A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Balasaraswathi, M.
- Quantitative Evaluation for Contrast Enhancement and Image Qualities Measurement
Authors
1 Anna University, Tamilnadu, IN
2 Department of Electronics and Communication, Anna University, Tamilnadu, IN
Source
Digital Image Processing, Vol 4, No 6 (2012), Pagination: 327-336Abstract
Histogram equalization, which aims at information maximization, is widely used in different ways to perform contrast enhancement in images. In this paper, an automatic exact histogram specification technique is proposed and used for global and local contrast enhancement of images. The desired histogram is obtained by first subjecting the image histogram to a modification process and then by maximizing a measure that represents increase in information and decrease in ambiguity. A new method of measuring image contrast based upon local band-limited approach and center-surround retinal receptive field model is also devised in this paper. This method works at multiple scales (frequency bands) and combines the contrast measures obtained at different scales using Lp-norm. In comparison to a few existing methods, the effectiveness of the proposed automatic exact histogram specification technique in enhancing contrasts of images is demonstrated through qualitative analysis and the proposed image contrast measure based quantitative analysis.Keywords
Ambiguity Measures, Beam Theory, Center-Surround Retinal Receptive Field, Contrast Enhancement, Exact Histogram Specification, Local Band-Limited Contrast.
- A Down Sampling Approach Technique for Design Hilbert-Pair of Wavelets
Authors
1 Anna University, Tamilnadu, IN
Source
Digital Signal Processing, Vol 4, No 6 (2012), Pagination: 269-272Abstract
To design the pair of conjugate Quadrature filter banks, whose corresponding wavelets are Hilbert transform of each other. The Transfer function of the CQF-(conjugate Quadrature filer) is having common factor and the phase factor. The phase factor is designed using Park-McClellan algorithm and down sampling approach with different frequencies specifications. The common factor is present in both filter banks. The phase factor with down sampling approach provides the sharper frequency response for CQF (Conjugate Quadrature filter). The sharper response filters provides the good Hilbert pair of wavelets, with desire properties of wavelets .The design of Hilbert pair of wavelets with same vanishing moments and same degree of phase factor with different frequency specification is analysed here.