float percent = 1.0;
int  originalwidth = 500;
int  originalheight = 246;
float newwidth = originalwidth;
float newheight = originalheight;

PImage img; 
void setup() { 
  size(500, 246); 
  background(255);
  img = loadImage("CalmAngry500at300.jpg"); 
 fill(153);
} 

void mouseMoved(){
   newwidth = constrain(2 * abs(mouseX - (originalwidth / 2)), 1, originalwidth);
   float percent = newwidth / originalwidth;
   newheight = originalheight * percent; 
}

void draw(){
 background(255);

      image(img,(originalwidth - newwidth)/2,(originalheight-newheight)/2,newwidth,newheight);

}