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SUMMARYPoor illumination and viewing conditions have negativeinfluences on the quality of an image, especially the contrast of the dark and bright region. Thus, captured and displayed images usually need contrast enhancement. Histogram-based or gamma correction-based methods are generally utilized for this. However, these methods are global contrast enhancement method, and since the sensitivity of the human eye changes locally according to the position of the object and the illumination in the scene, the global contrast enhancement methods have a limit. The spatial adaptive method is needed to overcome these limitations and it has led to the development of an integrated surround retinex (ISR), and estimation of dominant chromaticity (EDC) methods. However, these methods are based on Gray-World Assumption, and they use a general image formation model, so the color constancy is known to get poor results, shown through graying-out, halo-artifacts (ringing effects), and the dominated color. This paper presents a contrast enhancement method using a modified image formation model in which the image is divided into three components: global illumination, local illumination and reflectance. After applying the power constant value to control the contrast in the resulting image, the output image is obtained from their product to avoid or minimize a color distortion, based on the sRGB color representation. The experimental results show that the proposed method yields better performances than conventional methods. key words: modified image formation model, global illumination, local illumination, reflectance, JND-based adaptive smoothing method

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This paper presents a novel error concealment method using inter-layer correlation in multilayer video coding. The proposed method enhances the image quality by rejecting the high frequency component around the block boundary using the inter-block correlation of the reference layer and by preserving the original edge component considering the frequency features of neighbor blocks. The simulations show that the subjective quality and PSNR of the concealed image is high.

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