Abstract: A method for modifying an input image having an (x,y) array of input pixels, each pixel having an input colorant amount for one or more color channels to form an output image with output colorant amounts, said output image being suitable for printing on a digital printing device having two or more printing levels, including determining an average total pixel colorant amount in a neighborhood of an input pixel in the input image; determining a colorant reduction amount for each color channel of the input pixel responsive to the input colorant amount, the average total pixel colorant amount, and a threshold colorant amount; determining an output colorant amount for each color channel of the input pixel responsive to the colorant reduction amount, the input colorant amount, and a spatially periodic dither signal, so that the average output colorant amount in a neighborhood of each pixel in the output image is constrained to be less than the threshold colorant amount; and repeating steps a) through c) for each pi

Abstract: A method for representing a digital image having color values with an extended color gamut in a storage color space having a limited color gamut including providing a color adjustment function; adjusting the color values of the extended color gamut digital image to fit within the limited color gamut to form a limited color gamut digital image using the color adjustment function; representing the limited color gamut digital image in the storage color space; and associating information about the color adjustment function with the limited color gamut digital image in the storage color space such that the associated information and the limited color gamut digital image are adapted to produce a reconstructed extended color gamut digital image.

Abstract: A method for reproducing digital images having at least one color channel containing pixels using a digital printer having a set of colorants is disclosed. Two or more of the colorants of the set have substantially the same color but different densities. Printer code values for a particular color channel are used to control colorant amounts for the two or more colorants.

Abstract: A method for representing a digital image having color values with an extended color gamut in a storage color space having a limited color gamut comprising the steps of: adjusting the color values of the extended color gamut digital image to fit within the limited color gamut to form a limited color gamut digital image; representing the limited color gamut digital image in the storage color space; determining a clipped limited color gamut digital image in which highly quantized regions in the limited color gamut digital image have been clipped; determining a residual image representing a difference between the extended color gamut digital image and the clipped limited color gamut digital image; and associating the residual image with the limited color gamut digital image in the storage color space such that the associated residual image and the limited color gamut digital image in the storage color space are adapted to be used to form a reconstructed extended color gamut digital image.

Abstract: A method for modifying a digital image having color values with an extended color gamut comprising the steps of representing the extended color gamut digital image with a limited color gamut digital image and one or more associated residual image(s) representing a difference between the extended color gamut digital image and the limited color gamut digital image; specifying one or more desired image modification(s) to be applied to the extended color gamut digital image; and modifying the limited color gamut digital image and the residual image(s) to form a modified limited color gamut digital image and one or more modified residual image(s) in response to the specified desired image modification(s).

Abstract: A method for representing a digital image having color values with an extended color gamut in a storage color space having a limited color gamut includes adjusting the color values of the extended color gamut digital image to fit within the limited color gamut to form a limited color gamut digital image; representing the limited color gamut digital image in the storage color space; determining a set of residual images representing a difference between the extended color gamut digital image and the limited color gamut digital image; and associating the set of residual images with the limited color gamut digital image in the storage color space such that the associated residual images and the limited color gamut digital image is adapted to be used to form a reconstructed extended color gamut digital image.

Abstract: A digital image processing system includes one or more opto-electronic image digitization device(s) which digitize still photographic images and produce an extended color gamut digital image corresponding to each still photographic image, and an image processing unit, coupled with said image digitization device(s), which is operative to receive a plurality of extended color gamut digital images from the image digitization device(s).

Abstract: A method for representing a digital image having color values with an extended color gamut in a storage color space having a limited color gamut includes adjusting the color values of the extended color gamut digital image to fit within the limited color gamut to form a limited color gamut digital image; representing the limited color gamut digital image in the storage color space; determining a residual image representing a difference between the extended color gamut digital image and the limited color gamut digital image; and associating the residual image with the limited color gamut digital image in the storage color space such that the associated residual image and the limited color gamut digital image in the storage color space are adapted to be used to form a reconstructed extended color gamut digital image.

Abstract: A new multitoning technique is proposed that combines error diffusion, blue-noise dithering and over-modulation in an adaptive algorithm to achieve high quality multilevel printing with smooth texture transition. A periodic dither signal is first added to an input digital image wherein the amplitude of the periodic dither signal is a function of the input pixel value for each input pixel. The amplitude of the periodic dither signal is larger for input pixel values near the N output levels, and the amplitude of the periodic dither signal is smaller for input pixel values intermediate to the N output levels to produce a modified input image. Then, a multi-level error diffusion halftoning algorithm is applied to the modified input image wherein the error diffusion halftoning algorithm uses a set of error feedback weights which are adjusted according to the original input pixel value for each input pixel.

