Abstract: An image rendering system, for generating discrete tone image data representing a continuous-tone image for rendering by a rendering device, the image rendering system includes a stochastic threshold array generating arrangement and an image data processing section. The stochastic threshold array generating arrangement generates a plurality of stochastic threshold arrays from a random seed pattern that have been subsequently optimized to reduce image artifacts in the rendering of tones. Each pattern is optimized to reflect (i) a selected trade-off between grain and possible mottle in the rendered image, (ii) distortions introduced by the rendering device in rendering an image defined by the pattern and an observer in viewing the image, and (iii) boundary effects so that the patterns, when tiled together, have optimal visual characteristics proximate their respective edges.

Abstract: A method and apparatus for image-dependent color saturation correction in natural scene images in electronic documents is provided, wherein an input image is converted from its original color space definition to a luminance-hue-saturation color space, such as HSV space, where S has a strong correlation to perceived saturation. That saturation component of the signal is averaged over the image for at least a region of its input value range corresponding to brightness, and the determined average is compared to a threshold selected to represent desirable saturation level. If saturation is less than target saturation, a filtering function is selected, operable on the image to enhance saturation as a function of the average saturation and desired saturations. Otherwise, no change is made to the image.

Abstract: A digital color image quantization mechanism employs sequential product code vector quantization, to sequentially extract chrominance and luminance values from the vectors and quantizes chrominance and luminance features in accordance with an asymptotically optimal quantizer density function of the color space histogram along respective chrominance and luminance axes into a plurality of luminance-chrominance sub-regions or color space cells, such that each partitioned color cell is associated with a color of the output palette through which the color composition of a reproduced color image is defined. A map of chrominance and luminance output codes is generated for the respective pixels of the output color image in accordance with the axial splitting or quantization of the chrominance and luminance components of the histogram.