Abstract: By combining a plurality of encoding methods actively, an encoding efficiency is enhanced. The first encoder encodes a result of determination whether a prediction error is zero or not. The second encoder encodes the prediction error unless the prediction error is zero. The third encoder encodes the prediction error regardless of whether the prediction error is zero or not. The mode determinator determines the encoding mode, and the encoding controller selectively operates the first encoder, the second encoder, and the third encoder according to the encoding mode determined.

Abstract: In an image enhancement method and a circuit therefor, a luminance signal is extracted from input color signals. The luminance signal, extracted in screen units, is divided into subimages according to the mean value of the luminance signal. The gray level histograms of the divided subimages are independently equalized, and an adjusted luminance signal is output. The color signals are varied on the basis of the adjusted luminance signal, and compensated color signals are output. Accordingly, an abrupt variation in brightness and an artifact are effectively reduced, image contrast is enhanced, and an undistorted color signal is provided at the same time. Also, in order to reduce the hardware of the circuit, an input luminance image is quantized, the quantized image is divided into a predetermined number of quantized subimages on the basis of the mean of the quantized image, and an independent histogram equalization is performed on each of the quantized subimages.

Abstract: An image compression scheme is disclosed which models the human visual perception system. Using quantization of image error values, according to a visually-lossless scheme, an image can be compressed such that it is visually indistinguishable to the naked eye from the original image. To aid in image compression on portable devices such as a digital camera, the quantization can be precoupled into a look-up table.