Figure 4.

Test data sharpening using a Gaussian filter. Test data is first denoised using a Gaussian filter (①) using the $\sigma$ parameter (②), and the denoised result is subtracted from the test data to obtain sharped details (③). The sharpened details are then amplified to some degree using $\alpha$ parameter (④) and added to the original test data to obtain sharpened test data (⑤).