Abstract: New interpolation techniques allow improved efficiency and speed in performing color space conversions. A radial interpolation technique accomplishes an interpolation by generating successive sub-cubes. A value of a vertex of the final sub-cube generated is used as the result of the interpolation. Subcubes are generated by averaging a selected vertex value with the vertex values of each of the remaining vertices. A pruned radial interpolation technique employs a subset of the vertex values of the initially selected cube to generate the result of the interpolation, thereby improving upon the efficiency of the radial interpolation. A tetrahedral interpolation technique accomplishes an interpolation by generating successive subcubes. A value of a vertex of the final sub-cube generated is used as the result of the interpolation. Subcubes are generated by applying a mathematical relationship which allows computation of sub-cube vertex values through a series of logical AND, logical OR and averaging operations.

Abstract: A variable resolution color scanner comprising multiple color line sensors arranged substantially in parallel and at a mutual distance. The scanner is capable of providing color components that are combined by means of delays and interpolators in order to form a high precision color representation of a scanned original. The color components are combined electronically such that at least one of the color components represent(s) an actually imaged line on the original, and such that the other color components represent estimated lines. Alternatively, the color components are combined electronically such that all other color components represent estimated lines.

Abstract: New interpolation techniques allow improved efficiency and speed in performing color space conversions. A radial interpolation technique accomplishes an interpolation by generating successive subcubes. A value of a vertex of the final subcube generated is used as the result of the interpolation. Subcubes are generated by averaging a selected vertex value with the vertex values of each of the remaining vertices. A pruned radial interpolation technique employs a subset of the vertex values of the initially selected cube to generate the result of the interpolation, thereby improving upon the efficiency of the radial interpolation. A tetrahedral interpolation technique accomplishes an interpolation by generating successive subcubes. A value of a vertex of the final subcube generated is used as the result of the interpolation. Subcubes are generated by applying a mathematical relationship which allows computation of subcube vertex values through a series of logical AND, logical OR and averaging operations.

Abstract: A summing interpolation method is provided for transferring images between coordinate systems in an affine transformation, using a simplified series of interpolation formulas. The small number of interpolation formulas required by the present invention permits the calculation of an interpolated pixel value through the addition of pixels with discrete locations bordering a calculated, non-discrete, pixel location. The data of discrete pixel locations closer to the calculated location are added more often in the interpolation than those further away. Specifically, the non-integer remainder of the calculated location is rounded off to one-quarter increments in the X and Y axis, and an interpolation formula is chosen in response to the rounded increment location values. In this manner, all possible calculated locations are interpolated with a small number of fixed interpolation formulas. A interpolation summing system, for use in an affine transformation, is also provided.

Abstract: New interpolation techniques allow improved efficiency and speed in performing color space conversions. A radial interpolation technique accomplishes an interpolation by generating successive sub-cubes. A value of a vertex of the final sub-cube generated is used as the result of the interpolation. Sub-cubes are generated by averaging a selected vertex value with the vertex values of each of the remaining vertices. A pruned radial interpolation technique employs a subset of the vertex values of the initially selected cube to generate the result of the interpolation, thereby improving upon the efficiency of the radial interpolation. A tetrahedral interpolation technique accomplishes an interpolation by generating successive sub-cubes. A value of a vertex of the final sub-cube generated is used as the result of the interpolation. Sub-cubes are generated by applying a mathematical relationship which allows computation of sub-cube vertex values through a series of logical AND, logical OR and averaging operations.

Abstract: A method for color error diffusion using semi-vector quantization is proposed that simplifies error diffusion calculations. When three color separations are used, the two separations with the most visually perceptive color output are compared with one another to determine their output colors, while the third, least visually perceptive separation, is treated separately. A correction term may be applied to the third separation based on the color output of the first two separations to insure uniformity of ink coverage. This method yields results close to vector quantization and also minimizes fluctuation in the two most visually perceptive output colors. Of course, this method may be used with more than three color separations. For example, when four color separations are used, the least visually perceptive color is processed differently than the three other color separations.

