When collecting images, owing to the influence of shooting equipment, shooting environment, and other factors, often low-illumination images with insufficient exposure are obtained. For low-illumination images, it is necessary to improve the contrast. In this paper, a digital color image contrast enhancement method based on luminance weight adjustment is proposed. This method improves the contrast of the image and maintains the detail and nature of the image. In the proposed method, the illumination of the histogram equalization image and the adaptive gamma correction with weighted distribution image are adjusted by the luminance weight of w1 to obtain a detailed image of the bright areas. Thereafter, the suppressed multi-scale retinex (MSR) is used to process the input image and obtain a detailed image of the dark areas. Finally, the luminance weight w2 is used to adjust the illumination component of the detailed images of the bright and dark areas, respectively, to obtain the output image. The experimental results show that the proposed method can enhance the details of the input image and avoid excessive enhancement of contrast, which maintains the naturalness of the input image well. Furthermore, we used the discrete entropy and lightness order error function to perform a numerical evaluation to verify the effectiveness of the proposed method.

Gamma correction is an essential function and is time consuming task in every display device such as CRT and LCD. And gray scale CCT reproduction in most LCD are quite different from those of standard CRT. An automated fast and accurate display adjusment method and system for gamma correction and for constant gray scale CCT calibration of mobile phone LCD is presented in this paper. We develop the test pattern disply and register control program in mobile phone and devleop automatic measure program in computer using spectroradimeter. The proposed system is maintain given gamma values and CCT values accuratly. In addition, This system is possible to fast mobile phone LCD adjusment within one hour.

Color reproductions in most LCD are quite different from those of standard CRT (cathode ray tube) monitor display because of the nonlinear characteristic in subtractive color reproduction. Moreover, gray scale CCT (correlated color temperature) reproductions in a typical mobile phone LCD depend on the input RGB levels. A simple LUT (Look-up table) method for constant gray scale CCT and gamma characteristic of mobile phone LCD is presented in this paper. We investigate the mobile phone LCD's characteristic of compensation of CCT with using the LUT. LCD's CCT is maintaining about 7500 K, which is the target CCT of mobile phone LCD in this paper. Also LCD's gamma is similar to target gamma.

The gamma correction for the CMOS image sensors are implemented by the method of piecewise linear approximation through a look-up table. In this paper, we propose a quantitative criterion to select the piece linear segment with the same output interval for the reduction of the error between the value of piece linear approximation and gamma correction. After the gamma correction is implemented, the average error occurred by implementing color interpolation in each segment is a basis for the optimum selecting of the piece linear segment of the gamma correction for the CMOS image sensors.

A new multi-luminance-level subfield method is proposed to reduce the low gray-level contour of an alternate current plasma display panel (AC-PDP). The minimum or maximum luminance level per sustain-cycle can be altered by simultaneously applying the proper auxiliary short pulses. As a result, the multi-luminance levels per one or two sustain pulse pairs can be expressed by properly adjusting the auxiliary short pulses for the one or two sustain-cycle subfields, thereby suppressing a low gray-level contour of AC-PDP.