Which processing technique will amplify particular known frequencies in an image while suppressing others?

• A. Frequency-domain filtering
• B. Spatial-domain filtering
• C. All the above
• D. Histogram equalization

Answer: (C)

The main idea is to target and modify specific spatial frequencies in an image. To amplify particular frequencies while suppressing others, you apply a filter that has a frequency response focused on the desired band. In the frequency domain, you explicitly multiply the image’s spectrum by a mask that passes the frequencies you want and attenuates the rest, then inverse-transform back to the image. In the spatial domain, you can design a convolution kernel whose effect corresponds to a band-pass (or other selective) filter; convolving the image with that kernel enhances the chosen frequencies while dampening others. Histogram equalization, while not a frequency-selective operation, changes the distribution of intensities to improve overall contrast and can alter the texture and edges, which in turn can subtly influence the spectrum. Because all these processes can influence frequency content in some way, the option that includes all of them is considered correct.