shape drawn to the canvas.

Here is a portion of the code extracted from the provided example:

var positionX = 0;

[code excluded]

function draw(){
  // Set the background to black every frame

  // Draw a rectangle that moves along the X axis
  rect(positionX, height/2, 10, 10);

  // Increase the value stored in positionX
  positionX = positionX + 1;

As you can see a variable called positionX is declared and assigned a value of 0. Importantly this variable is declared outside of the function where it is later used. The variable is declared in the global scope (more on this later) making it accessible throughout the entire application (i.e. globally).


  • Add the 05_animation directory to Atom
  • Open index.html in a browser
  • Use the conditional if statement to reset the square to position 0.
  • Increase the speed of the rectangle
  • Move the rectangle on the X and Y axis


The code to support this section is located in the following directory and is available to view on Github:


A conditional statement is used to control which code is executed based on certain pre-determined conditions. This process is one method of controlling the flow of our application.

If statements

Conditional statements are written in code using the if keyword. In fact, conditional statements are often referred to as if statements. Below is an example of how a conditional statement is formed using the if keyword:

if (condition) {
  // code that runs if the condition is true

By replacing the condition above with other statements we can start to control what parts of our code are executed under which conditions.

You can think of this as a very simple flow diagram or decision tree. If condition A is TRUE then the code block runs, however if it's FALSE the code is ignored.

Is the statement true or false?

When writing a condition, commonly known as a conditional statement, the truth of the statement is being evaluated or checked. In the following examples this happens by comparing two values. These values can be variables, literal values or a combination of the two.

Literal values
Literal values are those that we write in our code literally.As opposed to variables that can change, these values are written explicitly in our code and do not change. Here are some examples:
"Hello, World"

Here are some practical examples of if statements that use both variables and literal values. Between each set of brackets is a statement comparing two values. Those comparisons will return a value of true or false, which determines if the code within should be executed or ignored.

if( userName == "bob" ){
   // Any code in here will run when userName is equal to ('==') "bob"

if( durationHours > 12 ){
  // Any code in here will run when durationHours is greater than (`>`) 12

if( rectArea <= 35 ){
  // Any code in here will run when rectArea is less than OR equal to ('<=') 35

Comparison operators

In conditional statements, a comparison operator sits between the two values and is used to determine whether the statement is true or false. Below is a list of conditional statements using different comparison operators.

A == B A equal to B
A != B A is not equal to B
A > B A is greater than B
A < B A is less than B
A >= B A is greater than or equal to B
A <= B A is less than or equal to B

If the statement is true then the code within the conditional will run. Here are some more practical examples:

value1 == value2
userName == "bob" 
playerScore >= 10 
"west" == windDirection
juneTemperature > mayTemperature

Let's break down one of the above conditions:

  1. userName
    A variable – as the word 'variable' suggests, we expect it may change.
  2. ==
    A comparison operator checking for equality – checks if the value on the left is equal to the value on the right.
  3. "bob"
    A string literal – written explicitly and therefore will not change.

Since variables can change value throughout the execution of code, the comparison to a static value causes code to run only during particular conditions.

If variables are named well you can start to read through the logical steps of your application by reading the code as human language:

if the userName is equal to "bob"
  then do something
Double (==) and single (=) equals signs
Always be sure to use the double equals sign in conditional if statements. Using the single equals sign will change the value stored inside the variable.


  • Add the 06_conditionals directory to Atom
  • Open index.html in a browser
  • Modify the code inside the first conditional to make the ball bounce off the right side of the canvas
  • Use another conditional to make the ball bounce off both sides of the canvas
  • Change the colour, size, speed of the ball when it bounces off the wall
  • Move up and down instead of left and right

Using random numbers

The code to support this section is located in the following directory and is available to view on Github:


Most programming languages provide functions for generating random numbers. This can be very useful in providing some variations to deterministic behaviour of code.

In p5.js there is a function for generating a random number between a minimum and maximum value:

random(min, max);

The min and max arguments set the minimum and maximum values that can be returned from that function.

random(0, 10);
random(120, 180)
random(15, 22);

You can also use a variable as one of the arguments:

random(0, width);
random(0, height);

The random() function can be used to set properties of shapes in our sketch such as position, size or colour.

