'**SUMMARY**
Return a grayscale Numpy array of the image.
**RETURNS**
Returns the image, converted first to grayscale and then converted to a 2D numpy array.
**EXAMPLE**
>>> img = Image("lenna")
>>> rawImg  = img.getGrayNumpy()
**SEE ALSO**
:py:meth:`getEmpty`
:py:meth:`getBitmap`
:py:meth:`getMatrix`
:py:meth:`getPIL`
:py:meth:`getNumpy`
:py:meth:`getGrayNumpy`
:py:meth:`getGrayscaleMatrix`'

def getGrayNumpy(self):

    if (self._grayNumpy != ''):
        return self._grayNumpy
    else:
        self._grayNumpy = uint8(np.array(cv.GetMat(self._getGrayscaleBitmap())).transpose())
    return self._grayNumpy