Abstract: In a method for modifying the resolution of an image obtained by digitising a real image, the digitised image includes a plurality of pixels of a particular intensity. The outlines in the digitised image are studied and isolated and additional pixels are created by interpolation of the intensities of original pixels located on one side of an outline to form an image with a modified resolution. The studying of outlines is achieved by locating, for close pixels, the intensity transitions representative of a gradient exceeding a particular threshold. The method is utilized for modifying the image resolution of facsimile machines.

Abstract: An improved interpolation method in which a threshold value used for determining a pixel value of a pixel generated by interpolation according to a context which is a state value of adjacent pixels. In the interpolation method, the ambiguity between the interpolation value and the threshold value is removed by using the context, thereby reducing the blocking and smoothing phenomena in the restored binary image.

Abstract: An improved interpolation method in which a threshold value used for determining a pixel value of a pixel generated by interpolation according to a context which is a state value of adjacent pixels. In the interpolation method, the ambiguity between the interpolation value and the threshold value is removed by using the context, thereby reducing the blocking and smoothing phenomena in the restored binary image.

Abstract: The present invention is a method and apparatus for computing color transformations of source images. It performs color transformations using a lookup table and a hashing block for referencing entries in the lookup table. The index generated by the hashing block is dependent on a first color value. A color encoding block is coupled to the lookup table for generating an encoded color value dependent on the first color value. The index produced by the hashing block is further dependent upon response characteristics of the human eye. The hashing block generates indexes referencing widely separated entries in the plurality of entries of the lookup table when first color values have small differences in value. A comparing block is coupled to the lookup table and the color encoding block for comparing the entry of the lookup table and the encoded color value to determine a match. A color calculation block is coupled to the lookup table for generating a second color value dependent on the first color value.

Abstract: A system (1) for enhancing the resolution of a video image by a predetermined enhancement factor is provided. System (1) generally includes an interpolation subsystem (10), a data storage module (20), and a pixel insert positioning module (30). Included within interpolation subsystem (10) are a classification module (100), a bilinear interpolation module (200), and an adaptive interpolation module (300). Classification module (100) receives the original image pixels in a specified field of the given video image and designates for each original image pixels it receives one of a plurality of predefined classifications. Based upon this classification, one of the bilinear interpolation (200) and adaptive interpolation (300) modules is selected for actuation in generating the supplementary image pixels necessary to support resolution enhancement.

Abstract: In a digital printing apparatus in which primary colorants are selected by an error-diffusion process, a method takes into account situations in which a colorant is selectable from within the gamut defined by certain other primary colorants. In the case of a printer in which, in addition to CMYK colorants, a mid-gray colorant is also selectable, the method avoids the problem in which an error-diffusion algorithm mandates the simulation of colors outside the gamut.

Abstract: The method of the invention provides an improved method for converting primary printer color values to combinations of the primary printer color values and black to achieve improved printer output color representations. The method includes the following steps. A first balanced set of primary printer color combinations (e.g., CMY) is initially derived which provides a balanced gray representation at various levels of primary color concentration. A second balanced set of primary printer color combinations (e.g., CMYK) is derived which provides a balanced gray representation at various levels of color concentration. Next, a set of primary printer colors (CMY) with K is derived, using the first balanced set, which best represents shadow colors, and a maximum color value is chosen therefrom. Then, a similar set of primary printer colors is calculated which best represents highlight values, by interpolating from the chosen maximum color value to a white value.

Abstract: New interpolation techniques allow improved efficiency and speed in performing color space conversions. A radial interpolation technique accomplishes an interpolation by generating successive subcubes. A value of a vertex of the final subcube generated is used as the result of the interpolation. Subcubes are generated by averaging a selected vertex value with the vertex values of each of the remaining vertices. A pruned radial interpolation technique employs a subset of the vertex values of the initially selected cube to generate the result of the interpolation, thereby improving upon the efficiency of the radial interpolation. A tetrahedral interpolation technique accomplishes an interpolation by generating successive subcubes. A value of a vertex of the final subcube generated is used as the result of the interpolation. Subcubes are generated by applying a mathmatical relationship which allows computation of subcube vertex values through a series of logical AND, logical OR and averaging operations.

