def _compute_fluxes(self):
        """
        Compute integrated flux inside ellipse, as well as inside a
        circle defined with the same semimajor axis.

        Pixels in a square section enclosing circle are scanned; the
        distance of each pixel to the isophote center is compared both
        with the semimajor axis length and with the length of the
        ellipse radius vector, and integrals are updated if the pixel
        distance is smaller.
        """

        # Compute limits of square array that encloses circle.
        sma = self.sample.geometry.sma
        x0 = self.sample.geometry.x0
        y0 = self.sample.geometry.y0
        xsize = self.sample.image.shape[1]
        ysize = self.sample.image.shape[0]

        imin = max(0, int(x0 - sma - 0.5) - 1)
        jmin = max(0, int(y0 - sma - 0.5) - 1)
        imax = min(xsize, int(x0 + sma + 0.5) + 1)
        jmax = min(ysize, int(y0 + sma + 0.5) + 1)

        # Integrate
        if (jmax-jmin > 1) and (imax-imin) > 1:
            y, x = np.mgrid[jmin:jmax, imin:imax]
            radius, angle = self.sample.geometry.to_polar(x, y)
            radius_e = self.sample.geometry.radius(angle)

            midx = (radius <= sma)
            values = self.sample.image[y[midx], x[midx]]
            tflux_c = np.ma.sum(values)
            npix_c = np.ma.count(values)

            midx2 = (radius <= radius_e)
            values = self.sample.image[y[midx2], x[midx2]]
            tflux_e = np.ma.sum(values)
            npix_e = np.ma.count(values)
        else:
            tflux_e = 0.
            tflux_c = 0.
            npix_e = 0
            npix_c = 0

        return tflux_e, tflux_c, npix_e, npix_c
Compute integrated flux inside ellipse, as well as inside a
        circle defined with the same semimajor axis.

        Pixels in a square section enclosing circle are scanned; the
        distance of each pixel to the isophote center is compared both
        with the semimajor axis length and with the length of the
        ellipse radius vector, and integrals are updated if the pixel
        distance is smaller.