In the following example the positionX and positionY variables are assigned values that are half of the width and half of the height of the canvas respectively. This will place the ellipse in the centre of the canvas when the code runs.

var positionX;
var positionY;

function setup() {
  createCanvas(800, 450);
  // Assign a value to the variables
  positionX = width/2;
  positionY = height/2;

function draw() {
  // Use the value within the variables.
  ellipse(positionX, positionY, 10, 10);

Here is an example of how to use the random function to change the starting position of the ellipse to a random position on the canvas on every execution of the code.

var positionX;
var positionY;

function setup() {
  createCanvas(800, 450);
  // Assign a value to the variables
  positionX = random(0, width); // Random number between 0 & 800
  positionY = random(0, height); // Random number between 0 & 450

function draw() {
  // Use the value within the variables.
  ellipse(positionX, positionY, 10, 10);
The Nature of Code
For an in-depth look at how random numbers relate to other programming concepts such as probability, evolutionary programming and the 1982 sci-fi classic Tron, take a look at Daniel Shiffman's free online book The Nature of Code.


  • Add the 07_random directory to Atom
  • Open index.html in a browser
  • Change the X and Y positions of the ellipse using random() on every frame
  • Change another feature of the shape with random (size, colour, etc)

Randomness and probability

The code to support this section is located in the following directory and is available to view on Github:

  • Add the 08_random_recursive_tree directory to Atom
  • Open index.html in a browser and you will see something similar to this:

This is an example of using randomness and probability to produce organic forms. Take a look through the code and you will see some lines such as this:

// Create a random numbers between 0 and 1
var r = random(0, 1.0);

// 98% chance this will happen
if (r > 0.02) {
  [code excluded here]  
// 2% chance this will happen
else {
  [code excluded here]

You can see that by using random numbers and conditional statements you can quite easily create systems that have interesting and unexpected results within the limits of probability.

This code also uses a very powerful technique called recursion, which is beyond the scope of this workshop. Essentially the code is self-referential and therefore within very few lines of code can create complex outputs.

Mapping values

The code to support this section is located in the following directory and is available to view on Github:


A common programming task – particularly when visualising information – is to take a value that is changing within one range and mapping that onto a different range.

As an example, let's think about visualising the current temperature (a changing value) by drawing a thermostat.

We know that the value is going to be in this approximate range of 0 to 50 °C and the size of the red thermostat indicator is a shape with a height between 0 and 200 pixels:

°C 0 50
pixels 0 200

Let's assume we have retrieved the current temperature in degrees centigrade, for example through a weather API.

If the temperature is 50°C, the height of the red bar would be 200 pixels; if the temperature is 0°C, the height would be 0 pixels; and if the temperature is 25°C (half way point of the range), the height would be 100 pixels (half the height).

Current Temp (°C) Height (pixels)
0 0
50 200
25 100
10 40
35 140

Using the map function

Within p5.js there the map function performs the calculations that translates one range onto another. The map() function takes 5 arguments:

map(value, fromMin, fromMax, toMin, toMax); 

So using the example of the thermostat, we would convert the current temperature stored in a variable called temperature using the following:

map(temperature, 0, 50, 0, 200);

And here are some examples from above using literal integer values:

map( 25, 0, 50, 0, 200 ) // returns 100
map( 10, 0, 50, 0, 200 ) // returns 40
map( 35, 0, 50, 0, 200 ) // returns 140


  • Add the 09_map_weather_api directory to Atom
  • Open index.html in a browser
  • Look through the code and find where the map() function is used
  • Change the city in the preload function to see the API results from other places

HSB Colour

The code to support this section is located in the following directory and is available to view on Github:


Using the RGB colour space we can produce as the specific colours we need. However, in order to manipulate or generate colours, the RGB colour space doesn't offer the best tools. For this we can use the HSB colour space or Hue, Saturation and Brightness. It is sometimes also known as as HSL (lightness) or HSV (value).

