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Low complexity multifocus image fusion in discrete cosine transform domain

Phamila A V, Amutha R

Optica Applicata

2013

Vol. 43, nr 4

693--706

This paper presents a low complex, highly energy efficient sensor image fusion scheme explicitly designed for wireless visual sensor systems equipped with resource constrained, battery powered image sensors and employed in surveillance, hazardous environment like battlefields etc. Here an energy efficient simple method for fusion of multifocus images based on higher valued AC coefficients calculated in discrete cosine transform domain is presented. The proposed method overcomes the computation and energy limitation of low power devices and is investigated in terms of image quality and computation energy. Simulations are performed using Atmel ATmega128 processor of Mica 2 mote, to measure the resultant energy savings and the simulation results demonstrate that the proposed algorithm is extremely fast and consumes only around 1% of energy consumed by conventional discrete cosine transform based fusion schemes. Also the simplicity of our proposed method makes it more appropriate for real-time applications.

The discrete cosine transform (DCT) plus local normalization: a novel two-stage method for de-illumination in face recognition

Zhao M., Wang Y., Shi Z., Zhang J.

Optica Applicata

2011

Vol. 41, nr 4

825--839

To deal with illumination variations in face recognition, a novel two-stage illumination normalization method is proposed in this paper. Firstly, a discrete cosine transform (DCT) is used on the original images in logarithm domain. DC coefficient is set based on the average pixel value of all the within-class training samples and some low frequency AC coefficients are set to zero to eliminate illumination variations in large areas. Secondly, local normalization method, which can minimize illumination variations in small areas, is used on the inverse DCT images. This makes the pixel values on the processed images be close to or equal to that of the normal illumination condition. Experimental results, both on Yale B database and Extended Yale B database, show that the proposed method can eliminate effect of illumination variations effectively and improve performance of face recognition methods significantly. The present method does not demand modeling step and can eliminate the effect of illumination variations before face recognition. In this way, it can be used as a preprocessing step for any existing face recognition method.

Noise reduction for digital holograms in a discrete cosine transform (DCT) domain

Choi H. J., Seo Y. H., Kim D. W.

Optica Applicata

2010

Vol. 40, nr 4

991--1005

This paper presents a method for reducing noise in a digital hologram, which occurs during acquisition. The algorithm proposed initially transforms a digital hologram into frequency-domain data through a discrete cosine transform (DCT), and separates the object from the background in the transformed image. As a noise reduction method, a histogram modification method is applied to the object, while the background is substituted with zero values. Experimental results showed that the proposed scheme improves the visual image quality very much when reconstructed by both the optical system and the PC simulation.