Band Pass Filters in Image Preprocessing

Assume you’re in your collage festival where various different artists perform at several different stages and each artist performs on different theme, there is mesh of sounds and music around you but you want to focus on energetic rock music coming from one specific stage, and filter other sounds which seems noise for you when you’re trying to focus is on particular type of music which is rock in our example, band pass acts as filter that keeps range of specific frequencies you want to hear clearly for better experience. Similarly in images whenever our objective is to highlight specific type of properties of image, band pass filter mask adjusts the settings, for attenuating frequencies outside the desired passband while allowing those within the passband to pass through with minimal change. With which we essentially “mute” the unwanted frequencies in the image, enhancing the details within the chosen frequency range.

What is Band pass filter?

As name suggests ‘band pass’ it means that it is type of filter in image preprocessing which pass only range (band) of frequencies within an image while attenuating frequencies outside that band. It is used for dropping certain frequency components from the image. For example, in aerial images it may use to highlight certain patterns from the image.

Popular band pass filters

Gaussian Bandpass Filter

Use Case: Commonly used for noise reduction while preserving edges and fine details.

Butterworth Bandpass Filter

Use Case: Commonly used for motion analysis

Chebyshev Bandpass Filter

Use Case: Commonly used for sharper transition between passband and stopband is required

FIR (Finite Impulse Response) Bandpass Filter

Use Case: Commonly used for biomedical signal processing, and seismic data analysis.

IIR (Infinite Impulse Response) Bandpass Filter:

Use Case: Commonly used where low latency is crucial.

Types of Band pass filters

Fourier Transform Based Filters

Wavelet Transform Based Filters

Spatial Domain Filters