Within this model the hue defines the colour we see, which is the wavelength of light being produced. The saturation defines how intense or vivid the colour is. The way the colour is desaturated is by the addition of grey: 100% saturation means there is no grey and 0% saturation will result in a medium grey. The brightness determines the amount of black or white that's mixed with the hue.

Here are the RGB and HSB colour spaces visualised:


Changing colour mode

In p5.js you can change the colour space from RGB to HSB using the following.


The colorMode function can also take 3 more arguments:

colorMode(HSB, 360, 100, 100);

These last 3 arguments represent the range of values we can pass as arguments into the colour functions such as fill() and stroke().

In RGB colour mode, the range is by default:

Red Green Blue
0 - 255 0 - 255 0 - 255

But in HSB mode, the hue is usually between 0 and 360 whilst the saturation and brightness are between 0 and 100.

Hue Saturation Brightness
0 - 360 0 - 100 0 - 100

The saturation and brightness are essentially represented as a percentage (0 to 100%) of their most extreme condition, which is the least saturated and the most bright.

But why is the hue value between 0 and 360? As mentioned the HSB colour is visualised as a cylinder (or sometimes as a cone) and the hue is represented as the perimeter of the circle that sits at the top of the 3D shape. Therefore the 360 is the angle in degrees around that circle.

Image credit:


Using the HSB colour space we can create easily create colour schemes that have a mathematical relationship to each other. A simple example is choosing a particular hue and saturation and then adjusting the brightness. However you can also choose selections of hue based on their relationship around the 360 degrees of the colour wheel.


All of these examples are from the Rune Madesen's lecture on colour as part of his Printing Code module at ITP. The online resources from this are extremely useful.

In the provided example, the mouseX value is being mapped from one range (0 to width) onto another (0 to 360):

width of canvas 0 50
degrees of colour wheel 0 360

Therefore as the mouse moves across the canvas the mapped value travels between 0 and 360. This is then used to set the hue of the fill colour showing the full spectrum of colour.

var colour = map(mouseX, 0, width, 0, 360);
var columnWidth = width/3;

fill(colour, 100, 100);
rect(columnWidth*0, 0, columnWidth, height);

fill(colour, 80, 70);
rect(columnWidth*1, 0, columnWidth, height);

fill(colour, 60, 40);
rect(columnWidth*2, 0, columnWidth, height);

  • Add the 10_map_hsb_colours directory to Atom
  • Open index.html in a browser
  • Explore different values for brightness and saturation
  • Create colour schemes with hues that have are related on the colour wheel, e.g. analogous, triadic, etc.


Functions are used to define a process that can be constructed of one or more lines of code. They are often used to organise and structure code by the intended outcome or behaviour.

Here are a few benefits to using functions:

  1. Keep code organised
  2. Make code easily reusable
  3. Breaking down a task into smaller pieces (decomposition)
  4. Making problems in the code easier to identify and troubleshoot (seperation of concerns)

Using functions

Making use of functions is broken down into two parts. First, the function behaviour needs to be defined, i.e. the code needs to be written. Secondly, the function needs to be called (also known as 'executed').

Define the function behaviour

Below are 4 lines of code contained within a function that perform the task of calculating the area of a shape. This is where the function is being defined.

function calculateArea() {
  var width = 5;
  var height = 7;
  var area = width * height;

Let's break down the unfamiliar parts of the above code:

  1. function
    This is how the browser knows you are declaring a new function.
  2. calculateArea()
    'calculateArea' is the name of the function, which we can use to refer to later in our code. What you call a function is up to you but there are some conventions.
  3. { }
    These are curly brackets or curly braces. They start and end the content of the function. All code written between these two brackets is the behaviour of the function.

Call the function

The above code will do nothing until we call the function elsewhere in our code.

calculateArea(); // Logs 35

Function parameters

A common use of a function is to make our code more reusable. One way of making our functions more reusable is by adding parameters.

function calculateArea( width, height ) {
  var area = width * height;


Part 1

Create a sketch that includes:

  • one or more elements that changes over time.
  • one or more elements that is controlled by mouse or keyboard
  • one or more element that is random() in nature

Work can again be submitted using Codepen. Here is the URL for the p5.js template:

Please submit the Codepen URL the day before our next workshop.

