Abstract: Methods and apparatus for spectrally-encoding plural source images and for providing the spectrally-encoded plural source images in a composite image, for rendering the composite image in a physical form, or for recovering a normalized version of an encoded source image from the rendered composite image such that the recovered source image is made distinguishable as a normalized color image.

Abstract: Methods and apparatus for spectrally-encoding plural source images and for providing the spectrally-encoded plural source images in a composite image, for rendering the composite image in a physical form, or for recovering at least one of the encoded source images from the rendered composite image such that the recovered source image is made distinguishable. Source image confusion in a rendered composite image is controlled by application of a illuminant-neutral gray component replacement (GCR) technique to the darkness common to the different colorants under the multiple illuminants.

Abstract: Selective edge softening and selective edge dithering is introduced into an image representation to improve local control where halo problems are expected. Selective areas of dilation are isolated and separately dithered or halftoned, the result of which is then swapped back into or substituted for the stored original image. In this manner misregistration and color plane-to-plane interactions can be compensated for in plural image forming station architecture systems. The same technique is also valuable in monochrome systems as an aid to overcoming edge displacement and slow toner problems when the selective edge softening is selectively applied to edges which are in particular perpendicular to the fast scan direction.

Abstract: What is disclosed is a method for digital watermarking in a calibrated printing path and comprises: first receiving a pixel possessing color values from an input image; receiving a plurality of information bits to be encoded at a corresponding pixel in an output image. Then, one of at least two different GCR functions are selected where the selection is based on the state of the received information bits. The number of GCR functions to be selected from is dependent on the number of possible states of the information bits intended to be encoded at each image pixel and preferably equals the number of states of the information bits intended to be encoded at each image pixel such that the GCR spatially varies across the output image. Further, at least two GCR functions are optimized to carry information and information bits intended to be encoded within the output image are represented with a tag. CMYK values are then generated using the selected GCR function and the color values.

Abstract: What is disclosed is a decoding method for retrieving information bits encoded in a printed image comprising the steps of first receiving an input electronic image as a scanned version of the printed image. A region of interest in the image is then extracted and, for that region, an amount of K colorant present, denoted KH; is obtained. Further, a color value is generated therefrom and the GCR used for encoding that region is determined using KH and the obtained color value. Encoded information bits are retrieved therefrom based on the determined GCR. The estimated KH is preferably evaluated conditional to a capacity signal KL and a luminance signal L. From the obtained data, values of KH, KL, and L, are derived wherein KH is estimated from a high resolution scan, and KL and L are estimated from a down-scaled image, respectively. The capacity signal KL and the luminance signal L are derived from the obtained color value.