Low-pass filter parameters for image downsampling

1. Should low-pass filter be before or after downsampling?
2. Why is low-pass filter used before downsampling?
3. What is ideal low-pass filter on image?
4. Can low-pass filter sharpen an image?

Should low-pass filter be before or after downsampling?

ABSTRACT. A LPF (low-pass-filter) will usually be used before down-sampling to reduce aliasing. In this document, we investigated the effect of the LPF by comparing the difference in frequency domain and human ear perception of the signal with/without passing though a LPF before down-sampling.

Why is low-pass filter used before downsampling?

You need to apply a lowpass filter before you downsample the signal to avoid "aliasing". The cutoff frequency of the lowpass filter should be less than the nyquist frequency, which is half the sample frequency.

What is ideal low-pass filter on image?

In the field of Image Processing, Ideal Lowpass Filter (ILPF) is used for image smoothing in the frequency domain. It removes high-frequency noise from a digital image and preserves low-frequency components. from the origin without attenuation and cuts off all the frequencies outside the circle.

Can low-pass filter sharpen an image?

Low pass filter: Low pass filter is the type of frequency domain filter that is used for smoothing the image. It attenuates the high frequency components and preserves the low frequency components. High pass filter: High pass filter is the type of frequency domain filter that is used for sharpening the image.