Quite simple: load image into a variable of type PImage, paint it, then call mouseClicked() to increment a rotation amount.

PImage pim;
float rot=0;
void setup(){
 pim = loadImage("http://processing.org/img/processing_beta_cover.gif");
}
void draw(){
 background(255);
 translate(width/2, height/2);
 rotate(rot);
 image(pim,-pim.width/2,-pim.height/2);
}
void mouseClicked(){
 rot+=PI/2;
}

I have a similar problem, I need to move an image but in a 3d sense, I have been through the References and I don't know what to pick. Right now I have a disc, with a smaller one inside which I would like to animate, moving it left and round to the front, how would I achieve this?


// Location of moving circle to start with (stationary)
int circleX = 300;
int circleY = 241;

//size of page
void setup() {
 size(600,600);
 smooth();


 // Disc
fill(255);
ellipse(300,250,160,30);

 // Moving circle shape size and colour details
 stroke(0);
 fill(122, 222, 33);
 ellipse(circleX,circleY,22,6);
}