Earticle

Scanned topographic maps of cities may have uneven illumination and creases. They need to go through color dodging. Due to the unsatisfying result by homomorphic filter of Retinex theory and the low efficiency when color dodging, this paper proposes an improved color dodging for scanned topographic maps based on Retinal-cortex theory. The main idea is to introduce Fastest Fourier Transform In The West (FFTW) to get the illumination component of the image on the basis of homomorphic filter of the Retinal-cortex algorithm, and use homomorphic filter to get the reflectance component and get the final image by linear stretching treatment. Experiments have proved that this method keeps the details of the image while erasing the creases so that the brightness distribution is improved.

In this paper, we present a new morphology-based homomorphic filtering technique for feature enhancement in medical images. The proposed method is based on decomposing an image into morphological subbands. The homomorphic filtering is performed using the morphological subbands. The differential evolution algorithm is applied to find an optimal gain and structuring element for each subband. Simulations show that the proposed filter improves the contrast of the features in medical images.

본 논문은 유방 조영 영상의 대비를 향상시키기 위해 새로운 호모몰픽 필터(MBHF)를 제안한다. 제안된 필터는 영상을 형체적으로 다수 분할한 후 각각의 형체 즉, 서브-밴드에 대해 그 구성요소와 이득이 차분진화를 통해 최적의 값을 갖도록 설계된다. 결과 분석을 통해 제안된 방법이 영상 대비를 향상시키는 것을 보이며 웨이블렛 기반의 호모몰픽 필터와 성능이 비교된다. 성능평가 기준으로는 인간의 시각적 인식을 고려한 WPSNR(Weighted Peak Signal to Noise Ratio)을 사용한다.

In this paper, a new MBHF(Morphology-Based Homomorphic filter) is presented to enhance contrast in mammographic images. The MBH filtering is performed based on the morphological sub-bands, in which an image is morphologically decomposed. The filter is designed to have optimal gain and structuring element in each sub-band through differential evolution. Experimental results show that the proposed method improves the contrast in mammographic images such that an evaluation criterion, WPSNR(Weighted Peak Signal to Noise Ratio) which takes into account human visual system is increased compared with a wavelet-based Homomorphic filter.

Hardware realization of a digital 2-D homomorphic filter for real time contrast enhancement of video signal is presented. In homomorphic filter, logarithmic and exponential conversion used the memory lookup table method and because the hardware is implemented by multiplierless TTL devices, it can be designed to specific IC. The contrast gain can be controlled externally and the transfer function of homomorphic filter can be easily varied by the change of lookup table memory data.

In this paper, a MMSE filter in homomorphic wavelet transform domain is proposed for restoring an ultrasonic images corrupted by speckle noise. In order to remove effectively the speckle noise which is a kind of multiplicative noise, speckle noise is transformed into a form of additive noise and then the additive noise is denoised through the MMSE filter in homomorphic wavelet transform domain. The proposed method shows much higher quality in terms of ISNR and subject quality.