And here is a short guide on using Codepen:

Codepen - Create Pen from template

Part 2

When you submit your URL I would like you to also submit a question about what we've been covering (or have missed) over the last two weeks. For example:

  • What does a certain error message mean?
  • How do I create a colour with an alpha channel?
  • Are there any other colorModes?
  • What is the highest framerate?
Workshop: Introduction to Creative Coding

Week 3 - Iteration, arrays, objects and pixel arrays


  • Iteration using while and for loops
  • Understand and using arrays
  • Using loops and arrays together
  • Understanding and using JavaScript objects
  • Understanding how colour data is stored in pixel arrays
  • Accessing the webcam

Supporting code

The code for this workshop is hosted on Github, which is a web-based repository for hosting and versioning code.

Download the code and unzip it on your desktop.

The code is also available to view directly on Github's website.

During this workshop session we will be using the following project directories:


Local web server

So far during this series of workshops testing your code has involved opening the index.html file in your browser, which results in an absolute file path in the browser address bar (see below). You can see this indicated by the file:// protocol followed by the absolute file path to the index.html file:

For some examples you will need to run a local HTTP web server that serves the files in a project. If you have Node.js already installed you can run the following command to install an HTTP web server:

sudo npm install -g http-server

If you receive an error from the above command it's likely that you do not have Node.js installed. In which case visit the Node.js homepage and download/install the LTS version and repeat the command above.

Once you have installed the HTTP web server you will need to change directory (cd) into the project directory on the command line and run the server:

cd ~/Desktop/intro-to-programming-2017/15_image_pixel_array/

If successful you will see messages in the command line similar to this:

You can then copy and paste one of the URLs into you browser:

Iteration: while and for loops

Supporting Code
The code to support this section is located in the following directory and is available to view on Github:

Sometimes it is necessary to repeat a task over and over on the same data in order to achieve a desired outcome. This is known as an iterative process and each step is an iteration.

The most common application for iteration is to create, check, or modify a collection of variables.

In the previous workshop, we were introduced to the idea of conditionals. We saw that an if statement can be used to branch code, but this is only performed once.

If we want to perform a conditional operation repeatedly, we need to use a different statement – the while loop.

The example below will draw six circles onto the canvas. Note that the circles are identical, apart from the x coordinate.

function setup() {
  createCanvas(400, 300);

function draw() {
  ellipse(50, 225, 20, 20);
  ellipse(100, 225, 20, 20);
  ellipse(150, 225, 20, 20);
  ellipse(200, 225, 20, 20);
  ellipse(250, 225, 20, 20);
  ellipse(300, 225, 20, 20);
  ellipse(350, 225, 20, 20);

We can simplify this code by using a while loop.

function setup() {
  createCanvas(400, 300);

function draw() {
  var x = 50;
  while (x <= 350) {
    ellipse(x, 225, 20, 20);
    x = x + 50;

What's happening in the above example line-by-line:

  1. var x = 50;
    Here we create a temporary variable to help us iterate. In this case an integer, initially set to 50.
  2. while (x <= 350) {
    This starts the while loop. As long as the condition inside the parentheses remains true, the code that follows the curly brace will be repeatedly executed (forever!)
  3. ellipse(x, 225, 20, 20);
    We draw a circle. The y-position, height, and width are identical for each; the x-positon is set using the current value of our temporary variable.
  4. x = x + 50;
    The value of the temporary variable is increased by 50.

As soon as the condition inside the parentheses returns false, the while loop exits and code execution continues.

Although this is a very common code pattern, it's unusual to see while loops actually used in code. This is because most programming languages provide us with a more useful variant – the for loop.

