Shows the difference between constrain and map functions in Processing

constrain_vs_map.pde

// Constrain vs map v1
// Steve Lambert 2016-09-20

// variables
int ball1fill; // ball #1 fill color
int ball2fill; // ball #2 fill color

void setup(){
 size(500,300);
 background(0);
}


void draw(){ 
  background(255,0,0);
  stroke(125);
  line(255,0,255,height);
  noStroke();
  
// Ball #1 - Constrain
  // first, we're going to use constrain
  // to limit the fill color to 255.
  // Anything over 255 is 255
  ball1fill = constrain(mouseX,0,255);
  fill(ball1fill);
  ellipse(mouseX,(height/2)-50, 50,50);

// Ball #2 - Map
  // here we'll use map to convert the mouseX
  // position from 0 to width, to 0-255. 
  ball2fill = int(map(mouseX,0,width,0,255));
  // we need to add int(...) to change the number map
  // gives us from a float to a simle integer
  fill(ball2fill);
  ellipse(mouseX,(height/2)+50, 50,50);
  
// Some println so you can see it as it happens...
  println("mouseX: " + mouseX);
  println("ball1 Fill: " + ball1fill);
  println("ball2 Fill: " + ball2fill);
  
} //draw