Figure 6.

The divergence sign is indicated in the top-right corner in black, the $\widetilde{{\alpha }_i^j}$ is indicated in green and $\widetilde{{\alpha }_0^k}$ is indicated in blue. The divergence is computed at the centroid of all keypoints, indicated by the filled black circle. The divergence in (a) is small and the computed magnification factor, $\widetilde{{\alpha }_i^j}$, can be rejected. In (b) and (c) the divergence has large magnitude and the sign of divergence indicates whether the microscope’s zoom-in or the zoom-out function was used. Based on the magnitude of the divergence, the current magnification factor, $\widetilde{{\alpha }_i^j}$, is accepted for reliably changing the overall magnification factor, $\widetilde{{\alpha }_0^k}$ .