A for loop is written slightly differently from a while loop. The parentheses contain three statements separated by semicolons, rather than a simple test.

function setup() {
  createCanvas(400, 300);

function draw() {
  for (var x = 50; x <= 350; x = x + 50) {
    ellipse(x, 225, 20, 20);

What's happening inside the parentheses:

  1. for (var x = 50; x <= 350; x = x + 50) {
    A temporary variable is declared and initialised in the first statement.
  2. for (var x = 50;x <= 350; x = x + 50) {
    The second statement contains the condition that is checked. If this returns false the loop exits.
  3. for (var x = 50; x <= 350;x = x + 50) {
    The final statement contains code that is to be executed after each successful loop.

Even in these basic examples, it's clear to see that loops help us avoid repetition and reduce the number of lines of code we write.


  • Add the 12_iteration_02/ directory to Atom
  • Open index.html in a browser
  • Change the RGBA values of the pixels inside the nested for loop
  • Try using the random() function to set the colour values
  • Try using the x and y variables to set the colour values

JavaScript Arrays

Arrays are essentially ordered lists of things and each item in that list can be accessed individually. The array itself is a type of variable and it stores other variables inside. The stored variables can be used in the same way as you use any other variable.

Here is a simple array:

var sizes = [ 20, 350, 80, 210 ];

What's important about an array is the order of the items within. To access any individual item of data stored inside the variable, we need to reference the item's position, commonly referred to as the array index. Crucially, the index of an array starts at zero:

console.log(sizes[0]);  // logs: 20

And therefore the index of the last item in the array would be one less than total number of items. In our example above we have 4 items, so the final item is accessed using the index 3:

console.log(sizes[3]);  // logs: 210

JavaScript arrays are particularly useful since you can store any type of data inside, including integers, strings, objects and—perhaps confusingly—other arrays. Here is an example of an array containing a list of strings:

var technicians = [ "Delia", "Will", "Adam", "Gareth", "Tom" ];

And, as above, we can access the strings using the array variable technicians and counting along the list starting from zero:

console.log( technicians[0] ); // "Delia"
console.log( technicians[2] ); // "Adam"
console.log( technicians[4] ); // "Tom"

Try this for yourself using this CodePen.

Loops and arrays

Supporting Code
The code to support this section is located in the following directory and is available to view on Github:

When we have only a few items in our arrays, it is not a lot of additional code to access each of them explicitly using their index:

ellipse(x, y, sizes[0]);
ellipse(x, y, sizes[1]);
ellipse(x, y, sizes[2]);
ellipse(x, y, sizes[3]);

But even this is repeating code unnecessarily. And when we start to hold hundreds or thousands of items in our array, it would become unmanageable to write out the code above.

To unleash the full potential of arrays, they can be combined with looping structures such as for loops. As we have seen already, the for loop can be used to run a piece of code a number of times, incrementing an index variable on each execution:

for( var i = 0; i < 4; i++ ){
  console.log( i );

A further useful feature of arrays is that they have an internal property that contains the current length of the array:

var sizes = [ 20, 350, 80, 210 ];
console.log(sizes.length);        // logs 4

The length property can be used within our for loop to determine how many times the loop runs the code before stopping. In the case of our sizes array above, the loop would continue to execute as long as the i variable is less than (<) the number of items in the array.

This is a very common design pattern.

for( var i = 0; i < sizes.length; i++ ){
  console.log( i ); 

What is happening here?

  1. The variable i is set as 0
  2. The statement i < sizes.length is tested
  3. If the condition is true the code inside runs
  4. ...and the variable i is increased by 1
  5. Go back to point 2 and repeat until false

The code would run 4 times and log 0, 1, 2 and 3.

Now we have a loop that runs as many times as there are items in the array. Crucially, inside that loop, the variable i is incremented by 1. Each time it increments by 1 we can use it to access the value in the array at that index:

for( var i = 0; i < sizes.length; i++ ){
  console.log( sizes[i] );

If we recall that the first item in an array uses the index zero, we can see why our i variable is initialised as 0 rather than 1.

Within our for loop we are now running code that accesses each of the items in the array in the correct order.

See this code executed in CodePen.

JavaScript Objects

In JavaScript most things you encounter are actually objects. The strings, arrays and even functions are objects at the most basic level. This is because they can all contain properties and functions inside them.

