lineDetect

def lineDetect(orig, threshold):
# @param orig: pict; immagine di partenza
# @param threshold: int (for most pictures, good results for values <50)
# @return pict
  makeBw = duplicatePicture(orig)
  for x in range(0,getWidth(orig)-1):
    for y in range(0, getHeight(orig) -1):
      here=getPixel(makeBw,x,y)
      down=getPixel(orig,x,y+1)
      right=getPixel(orig, x+1,y)
      hereLum=(getRed(here)+getGreen(here)+getBlue(here))/3
      downLum=(getRed(down)+getGreen(down)+getBlue(down))/3
      rightLum=(getRed(right)+getGreen(right)+getBlue(right))/3
      if abs(hereLum-downLum)>threshold and abs(hereLum-rightLum)>threshold:
        setColor(here ,black)
      if abs(hereLum-downLum)<=threshold or abs(hereLum-rightLum)<=threshold:
        setColor(here ,white)

  return makeBw