code: #runas: import numpy as np ; N = 500 ; X = np.random.randn(N,N,3); laplacien(X)
  #pythran export laplacien(float64[][][3])
  
  import numpy as np
  def laplacien(image):
      out_image = np.abs(4*image[1:-1,1:-1] -
                                     image[0:-2,1:-1] - image[2:,1:-1] -
                                     image[1:-1,0:-2] - image[1:-1,2:])
      valmax = np.max(out_image)
      valmax = max(1.,valmax)+1.E-9
      out_image /= valmax
      return out_image
  
apis: numpy.max numpy.abs