Here, for example, the variable message has a property called length that returns the length of the string:

var message1 = "what is an object";
console.log(message1.length); // 15

More examples on CodePen.

These are objects within internal properties and functions that are provided by the JavaScript engine inside the browser. We do not need write the code for these objects as it already exists.

However, creating your own objects is a very handy way to encapsulate related functions and variables, and also act as data containers. We can also use this technique to model things in a more helpful way.

Let take a look at the variables needed to draw a circle and then how we would move those variables inside an object. Here we define three variables:

var x = 50;
var y = 100;
var size = 20;
ellipse( x, y, size );

And here are the same three variables inside an object:

var circle = {
  x    : 50,
  y    : 100,
  size : 20

The first thing to note is that the object starts and ends with curly braces; the same way that we start and end functions and if statements.

Pay careful attention to the differences between declaring variables inside and outside of an object. Variables stored inside objects are called properties and each property has a value. The major difference in syntax is that properties and values are separated by a colon (:) instead of an equals sign (=).

x    : 50,  // Note the colon ':' separator...

And each of the property/value pairs are separated by a comma (,), not a semi-colon (;). The exception to this is rule is the last pair for which the comma is optional

x    : 50,  // ...and each pair separated by a comma
y    : 100, 
size : 20   // except the last, which is optional

So now that the data that defines our circle is contained within an object how do we access that data? To access a property of an object the dot syntax is used. For example to access the x value:


So to rewrite our code above using an object:

var circle = {
  x    : 50,
  y    : 100,
  size : 20

ellipse( circle.x, circle.y, circle.size );

See a simple example of this on CodePen.

Object Oriented Programming
A more advanced use of objects is to create templates of things that we want to represent in our code. These templates or models can be used to create different permutations of the same type. This is called abstraction and is one of the fundamentals of object-oriented programming (OOP). Mozilla Developer Network has a very good section about objects and a really interesting page introducing OOP and how to implement it using JavaScript objects.

Here is an example on CodePen of the above circle sketch created using a constructor function. This is a simple example of using Object Oriented Programming in JavaScript.

Pixel array

Supporting Code
The code to support this section is located in the following directory and is available to view on Github:

Previously we have discussed that our p5.js canvas is made up of individual pixels. Each of them can be located using an X coordinate between 0 and the width and a Y value between 0 and the height. Also known as Cartesian coordinates.

So how many pixels are there in a canvas of 600 pixels in width and 500 pixels in height:

600 x 500 = 300000 pixels

We have also discussed that each pixel is made up of three values: red, green and blue. Well, there is actually a fourth value, which we haven't discussed in a great detail called alpha. This sets the transparency value of the pixel. So for every pixel on the p5.js/HTML canvas there are 4 pieces of information:

red, green, blue, alpha

So in total for our canvas of 600 x 500 we have this many pieces of information:

300000 (pixels) x 4 (colour value) = 1200000

All of this information is stored in one large linear array, which we can easily access and manipulate. However arrays are simply lists so they do not have a concept of which index relates to which X and Y coordinate on our screen.

If we want to access a particular pixel we do not refer to it as, for example, the 29th pixel (the last pixel in our example above). We are more likely to reference it using the X and Y coordinates. So how do we get from an X and Y coordinate to access and manipulate the 4 colour values within the pixel array?

In the image above the red dot represents a pixel on screen that we want to target in the pixel array to access or change the 4 colour values.

If we were to count the grey boxes you can see that before we reach the red dot we have 2 full rows, which equates to (y * width). Then we count in (or add) x positions. The formula to calculate this for any x and y value is therefore:

x + (y * width)

So far so good. However now we know that the number of the pixel in the canvas but for every pixel there are 4 values in the array. Therefore to calculate the first of four positions in the array that contains the RGBA values for our pixel we simply multiple by 4. In our above example we have calculated the pixel position to be the 16th:

16 (pixel position) * 4 (colour values) = 64 (array index)

So now we know that the four positions in the array that represent our pixel are 64, 65, 66 and 67. We can therefore write the following code to manually set the colour of that pixel:

function draw() {

  pixels[64] = 255;    // red
  pixels[65] = 255;    // green
  pixels[66] = 255;    // blue
  pixels[67] = 255;    // alpha