Abstract: A judgment is made as to whether an interpolation point in an original image is or is not located at an image edge portion. The judgment is made by using a threshold value having been set such that, as a desired level of sharpness of an interpolation image obtained from interpolation processing becomes low, the threshold value may become large. When an interpolation point is judged as being located at an image edge portion, an interpolated image signal component corresponding to the interpolation point is calculated with interpolation processing capable of keeping the image edge portion sharp.

Abstract: A method and apparatus for achieving an ultra-small or compressed image buffer images at half the resolution and then scales by two to achieve the device resolution. Acceptable quality can be maintained by identifying edge and interior portions of the page image and using this information to scale intelligently. A split-level frame buffer provides this identification of the image components. Further, an extension of block-truncation coding can be used with the split-level frame buffer to provide up to a 16 to 1 compression for an overall compression of up to 64 to 1. Actual techniques to scale these encodings are described along with new encodings for graphics and text designed this high compression of the image.

Abstract: An N-dimensional correction space is constructed with weighting coefficients .xi. and .eta. that are used for determining reflection coefficients for an N-order target color, where the weighting coefficients .xi. and .eta. specify the lengths of the sides constituting the N-dimensional correction space, and where 2.sup.N reference colors are located at the corners of the N-dimensional correction space. The N-dimensional correction space is divided by N pieces of (N-1)-dimensional spaces that run through the target color, into 2.sup.N partial N-order correction spaces. The reflection coefficient for the target color is determined by multiplying a reference reflection coefficient with respect to each of the 2.sup.N reference colors by the volume of a partial N-dimensional correction space that is located at a diagonal position against a coordinate point of each reference color and summing up the results of multiplication for the 2.sup.N reference colors.

Abstract: An illuminance spectrum I of reflected light from a color print of an arbitrary dot percent d is defined by a diffuse reflection coefficient Sb(d,.lambda.) and a specular reflection coefficient Ss(d,.lambda.). The diffuse reflection coefficient Sb(d,.lambda.) is determined by linear interpolation of a plurality of reference reflection coefficients Sb(d.sub.i,.lambda.) for a plurality of reference dot percents d.sub.i. The specular reflection coefficient Ss(d,.lambda.) is also determined by linear interpolation of a plurality of reference reflection coefficients Ss(d.sub.j,.lambda.) for a plurality of reference dot percents d.sub.j. The illuminance spectrum of reflected light is then determined according to these reflection coefficients Sb(d,.lambda.) and Ss(d,.lambda.). Color data representing the colors of the print in a calorimetric system suitable for an output device are subsequently generated from the illuminance spectrum.

Abstract: A color image processing apparatus of the present invention includes (1) first lattice for dividing a color separation signal space in the form of a lattice so as to store in a table coordinates of lattice points of the color separation signal space thus divided and (2) second lattice for further dividing a specific unit cube of the lattice in the form of a lattice so as to additionally store in the table coordinates of lattice points of the specific unit cube thus divided. Depending on whether or not inputted image data of image information belong to the specific unit cube of the lattice, color correction method having different conversion accuracy is adopted, thereby permitting to provide a color image processing apparatus which reduce the occurrence of an error when color-correcting a color requiring accurate color correction, and prevent the continuity of an image from being not kept.

Abstract: To perform processing to increase the number of pixels of inputted image data, the inputted image data having low resolution is converted to image data having high resolution. For this conversion, one pixel of the low resolution data is interpolated, a difference value between a predetermined value and image data included in an interpolating-pixel block which corresponds to a pixel of interest of the low resolution data, is calculated, and pixel values of pixels in the interpolation-pixel block are determined in accordance with the difference value. Furthermore, multi-level image data on which pixel values have been determined is binarized by the dither method, to determine pixel values such that the smaller the absolute value of the difference value is, the larger the difference from the predetermined value.

Abstract: An original image signal, which represents an original image and is made up of a series of original image signal components Yij, is obtained. Corresponding interpolation coefficients Bij and Cij, which are set for each of the original image signal components Yij, in two different interpolating functions f and g, represented by Formulas (1) and (2), for obtaining two interpolation images having different levels of sharpness are linearly combined with each other by using Formula (3). A new interpolation coefficient Aij is thereby obtained. An interpolating operation is carried out on the original image signal components Yij with an interpolating function h, which has the new interpolation coefficient Aij and is represented by Formula (4). An interpolation image signal is thereby obtained, which is made up of a series of image signal components occurring at intervals different from those of the original image signal components Yij,f=.SIGMA.Bij.multidot.Yij (1)g=.SIGMA.Cij.multidot.Yij (2)Aij=(1-.alpha.)Bij+.

