Image contrast enhancement by homomorphic filtering in frequency field
Ang Y · 2007
In digital image processing, the homomorphic filtering approach is derived from an illumination-reflectance model of the image. Homomorphic filtering can perform simultaneous dynamic range compression and contrast enhancement. Crucial for the success of the homomorphic approach is the selection of an appropriate frequency-domain filter function in order to modify the illumination and reflectance components of an image differently. The author used Butterworth equations, Gaussian equations and Exponent equation to enhance image contrast by modifying Butterworth type highpass equations, Gaussian type highpass equations and Exponent type highpass equation. The Butterworth homomorphic filtering equations far superior to other frequency-domain filter functions, including Gaussian equations, making the Butterworth homomorphic suitable for use with the homomorphic filtering approach.