But that is not very reusable code and we would have to manually calculate the index again every time we wanted to address a new pixel. What would be much better is to put all of those calculations into variables so we can simply change the X & Y value with ease:

I've increased the size of the canvas to 60 pixels in width by 50 pixels in height so we have a slightly larger area to spot our pixel in.

function draw() {

  var x = 40;
  var y = 20;
  var index = ( x + (y * width) ) * 4;

  pixels[index] = 255;      // red
  pixels[index+1] = 255;    // green
  pixels[index+2] = 255;    // blue
  pixels[index+3] = 255;    // alpha


Using the above code we can address a particular pixel and then access the colours within the pixel array.

Try changing the X and Y values on this CodePen. You may need to look closely or zoom in to see the single coloured pixel.

So we now can access individual pixels based on their X & Y coordinates, what if we wanted to modify all the pixels. We can do this by using a nested for loop to iterate along every pixel on the X and Y axis. A nested for loop is one loop within another:

// Loop through every pixel on the X axis...
for ( var x = 0; x < width; x++ ) {
  // ...and for each X, loop through every pixels on the Y axis
  for ( var y = 0; y < height; y++ ) {
     // Every (x, y) coordinate is looped here:
     var index = (x + y * width) * 4;
     pixels[index] = 255;     // red
     pixels[index+1] = 0;     // green
     pixels[index+2] = 0;     // blue
     pixels[index+3] = 255;   // alpha

In this example above every pixel is set to full red, no green, no blue and full transparency.


  • Add the 12_pixel_array directory to Atom
  • Open index.html in a browser
  • Change the RGBA values of the pixels inside the nested for loop
  • Try using the random() function to set the colour values
  • Try using the x and y variables to set the colour values

Image pixel data

Supporting Code
The code to support this section is located in the following directory and is available to view on Github:

Use a local web server
p5.js cannot access the image pixel data from an image that is loaded directly from the file system. Therefore you will need to install and run a HTTP server in order to complete the next exercise. To set up an local web server follow these instructions.

So far we have been manipulating the pixel colour values of an empty canvas; or more precisely a canvas full of a single colour. The exact same process is possible but instead of manipulating an empty canvas we can manipulate image data loaded in from an external file.

The data that represents an image is also made up of individual pixels (this is called a raster graphic and therefore within p5.js we access the image pixel data in the exact same way as we have already been accessing pixels in an array. Here is an example of this using a loaded image:

var img;

function preload() {
  img = loadImage("images/maxernst.jpg");

function mouseDragged(){
  var index = (mouseX + mouseY * width)*4;

  var r = img.pixels[index];
  var g = img.pixels[index+1];
  var b = img.pixels[index+2];
  var a = img.pixels[index+3];

  fill(r, g, b, a);
  ellipse(mouseX, mouseY, 40, 40);

You will notice a new function being used called preload(). This is a handy function provided by p5.js that ensures that images or external data such as API data are finished loading before calling the setup() and draw() functions:

Inside the preload function we give a relative path as an argument to the loadImage() function. The results of this are stored in a global variable img.

var img;

function preload() {
  img = loadImage("images/maxernst.jpg");

Then later in our draw() function we can access the pixel array as a property of the img object. We do this using the dot syntax. Here I am setting the first pixels colour to green:

img.pixel[0] = 0;
img.pixel[1] = 255;
img.pixel[2] = 0;


  • Add the 13_pixel_array directory to Atom
  • Set up a local web server and run it within the 13_pixel_array directory.
  • Open the URL provided by the local web server in a browser.
  • Click and drag the mouse around the canvas to see the pixel colours being rendered in circles
  • Uncomment the lines in the nested for loop and play with the rgba values:
img.pixels[index] = r;
img.pixels[index+1] = g;
img.pixels[index+2] = b;
img.pixels[index+3] = a;

Webcam capturing

The code to support this section is located in the following directory and is available to view on Github:

Using a local web server
This is another instance when you won't be able to run this sketch directly from your filesystem, you will need a local web server running. To set up an local web server follow these instructions.