Abstract: Color image decoding is achieved by a simplified method of decoding a spatially and chromatically multiplexing image plane (32), such as a plane consisting of RGB (Red-Green-Blue) pixels (22) by performing a summation of pixels of all three colors in a neighborhood of a missing pixel. The decoding process has applications in decoding images made by a data processor, made by an imaging device with a mosaic color filter, or made by a multi-sensor CCD imaging device with a sensor offset (800). Various techniques of entropy reduction, smoothing and speckle reduction may be incorporated into the coefficient pattern. The coefficient pattern may be generated automatically using a process of correlated decoding and may be adjusted by hand using a process of trial and error.

Abstract: A simplified arithmetic expression is used deed upon a divided segment in an interpolating solid body to be used for an interpolating operation, where an objective point for interpolation is located, for example on a grid point, on a line or on a plane, the number of times of making reference to a table or performing an arithmetic operation, such as addition, subtraction, multiplication and division is reduced to realize a high speed interpolating operation.

Abstract: An input color signal is converted into a color signal representing a color which is visually closer to a color represented by the input color signal by performing gamut mapping processing based on the visual characteristics of humans. An image processing method includes the steps of inputting color signals, and performing gamut mapping processing in which the input color signal is converted into a color signal having a hue different from the hue of the input color signal based on a locus set corresponding to the hue and color saturation of the input color signal in color space.

Abstract: A system for processing images includes an image file subsystem providing a source signal representing an input image; a color transformation subsystem coupled to the image file subsystem and accepting as input the source signal and producing a target signal therefrom, and an image forming subsystem coupled to the color transformation subsystem and forming a physical manifestation of the input image in response to the target signal, the color transformation subsystem being configured to establish a memory "cube" area representative of possible source signals, to define a sub-cube portion of the memory area as representative of the source signal; to determine possible target signals corresponding to the sub-cube portion; and to determine the target signal responsive to the possible target signals. If interpolation is found to be accurate for a mini-cube portion of the sub-cube, truncation or interpolation are used to derive the target signal; otherwise, the target signal is determined directly.

Abstract: A sensor-to-sensor distance correcting method and a circuit therefor in an image reading apparatus having a plurality of line sensors are provided.

Abstract: A colour conversion apparatus maps image data from an input colour space (RGB) to an output colour space (CMYK). A transfer function between the colour spaces is known relevant to an appropriate display medium such as a printer and this is divided into intervals for interpolating between the colour spaces. The intervals vary in length depending on the behavior of the transfer function with the intervals being shorter where the transfer function is not well behaved (i.e. rapid change in slope). Interpolation is performed over each interval based on mapping a volume of input pixel data to a corresponding volume of a component of output pixel data. Interpolation is performed between those points to derive an output pixel colour component value. The process is repeated for each primary colour component of the output colour space to produce composite output pixels. Near-white and near-black colour correction is also performed.

Abstract: A multi-point interpolation apparatus for reading out plural picture data from a picture memory and effecting interpolation includes apparatus that writes luminance data and chroma data of pixel data at (n+1) point pixel positions at the same address of a picture memory, and reads out luminance data and chroma data from the picture memory. The apparatus also selects, from the luminance data and chroma data of the pixel data at the read-out (n+1) point pixel positions, the luminance data and the chroma data at the n-point pixel positions, while generating, from the luminance data and the chroma data at the selected n-point pixel positions, the luminance data and the chroma data at the designated interpolating point by n-point interpolation.

Abstract: A color signal processing apparatus which is capable of providing satisfactory operation accuracy while keeping the memory size relatively small. A dividing circuit divides three input signals R, G, and B into upper bit data and lower bit data. A first table memory stores output values for all combinations of the three upper bit signals, the upper bit data of the three input signals being accepted as address signals and a first output value being provided. A second table memory stores the output values for all combinations of signal values obtained by adding a prescribed offset (e.g. 2.sup.NL /2) to a signal value which is expressed by upper bits, upper bit data of the three input signals being accepted as address signals and a second output value being provided. An interpolation circuit outputs a final output signal in accordance with the output value of the first table memory, the output value of the second table memory and the lower bit data.