Abstract: A scene balance correction method for a digital imaging device, including the steps of determining a low-resolution image from an input image in an input color space; applying a color transformation to convert the low-resolution image to a standard color space to form a standard color space low-resolution image; analyzing the standard color space low-resolution image to determine a set of standard color space scene balance correction factors; determining a set of corresponding input color space scene balance correction factors from the standard color space scene balance correction factors using the color transformation; and applying the corresponding input color space scene balance correction factors to the input image to form a corrected input image.

Abstract: A method for characterizing a response function of an output device, the method comprises the steps of producing a test image on the output device with a set of one or more test patches having known code values; obtaining one or more captured images of the test image using a digital camera; determining colorimetric values for each of the test patches in the captured images using a known response function of the digital camera; and determining a response function of the output device which relates the known code values to the determined colorimetric values.

Abstract: A method for segmenting a digital image into a foreground region and a key color region including characterizing a distribution of key color values; using the distribution of key color values to produce a multi-dimensional look-up-table having three or more dimensions indexed by color values in a selected color space to define a key color volume; addressing the multi-dimensional look-up table with color values of pixels in the digital image to determine whether the color values of such pixels are within the key color volume; and labeling pixels in the digital image whose color values fall within the key color volume to be within the key color region and labeling all other pixels to be within the foreground region whereby the digital image is segmented into the foreground region and the key color region.

Abstract: A method is disclosed for calibrating a digital printer to provide a substantially aim printer response. A test target is processed through a set of potential calibration functions to form a set of processed test targets and the set of processed test targets is printed using the digital printer. Thereafter, the printer response for each of the potential calibration functions is evaluated by visually examining the printed set of processed test targets. The potential calibration function that best matches a visual criterion is then selected.

Abstract: A method for determining a control signal for use in combining a first digital image that includes both a foreground region and a key color region having an associated key color with a second background digital image, both images including pixels having color values is disclosed. The method includes segmenting the first digital image into a foreground region and a key color region; and identifying transition region pixels in the first digital image that are in the vicinity of a boundary between the segmented foreground region and the segmented key color region. The method further includes computing a color difference signal between the color values of the first digital image and the key color for at least some pixels in the transition region; and computing a control signal for transition region pixels as a function of the color difference signal, where the control signal is to be used to combine the foreground region of the first digital image with the second background digital image.

Abstract: A method for processing a digitized continuous tone image so that such processed image is adapted to be applied to an image rendering device which prints dots from a set of two or more possible dot-areas and from a set of colorants having different colorant concentrations is disclosed. The method includes selecting a set of N dot-area and colorant concentration combinations, each of said combinations producing a different integrated optical density value and multilevel halftone processing the digitized continuous tone image to produce an output image having a set of output levels wherein one member of the set of N dot-area and colorant concentration combinations is associated with each of the possible output levels.

Abstract: A method and apparatus are disclosed for calibrating a digital printer to provide a substantially aim printer response. A test target is processed through a set of potential calibration functions to form a set of processed test targets and the set of processed test targets is printed using the digital printer. Thereafter, the set of printed test targets is measured to determine the printer response. An error criterion is determined for each measured test target by comparing the measured printer response for each of the set of potential calibration functions to the aim printer response. The calibration function which has the smallest value of the error criterion is then selected.

Abstract: A method for transforming input color values to device control signals for a color printing device having an output response that is approximately invariant for ranges of the device control signals near the maximum or minimum allowable device control signals, wherein the input color values are transformed into the device control signals that are to be used to reproduce the input color values is disclosed.

Abstract: A method for halftoning a digital image having an x,y array of pixels each having an associated input pixel value, includes the steps of providing a memory containing a dither bitmap for each input pixel value of the digital image where the dither bitmaps are partially correlated; selecting a dither bitmap corresponding to the input pixel value for a pixel in said digital image; modularly addressing the selected dither bitmap with the location of said pixel to obtain an output halftone image value; and repeating steps for each pixel in the digital image.

Abstract: A method for combining a first digital image and a second background digital image, both images including pixels having color values, wherein the first digital image includes both a foreground region having foreground color values and a key color region characterized by a key color, as well as a mixed region where the pixel color values are a mixture of the foreground color value and the key color, includes determining a first control signal that indicates the relative proportions of the foreground color value and the key color for pixels in the first digital image; and segmenting the first digital image into a key color region and a non-key color region in which the non-key color region includes pixels in the first digital image that are not in the key color region.

Abstract: An arrangment is disclosed for reducing edge artifacts produced when printing a digital image on a digital printer, which printer is capable of producing multiple output levels, said digital image being represented as a rectangular array of pixels. In this arrangement, the following steps are accomplished by: computing difference signals between a center pixel value and pixel values of a set of one or more neighboring pixels; determining a pixel correction value responsive to the computed difference signals; and computing a new center pixel value by modifying the center pixel value using the pixel correction value.