Using p5.js accessing the webcam is quite straightforward. It takes just a few lines of code:

var capture;

function setup() {
  createCanvas(400, 300);

  // Create video capture object.
  capture = createCapture(VIDEO);
  capture.size(width, height);

function draw() {
  // Draw capture to the canvas.
  image(capture, 0, 0, width, height);

Behind the scenes the createCapture() function does a few clever things. Firstly it causes the browser to ask the user if they want their camera to be opened and used. This is a security provision to ensure nefarious programmers cannot access webcams without permission. Secondly it creates a HTML Video element in the browser and places it next to our p5.js canvas. We can then use the image data from inside that HTML Video object to draw into our canvas.

See this in action on CodePen.

However this leaves us with two copies of the webcam video. That is why we call capture.hide() in all the following examples.

What is extremely useful about this object stored in the capture variable is that the pixels inside it can be treated exactly the same as the pixel array and image pixel array examples.

for ( var x = 0; x < width; x++ ) {
  for ( var y = 0; y < height; y++ ) {
    // Get the pixel at x and y position
    var index = (x + y * width) * 4;
    capture.pixels[index] = 255;     // red
    // capture.pixels[index+1] = 0;   // green
    // capture.pixels[index+2] = 0;   // blue
    // capture.pixels[index+3] = 0;   // alpha  
image(capture, 0, 0, width, height);

In this example above every pixels has had it's red value cranked up to maximum giving the captured image a distinctly red tint.

Within the exercise code you will also find a call to the saveCanvas() function being used within the keyPressed() function:

function keyPressed(){
  if (keyCode == RETURN) {
    saveCanvas("webcam", "jpg");

This 4 lines of code allows the webcam image to be saved and downloaded as a JPG when the return key is pressed.


  • Add the 16_webcam_capture directory to Atom
  • Set up a local web server and run it within the 16_webcam_capture directory.
  • Open the URL provided by the local web server in a browser.
  • Hit the enter key to download a frame of the webcam video
  • Uncomment the lines in the nested for loop and play with the rgba values:
capture.pixels[index] = 255;     // red
capture.pixels[index+1] = 255;   // green
capture.pixels[index+2] = 255;   // blue
capture.pixels[index+3] = 255;   // alpha
Workshop: Introduction to Creative Coding

Week 4 - Other inputs and APIs


  • Independently researching new features of p5.js using the documentation
  • Using inputs to control behaviour of your sketch
  • Understanding the concept of web-based APIs and basic use
  • In groups create a sketch that uses either at least one input (learnt today) or APIs to create an interactive sketch

Local web server

So far during this series of workshops testing your code has involved opening the index.html file in your browser, which results in an absolute file path in the browser address bar (see below). You can see this indicated by the file:// protocol followed by the absolute file path to the index.html file:

For some examples you will need to run a local HTTP web server that serves the files in a project. If you have Node.js already installed you can run the following command to install an HTTP web server:

sudo npm install -g http-server

If you receive an error from the above command it's likely that you do not have Node.js installed. In which case visit the Node.js homepage and download/install the LTS version and repeat the command above.

Once you have installed the HTTP web server you will need to change directory (cd) into the project directory on the command line and run the server:

cd ~/Desktop/intro-to-programming-2017/15_image_pixel_array/

If successful you will see messages in the command line similar to this:

You can then copy and paste one of the URLs into you browser:

Other Inputs

So far you have used the input for mouse position to affect the visual output in your sketch.

There are a range of other inputs we can use to create dynamic / interactive sketches:

  • Click
  • Keyboard
  • Touch / Drag
  • Rotation

Experiment with these other inputs using the p5.js reference. Search for ‘Events’ section in the reference.


Supporting Code
The code to support this section is located in the following directory and is available to view on Github:

Here are a list of APIs you can use for this example:




Other workshops

Other workshops

Creative Coding 101

The following are the slides from Creading Coding 101, an introductory half day programming taster workshop.

Creative Coding 101 (PDF)