Abstract: The invention relates to pixel insertion on optical scanners. The invention increases the efficiency of video buffer in optical scanners and improves the speed of I/O device by locating the position of interpolation device in front of video buffer which is for temporarily storing image data and outputting the image data. Immediately after the video buffer is an input buffer which is for receiving the output of the video buffer. The input buffer provides an interface for video buffer and the interpolation device. The function of the interpolation device is for inserting pixels into the original pixels to increase the resolution of the image. When the host machine is requesting image data, an output buffer delivers the image data in the interpolation device to an I/O device for the host machine to read.

Abstract: An interpolating operation is carried out on original image signal components which make up an original image signal representing an original image and represent values of original picture elements arranged in a grid pattern at predetermined intervals to obtain interpolation image signal components representing values of interpolation picture elements arranged in a grid pattern at intervals different from those of the original picture elements. Each interpolation image signal component is operated by multiplying the image signal components for a plurality of original picture elements adjacent to the interpolation picture element by respective interpolation coefficients calculated from the image signal components for the adjacent original picture elements.

Abstract: A color image processing system in which image data generated in other systems can be commonly used is disclosed. In the color image data processing system, an image processing unit processes color image data represented in a uniform color space system under illumination by a first light source, and the image data includes information relating to the first light source. An image output unit receives color image data represented in a uniform color space system under illumination by a second light source and produces color images according to the color image data. A correction control unit in the image processing unit judges whether or not the first light source coincides with the second light source. A correction formula calculating unit calculates a correction formula corresponding to the difference in characteristics between the first light source and the second light source. A light source difference correction unit corrects the color image data according to the correction formula.

Abstract: An apparatus for generating interpolator input data for a color space conversion from a RGB color space to a CMYK color space includes an address generator having eight outputs and a memory having eight inputs each connected to one of the address generator outputs. The inputs to the address generator are the three sets of four higher order bits, RH, GH, and BH, of the twenty four bit RGB color space value and two bits for selecting one of the dimensions in the CMYK space to which the conversion will be directed. From these inputs, the address generator can generate 19,652 addresses for accessing interpolator input data stored in the memory. The address generator simultaneously generates eight addresses for accessing interpolator input data stored in the memory.

Abstract: An address exchanger and a data exchanger are provided at both sides of a plurality of look-up tables (LUTs). An even number address is constantly accessed at one of the LUTs and an odd number address is constantly accessed in the other LUTs. An interpolating operation on the basis of values output from the respective LUTs may constantly cause the same results as can be obtained without address exchange. By this, for the memory to be accessed by the odd number address and the even number address, a grid point data for other transformation characteristics may be stored. Therefore, in the data transformation apparatus performing data transformation through interpolation employing a plurality of LUTs, memories of respective LUTs can be efficiently used for permitting data transformation of a plurality of kinds of transformation characteristics.

Abstract: A color printer driver for a printer includes a reproduction look-up table (LUT) which stores CMY values for colors both in-gamut and out-of-gamut of the printer. For close-in out-of-gamut colors, the reproduction LUT stores perceptually matched CMY values whereas for far-out-of-gamut colors, the reproduction LUT stores saturation matched CMY values.

Abstract: A printing device (10) is commanded to print a reference set of intensity values from almost white or highlight regions through almost dark or shadow regions. A measuring device (12) measures the actual outputted printer intensity levels from the printing device (10). An interpolator (14) interpolates the printer intensity levels into a best fit smooth curve plotted against the reference set of intensity levels which produces a non-linear function. A mapping means and converter (24a, 24b) calculate a set of fractional intensity values and densities which produce a linear function when mapped with the printer intensity levels. A dot area parameter calculator (28) calculates a set of dot parameters defining a configuration of a halftone dot required to fill an area within the halftone cell corresponding to each intensity level. For each position of each halftone cell, a measurement processor (30) determines a distance between a current scan position (a,b) and a nearest edge defined by the dot parameters.

