This paper proposes a retinex theory-based approach to RGB-to-RGBW conversion that preserves the human color perception within a pre-determined level of color distortion for RGBW displays. The proposed method primarily consists of two procedures. In the first, it searches for the maximum intensity level that induces no color distortion for a given image by extracting the white spectra from the common components of the RGB primary colors and adjusting all the pixels' gains uniformly. In the second, the proposed method applies an additional gain to each pixel based on its chromaticness and controls the color distortions arising from the individual gains using the color perception estimated by retinex theory and a feedback mechanism. Experimental results showed that the proposed method was more effective than conventional methods in terms of intensity increment and color preservation. For Kodak test images, the proposed method increased the average intensity by 1.4987 times with a color-distortion level of 0.0094 compared to reference RGB displays, whereas the conventional methods increased the average intensity by 0.8624–1.3429 times with color-distortion levels of 0.0325–0.0682. The surplus intensity yielded by the proposed method can be used to dynamically reduce the power consumption of a liquid crystal display (LCD) backlight or to provide brighter images on LCDs.
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