title: Jython image manipulation
body: <p>This program is supposed to take the outline of an image, then split it into different quadrants, then color it, such as the Andy Warhol Marilyn Monroe picture.  </p>
  
  <p>Every function up to the "Warholize" function works but it gets stuck on <code>c=getPixel(picEdge,x,y)</code> under the <code>warholize</code> function at which I'm not sure what to do.  Any help would be greatly appreciated.  It is supposed to do "let c be the color of the pixel in picEdge at location x,y "</p>
  
  <pre><code>def main():
    pic= makePicture( pickAFile() )
    show( pic )
    threshold= 10
    edgePic= makeOutline( pic, threshold )
    warholize(pic)
    show(warholize(pic))
  
  def difference( a, b ):
    if a &gt; b :
      return a - b
    else:
      return b - a
  
  def intensity( px ) :
    r= getRed( px )
    g= getBlue( px )
    b= getGreen( px )
    avg= ( r + g + b ) / 3
    return avg
  
  def makeOutline( pic, threshold ):
    w= getWidth( pic )
    h= getHeight( pic )
    edgePic= makeEmptyPicture( w, h )
    for x in range(2,w-1) :
      for y in range(2,h-1):
        px= getPixel( pic, x, y )
        pxLeft= getPixel( pic, x-1, y )
        pxUp= getPixel( pic, x, y-1 )
        leftDiff= difference( intensity(pxLeft), intensity(px) )
        upDiff= difference( intensity(pxUp), intensity(px) )
        if leftDiff &gt; threshold or upDiff &gt; threshold :
          setColor( getPixel(edgePic,x,y), black )   
  
  def warholize(pic):
      threshold=10
      picEdge=makeOutline(pic,threshold)
      w= getWidth( pic )
      h= getHeight( pic )
      picNew= makeEmptyPicture( w, h )
  
      for x in range(0,w,2):
          for y in range (0,h,2):
             c=getPixel(picEdge,x,y)
             px=getPixel(picNew,x/2,y/2)
             if c is black:
                 setColor(px,blue)
             else:
                 setColor(px,yellow)
      return picNew
  </code></pre>