Abstract: A method and device for multidimensional data transformation is disclosed. A multidimensional, non-linear data memory storage construct provides simultaneous access to data in all dimensions without duplication of memory. For "n" dimensions, 2.sup.n locations describe the smallest subarea location in the multidimensional construct. Therefore, 2.sup.n memory banks are provided in which to store corresponding interpolation data. By recognizing that boundary points of the n-dimensions are common, duplication of memory is avoided by providing an addressing and sorting mechanism which allows interpolation of stored data correlated to the input data.

Abstract: Disclosed is a technique for N-dimensional image data interpolation processing utilizing a multi-stage technique. Each stage processes one of the N-dimensions to constrain output data in that dimension. Subsequent processing in successive stages only occurs within the confines of the constrained output of the previous stage. Multiple data values can be simultaneously processed in the different stages, to pipeline the interpolation process.

Abstract: The present invention is a method and apparatus for transforming source images to output images. It performs color transformations using a lookup table and a hashing circuit for referencing entries in the lookup table. The index generated by the hashing circuit is dependent on a first color value. A color encoding circuit is coupled to the lookup table for generating an encoded color value dependent on the first color value. The index produced by the hashing circuit is further dependent upon response characteristics of the human eye. The hashing circuit generates indexes referencing widely separated entries in the plurality of entries of the lookup table when first color values have small differences in value. A comparing circuit is coupled to the lookup table and the color encoding circuit for comparing the entry of the lookup table and the encoded color value to determine a match.

Abstract: An apparatus for routing interpolator input data for a color space conversion from a RGB color space to a CMYK color space includes a selective two's complementer coupled to a hardware interpolator. The inputs to the selective two's complementer include three sets of four lower order bits, RL, GL, and BL of a twenty four bit RGB color space value and three least significant bits of three sets of four higher order bits, RH, GH, and BH. The inputs to the hardware interpolator include three outputs from the selective two's complementer and eight inputs for receiving interpolator input data from eight memory banks. The interpolation process can be regarded as determining a location within a cube of a cubic lattice formed from vertices represented by the interpolator input data values.

Abstract: A color correction apparatus includes a preprocessor for generating a minimum value signal, a set of difference signals, and a selecting signal in accordance with values of input XYZ color data, the minimum value signal indicating a minimum value among the input XYZ color values, the difference signals indicating differences between the minimum value and the remaining values of the input XYZ color data, and the selecting signal being used to select one of unit triangular prisms in XYZ color space, a first part for computing a first signal of output color data through interpolation being performed, using predetermined values of output colors corresponding to lattice points of the selected unit triangular prism, in accordance with a value of the minimum value signal and in accordance with values of the difference signals, a second part for computing a second signal of the output color data in accordance with the value of the minimum value signal, and a third part for generating a third signal indicating the out

Abstract: An uneven dividing unit unevenly divides an input gamut into divisions which have figures similar to one another. An output-value determining unit determines predetermined lattice-point output values relevant to the divisions. A division selecting unit selects a division among the divisions obtained through the uneven dividing unit, the selected division corresponding to given input color-image data. An interpolating unit interpolates final output values for the given input color-image data using the lattice-point output values relevant to the division selected through the division selecting unit. The uneven dividing performed by the uneven dividing unit is that eliminating lattice points, the lattice-point output values of which are not used in the interpolating performed by the interpolating unit.

Abstract: A method for transforming input color values of a digital image to produce suitable output color values for use by a particular device is disclosed. In this method a plurality of color transforms are stored, each such transform responds to input color values of a digital image and produces output color values which can be used by the particular device. In the method an intermediate transform which is user desirable for transforming the input color values is formed by interpolating between the plurality of transforms.

Abstract: The task of transforming a description of the color of a pixel from one color space (e.g., CMYK) to another (e.g., RGB) results from (1) obtaining a first approximation of the transformation from a base lookup table, and (2) interpolating between this first approximation and a set of neighboring approximations. The interpolation task is also carried out by a loop table, in this case a second table: the delta table. The use of lookup tables for both the first approximation and interpolation tasks produces color transformations which are extremely rapid. A simplifying assumption about the nature of the delta function, the assumption of collinearity of delta functions across broad color regions, makes it possible to use a delta table of small size.

