def diagonalLine(pict,startX,startY,c):
# @param pict:Picture
# @param startX:Int
# @param startY:Int
# @param c:Color
  if startX<0 and startX>=getWidth(pict):
    print "error in parameter setting; startX index out of range"
    return
  if startY<0 and startY>=getHeight(pict):
    print "error in parameter setting; startY index out of range"
    return

  # Now, make the diagonal line
  x=startX
  y=startY
  while x<getWidth(pict) and y<getHeight(pict):
    pix=getPixel(pict,x,y)
    setColor(pix,c)
    x=x+1
    y=y+1