def circleFrame(pic,radius):
  width=getWidth(pic)
  height=getHeight(pic)
  for i in range(0,width):
    for j in range(0,height):
      #  if pixel location is more than radius from center we set the pixel to black
      if dist(i,j,width/2.0,height/2.0)> radius:
        p=getPixel(pic,i,j)
        setColor(p,black)  
  return

def circleWipe(pic,numFrames):
  maxRadius=dist(getWidth(pic)/2.0,getHeight(pic)/2.0,0,0)
  print maxRadius
  outPic=duplicatePicture(pic)
  writePictureTo(outPic, "frame"+"0"*len(str(numFrames-1))+".bmp")
  for i in range(1,numFrames): 
    radius = maxRadius* (1.0 - float(i)/float(numFrames-1))
    circleFrame(outPic,radius)
    writePictureTo(outPic,"frame"+"0"*(len(str(numFrames-1))-len(str(i)))+str(i)+".jpg")
  return   

def dist(x,y,u,v):
  distSquared=(x-u)*(x-u)+(y-v)*(y-v)
  return(sqrt(float(distSquared)))