A simple app for learning how scale() and translate() work.

scaletranslate.pde

// I, Brandon Martin-Anderson, release this into the public domain.
// Do whatever you want with it.

// A simple app for learning how scale() and translate() work.
// Left click and drag to scale.
// Right click and drag to translate.
// Spacebar to switch to between translate-first, and scale-first.

float xscale=1;
float yscale=1;
float xtrans=0;
float ytrans=0;

void setup() {
  size(500,500);
}

boolean scalefirst=false;

void mouseDragged() {
  if(mouseButton==37){
    xscale += (mouseX-pmouseX)*0.01;
    yscale += (mouseY-pmouseY)*0.01;
  }
  if(mouseButton==39){
    xtrans += (mouseX-pmouseX);
    ytrans += (mouseY-pmouseY);
  }
  
  println( "["+xscale+","+yscale+"] ["+xtrans+","+ytrans+"]" );
}

void keyPressed() {
  if( key==' ' ) {
    scalefirst = !scalefirst;
  }
  
}

void draw() {
  if(scalefirst) {
    scale(xscale,yscale);
    translate(xtrans,ytrans);

  } else {
    translate(xtrans,ytrans);
    scale(xscale,yscale);
  }

  background(255);
  rect( -100, -100, 200, 200 );
  line(0,0,100,100);
  line(0,-100,0,100);
  line(-100,0,100,0);
}