learnxinyminutes-docs/processing.html.markdown

language	filename	contributors
Processing	learnprocessing.pde	Phone Thant Ko http://github.com/phonethantko

Introduction

Processing is a programming language for creation of digital arts and multimedia content, allowing non-programmers to learn fundamentals of computer programming in a visual context.
While the language is based on Java language, its syntax has been largely influenced by both Java and Javascript syntaxes. See more here
The language is statically typed, and also comes with its official IDE to compile and run the scripts.

/* ---------
   Comments
   ---------
*/

// Single-line comment starts with //

/*
   Since Processing is based on Java,
   the syntax for its comments are the same as Java (as you may have noticed above)!
   Multi-line comments are wrapped as seen here.
*/

/* ---------------------------------------
   Writing and Running Processing Programs
   ---------------------------------------
 */

// In Processing, your program's entry point is a function named setup() with a void return type.
// Note! The syntax looks strikingly similar to that of C++.
void setup() {
  // This prints out the classic output "Hello World!" to the console when run.
  println("Hello World!"); // Another language with a semi-column trap, ain't it?
}

// Normally, we put all the static codes inside the setup() method as the name suggest since it only runs once.
// It can range from setting the background colours, setting the canvas size.
// You will see more of them throughout this document.

// If you want to run the codes indefinitely, it has to be placed in draw() method.
// draw() must exist if you want the code to run continuously and obviously, there can only be one draw() method.
int i = 0;
void draw() {
  // This block of code loops forever until stopped
  print(i);
  i++; // Increment Operator!
}

// Now that we know how to write the working script and how to run it,
// we will proceed to explore what data types and collections are supported in Processing.

/* ------------------------
   Datatypes & collections
   ------------------------
*/

// According to Processing References, Processing supports 8 primitive datatypes as follows.

boolean booleanValue = true; // Boolean
byte byteValueOfA = 23; // Byte
char charValueOfA = 'A'; // Char
color colourValueOfWhiteM = color(255, 255, 255); // Colour (Specified using color() method)
color colourValueOfWhiteH = #FFFFFF; // Colour (Specified using hash value)
int intValue = 5; // Integer (Number without decimals)
long longValue = 2147483648L; // "L" is added to the number to mark it as a long
float floatValue = 1.12345; // Float (32-bit floating-point numbers)
double doubleValue = 1.12345D; // Double (64-bit floating-point numbers)

// NOTE!
// Although datatypes "long" and "double" work in the language,
// processing functions do not use these datatypes, therefore
// they need to be converted into "int" and "float" datatypes respectively,
// using (int) and (float) syntax before passing into a function.

// There is a whole bunch of default composite datatypes available for use in Processing.
// Primarily, I will brief through the most commonly used ones to save time.

// String
// While char datatype uses '', String datatype uses "" - double quotes.
String sampleString = "Hello, Processing!";
// String can be constructed from an array of char datatypes as well. We will discuss array very soon.
char source = {'H', 'E', 'L', 'L', 'O'};
String stringFromSource = new String(source); // HELLO
// As in Java, strings can be concatenated using the "+" operator.
print("Hello " + "World!"); // Hello World!

// Array
// Arrays in Processing can hold any datatypes including Objects themselves.
// Since arrays are similar to objects, they must be created with the keyword "new".
int[] intArray = new int[5];
int[] intArrayWithValues = {1, 2, 3}; // You can also populate with data.

// ArrayList
// Functions are similar to those of array; arraylists can hold any datatypes.
// The only difference is arraylists resize dynamically,
// as it is a form of resizable-array implementation of the Java "List" interface.
ArrayList<Integer> intArrayList = new ArrayList<Integer>();

// Object
// Since it is based on Java, Processing supports object-oriented programming.
// That means you can basically define any datatypes of your own and manipulate them to your needs.
// Of course, a class has to be defined before for the object you want.
// Format --> ClassName InstanceName
SomeRandomClass myObject // then instantiate later
//or
SomeRandomClass myObjectInstantiated = new SomeRandomClass();

// Processing comes up with more collections (eg. - Dictionaries and Lists) by default,
// for the simplicity sake, I will leave them out of discussion here.

/* ------------
   Maths
   ------------
*/

// Arithmetic
1 + 1 // 2
2 - 1 // 0
2 * 3 // 6
3 / 2 // 1
3.0 / 2 // 1.5
3.0 % 2 // 1.0

// Processing also comes with a set of functions that simplify mathematical operations.
float f = sq(3); // f = 9.0
float p = pow(3, 3); // p = 27.0
int a = abs(-13) // a = 13
int r1 = round(3.1); // r1 = 3
int r2 = round(3.7); // r2 = 4
float sr = sqrt(25); // sr = 5.0

// Vectors
// Processing provides an easy way to implement vectors in its environment using PVector class.
// It can describe a two or three dimensional vector and
// comes with a set of methods which are useful for matrices operations.
// You can find more information on PVector class and its functions here.
// (https://processing.org/reference/PVector.html)

// Trigonometry
// Processing also supports trigonometric operations by supplying a set of functions.
// sin(), cos(), tan(), asin(), acos(), atan() and also degrees() and radians() for convenient conversion.
// However, those functions take angle in radians as the parameter so it has to be converted beforehand.
float one = sin(PI/2); // one = 1.0
// As you may have noticed, there exists a set of constants for trigonometric uses;
// PI, HALF_PI, QUARTER_PI and so on...

/* -------------
   Control Flow
   -------------
*/

// Conditional Statements
// If Statements - The same syntax as if statements in Java.
if (author.getAppearance().equals("hot")) {
  print("Narcissism at its best!");
} else {
  // You can check for other conditions here.
  print("Something is really wrong here!");
}
// A shortcut for if-else statements can also be used.
int i = 3;
String value = (i > 5) ? "Big" : "Small"; // "Small"

// Switch-case structure can be used to check multiple conditions more concisely.
int value = 2;
switch(value) {
  case 0:
    print("Nought!"); // This doesn't get executed.
    break; // Jumps to the next statement
  case 1:
    print("Getting there..."); // This again doesn't get executed.
    break;
  case 2:
    print("Bravo!"); // This line gets executed.
    break;
  default:
    print("Not found!"); // This line gets executed if our value was some other value.
    break;
}

// Iterative statements
// For Statements - Again, the same syntax as in Java
for(int i = 0; i < 5; i ++){
  print(i); // prints from 0 to 4
}

// While Statements - Again, nothing new if you are familiar with Java syntax.
int j = 3;
while(j > 0) {
  print(j);
  j--; // This is important to prevent from the code running indefinitely.
}

// loop()| noLoop() | redraw() | exit()
// These are more of Processing-specific functions to configure program flow.
loop(); // allows the draw() method to run forever while
noLoop(); // only allows it to run once.
redraw(); // runs the draw() method once more.
exit(); // This stops the program. It is useful for programs with draw() running continuously.

Since you will have understood the basics of the language, we will now look into the best part of Processing; DRAWING.

Processing is easy to learn and is particularly useful to create multimedia contents (even in 3D) without having to type a lot of codes. It is so simple that you can read through the code and get a rough idea of the program flow.
However, that does not apply when you introduce external libraries, packages and even your own classes. (Trust me! Processing projects can get really large)

What's Next?

Here, I have compiled some useful resources:

• Processing Website
• Processing Sketches