The image quality improvement techniques based on Retinex theorem are effective for enhancement of visibility in dark area, while visibility in bright area is degraded. This paper presents an image fusion technique using source image and Retinex-processed image in order to implement high visibility in both bright and dark areas. In the proposed method, the statistic that corresponds to the subject's evaluation is used for image fusion. It is shown through some experiments that the proposed method can generate the image with high visibility in both bright and dark areas, with less computational cost compared with a conventional image fusion method.
K E Y W O R D Shigh visibility, image fusion, image quality improvement, rescaling SSR, Retinex 52
SUMMARYIn the field of digital signal processing, there are cases in which the frequency characteristics must be changed instantaneously in response to the processing objective. A filter whose characteristic can be varied instantaneously is called a variable filter. Many reports are available on the design of FIR digital filters with a variable passband. However, it appears that there are no publications on the design of an FIR digital filter in which the portion of the stopband with high attenuation can be varied. In this paper, a design method is proposed for an FIR digital filter using spectral parameters that make the portion of the stopband with high attenuation variable. For the design, the successive projection method with a simple algorithm is applied. A filter with an almost equal-ripple profile for the entire amplitude characteristic is designed by varying the spectral parameters. As a result, it is possible to obtain amplitude characteristics close to those of the filter solved by the Remez algorithm for specifications that change instantaneously from time to time. Finally, a design example is presented to confirm the effectiveness of the present approach.
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