The Research Of Hue Enhancement Technology For Color Image

With the development of the Computer capability, the maturity of multimedia technology, and especially the development of the color imaging device, color image processing technology becomes more and more important. Especially in display field, the newly emerging LCD display has many advantages such as portability, less consumption of power, no radiation, high definition, high brightness and abundant interfaces. But due to the defect of the color expression, more and more people devoted to the color image enhancement technology of LCD. According to this problem, this paper mainly improves the LCD image processing cell by processing the luminance, contrast and saturation of color image to improve the color expressive ability.Based on the introduction of the background and significance of the subject, this paper explaines the development trend of color image enhancement briefly. Then introduced the basic principles of human vision, the factor of human vision and basic knowledge of colorimetry.The conventional spatial domain enhancement methods of the gray image include linear transformation, nonlinear transformation, histogram correction, smoothing filtering and sharp filtering. In this paper these algorithms are applied to color image processing and their advantages and disadvantages are analyzed.For luminance component, a new method of color image enhancement based on the wavelet transform is proposed. In HSV space which accord with human visual system, the low frequency coefficient and high frequency coefficient of the luminance component which are decomposed by wavelet are processed respectively according to their different properties. For the high frequency coefficient which expresses image details, we use the local variance to divide the high frequency component into smooth region, medium contrast region and high contrast region. Based on the human visual properties, in the smooth region which is sensitive to noise, we do nothing. In medium contrast region and high contrast region, we use the nonlinear unsharp masking method which has different enhance coefficient, this method can enhance the local information of images and also can restrain the noise. For the low frequency coefficient which expresse the general appearance of image, we use the nonlinear mapping function to enhance the global contrast and luminance of image. The saturation component of color image is enhanced by an exponential function. After processing, the image's luminance, details and color expression are improved.In addition, according to saturation segmentation algorithm, a new saturation enhancement algorithm with luminance component is proposed. In HSV space, the saturation component is divided into four regions: very-high saturation, high saturation, low saturation and very-low saturation. The different saturation regions are processed using a different adjustment curve because the different visual induction for saturation colour. For the high saturation and low saturation regions, we use positive enhancement to improve the saturation, and for the very-high saturation region, we use negative enhancement to properly reduce the saturation. Finally, from the luminance-saturation correlation coefficient, the luminance feedback were proposed for a further treatment of the saturation component, thus the saturation is more accord with the human visual perception. Then the color saturation distortion image can be enhanced by choosing proper parameters.