your code

HTML

<script src="http://4.bp.blogspot.com/_Afm6-TcZ7Ho/S67FnPJD0_I/AAAAAAAAC6I/giTT8ePty5E/s1600/bunny.jpg"></script>
<script src="http://bigbackground.com/wp-content/uploads/2013/05/baby-wolf-backgrounds.jpg"></script>
<script type="application/processing">
/* <a rel="nofollow" href="/two/profile/pjs">@pjs</a> preload="http://4.bp.blogspot.com/_Afm6-TcZ7Ho/S67FnPJD0_I/AAAAAAAAC6I/giTT8ePty5E/s1600/bunny.jpg, http://bigbackground.com/wp-content/uploads/2013/05/baby-wolf-backgrounds.jpg"; 
 */
 
 
 
/*
*
 *
 */
 
 
PGraphics maskPattern;
PGraphics savedimg;
PImage img1;
PImage img2;
 
int displayImageX;
int displayImageY;
 
float scaleFactor;
float centerScaledAdjustedXpos;
float centerScaledAdjustedYpos;
 
void setup() {
  img1 = loadImage("http://4.bp.blogspot.com/_Afm6-TcZ7Ho/S67FnPJD0_I/AAAAAAAAC6I/giTT8ePty5E/s1600/bunny.jpg");
  size(800, 800, JAVA2D);
  //640,260
  maskPattern = createGraphics(img1.width, img1.height);
  savedimg = createGraphics(img1.width, img1.height);
  img2 = loadImage("http://bigbackground.com/wp-content/uploads/2013/05/baby-wolf-backgrounds.jpg");
 
  scaleFactor=1;
 
  displayImageX = width/2;
  displayImageY = height/2;
 
  centerScaledAdjustedXpos=0;
  centerScaledAdjustedYpos=0;
}
 
void draw() {
 
  pushMatrix();
  scale(scaleFactor);
 
 
  background(0);
 
  imageMode(CENTER);
  image(img2, displayImageX/scaleFactor, displayImageY/scaleFactor);
 
 
 
  if (mousePressed == true) {
    maskPaint();
  }
 
 
  img1.mask(maskPattern);
 
  image(img1, displayImageX/scaleFactor, displayImageY/scaleFactor);
 
 
 
 
  popMatrix();
}
 
 
void maskPaint() {
 
 
  centerScaledAdjustedXpos = ((mouseX-displayImageX)/scaleFactor+(maskPattern.width/2));
  centerScaledAdjustedYpos = ((mouseY-displayImageY)/scaleFactor+(maskPattern.height/2));
 
  maskPattern.beginDraw();
  maskPattern.stroke(255);
  maskPattern.fill(255);
  maskPattern.ellipse(centerScaledAdjustedXpos, centerScaledAdjustedYpos, 50, 50);
 
 
 
 
  maskPattern.endDraw(); 
 
 ...

JavaScript

var scripts=document.getElementsByTagName("script");
for(var i=0;i<scripts.length;i++) {
    if(scripts[i].type=="application/processing"){
        var src=scripts[i].src,canvas=scripts[i].nextSibling;
        if(src&&src.indexOf("#")){
           canvas=document.getElementById(src.substr(src.indexOf("#")+1));
        }else{
            while(canvas&&canvas.nodeName.toUpperCase()!="CANVAS")
                canvas=canvas.nextSibling;
        }
        if(canvas){
            new Processing(canvas,scripts[i].text);
        }
    }
}