'cmap defaults to its rc setting
cmap is a colors.Colormap instance
norm is a colors.Normalize instance to map luminance to 0-1
Additional kwargs are matplotlib.artist properties'

def __init__(self, ax, x=None, y=None, A=None, cmap=None, norm=None, **kwargs):

    super(PcolorImage, self).__init__(ax, norm=norm, cmap=cmap)
    self.update(kwargs)
    if (A is not None):
        self.set_data(x, y, A)