Abstract: A color printer calibration method for improving printer accuracy in regions of local non-linearity includes the steps of: a) starting with filled rectangular array of color mappings A.sub.0 mapping printer signals to device independent color space signals; b) empirically deriving a set of color mappings P.sub.i in an area of interest; c) using a set of planes defined by the color mappings of A.sub.0, and the set of empirically derived color mappings P.sub.i, identifying a new set of planes such that each point defined by A.sub.0 and each point defined by P.sub.i is located at the intersection of three planes, the intersection points of this expanded number of planes defining a set of points P.sub.i(expanded) that define a full rectangular array A.sub.1 of mappings including mappings A.sub.0, mappings P.sub.i and mappings P.sub.i(expanded) ; d) storing the mapping A.sub.1 for use in the creation of a new color space transformation LUT for use with the printer.

Abstract: In a method for transforming a color signal, a target output color signal component (X, Y, Z) is transformed into an input signal component (B, G, R) by referring to a look-up table, and a target output color signal component, which is not stored in the look-up table, is transformed into an input signal component by an interpolating process. In an output color signal space, a local coordinate system is set by using a successive approximation process, and a desired output color signal component is subjected to linear interpolation in the local coordinate system. A three-dimensional interpolating process is thus carried out quickly and accurately and over the entire color reproduction range.

Abstract: In an image forming apparatus according to the present invention, characteristic correcting data for correcting input gray level-output gray level characteristics for each of a plurality of steps into which input gray levels are divided is inputted by an inputting device. At the time of image formation processing, input gray level-output gray level characteristic data are corrected on the basis of the characteristic correcting data inputted by the inputting device. Further, when there occurs at the boundary between adjacent steps such a reversal phenomenon that an output gray level in the step having relatively low input gray levels is higher than an output gray level in the step having relatively high input gray levels in input gray level-output gray level characteristic data obtained by correction using a correcting device, the input gray level-output gray level characteristic data are so corrected that output gray levels gradually increase with higher input gray levels in the vicinity of the boundary.

Abstract: This invention provides a method for transforming an input color space to an output color space where each of a plurality of specified colors and/or color regions are constrained to be transformed by any one of a plurality of explicitly specified color calibration or color enhancement strategies. The method involves a two step process: 1) constraints are applied to some subset of the points in the input color space explicitly specifying the transform into the output color space; 2) the reminder of the points are then transformed by a mapping strategy which preserves color continuity. The mapping strategy used in the preferred embodiment is based on a computer graphics geometric morphing technique. In the preferred embodiment, multi-dimensional look-up tables are used to implement the color transformation.

Abstract: Input device signals R.sub.s, G.sub.s, B.sub.s generated by an image input terminal are converted to colorimetric values R.sub.c, G.sub.c, B.sub.c. The colorimetric values processed by an image processing unit to generate address entries to a lookup table which stores a set of transform coefficients with which the R.sub.c, G.sub.c, B.sub.c values may be processed to convert them to C.sub.x, M.sub.x, Y.sub.x, K.sub.x colorant signals or any multi-dimensional output color space, which include but are not limited to CMYK or spectral data. Values which are not directly mapped from the table are determined using tetrahedral interpolation over a hexagonal lattice. The hexagonal lattice is formed by offsetting by a half unit every other row of one of its dimensions relative to another dimension. The offset provides closer packing of sample points that define more regular tetrahedrons to reduce relative interpolation errors.

Abstract: Method and apparatus for providing interpolated image data from original image data represented in terms of pixels, each pixel defined in terms of value and position in an original image, includes an original image input receiving original image data from an original image source; a page memory operatively connected to the input for storing a page of original image received; a source of interpolation parameters indicating: a slow scan initial pixel value Xinit, a fast scan initial pixel value Yinit, a fast scan x offset value FSx, a fast scan y offset value FSy, a slow scan x offset value SSx, and a slow scan y offset value SSy; a bilinear sequencer calculating for each new pixel, from the received parameters a reference pixel within the image, and a pair of interpolation coefficients for interpolating new pixel values; a memory controller retrieving to an interpolation calculator from the page memory a set of original image pixels including the pixel at the reference position, and three other pixels whose po