Abstract:
A method for halftoning a multi-channel digital color image having an x,y array of color pixel values, wherein at least two color channels are similar having substantially the same color but with low- and high-densities, includes the steps of: providing a matrix of dither values for each group of similar color channels wherein two or more of the matrices of dither values are designed jointly to minimize a visual cos t function; for at least one group of similar color channels, forming an inverted matrix of dither values by subtracting the value of each element of the matrix of dither values for that group from a predetermined maximum value, associating the inverted matrix of dither values with one of the low- or high-density color channels, and associating the matrix of dither values for that group with the other low- or high-density color channel of that group; for each color channel of the multi-channel digital color image modularly addressing the matrix of dither values associated with that color channel using the location of a pixel in the digital color image to obtain ad addressed dither value; using the addressed dither value for each color channel, together with the pixel value for the corresponding color channel, to determine an output halftone image value for each color channel.
Abstract:
An image capture system includes a sparsely sampled extended dynamic range image sensing device having fast photosites interspersed with slow photosites for producing a sparsely sampled high resolution digital image having fast pixel values produced by the fast photosites and slow pixel values produced by the slow photosites. A processor employs the slow pixel values to expand the dynamic range of the fast pixel values in the sparsely sample high resolution digital image to form a full resolution digital image having an extended dynamic range. A color encoder reduces the dynamic range of the full resolution digital image to fit within the dynamic range of a storage color space having a dynamic range less than that of the full resolution digital image to form a limited dynamic range digital image represented in the storage color space.
Abstract:
A method for processing an extended color gamut digital image so as to represent the extended color gamut digital image in a storage color space having a limited color gamut digital image and for paying for such processed digital image including a user sending or authorizing the sending of an extended color gamut digital image to a processing site where the extended color gamut digital image is to be processed. Processing such extended color gamut digital image at the processing site can be accomplished by 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, and representing the limited color gamut digital image in the storage color space. Further, by determining one of more residual images representing differences between the extended color gamut digital image and the limited color gamut digital image, and associating the one of or more residual image(s) with the limited color gamut digital image in the storage color space such that the associated residual image(s) and the limited color gamut digital image are adapted to be used to form a reconstructed extended color gamut digital image. The method also includes the user making payment, and making the processed extended color gamut digital image available to the user via a communications network.
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 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 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:
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.
Abstract:
An improved error diffusion method for producing an output image from an input image having a set of digitized continuous-tone pixels is disclosed. The method includes computing a visually perceived input value for a digitized continuous-tone input pixel and computing a visually perceived output value for each of the possible output levels. The method further includes selecting the output level in response to the visually perceived input values and the visually perceived output value for each of the possible output levels according to an error criterion; determining an error signal between the visually perceived input value and the visually perceived output value for the selected output level; and weighting the error signal and adjusting the computed visually perceived input values for nearby pixels which have not been processed.
Abstract:
This invention minimizes the visibility of quantization artifacts associated with multi-dimensional color-calibration look-up tables of a limited size. Such artifacts occur when it is not practical to use interpolation methods to approximate color values which are intermediate to the color values stored in the look-up table. In such cases the input color signals are simply quantized for the purpose of addressing the look-up table. This invention works by applying local mean preserving spatial modulation to the input color image values prior to the quantization step. As with multi-level halftoning techniques, the result is that the appearance of intermediate color values is created because the observer will spatially average the output color values.