Lexmark International, Inc.

Brian Edward Cooper

Shaun Timothy Love

Mohamed Nooman Ahmed

Michael E Lhamon

Brian Wesley Damon

Thomas Campbell Wade

Steven Frank Weed

Paul Athanasius Robinson

Chengwu Cui

Bryan Scott Willett

Thomas Anthony Knight

Mary Ellen Biddle

Buford Rodney Goble

Ross William McFarland

A system can include a system processor that is programmed or adapted to classify pixels in a document image, and in some instances, to enhance the document image based upon such classification. Image data including pixels is received. For each pixel in some subset of the image data, a feature vector is generated. Each pixel in the subset is classified as text or image based upon its associated feature vector. The classifications can be outputted for storage and/or further processing. Further processing can include pixel level enhancement processing. Such enhancement processing can include application of a sharpening filter to pixels classified as text and of a smoothing filter to pixels classified as image. In some instances, background suppression can be performed upon a subset of the image data prior to classification.

Systems and methods for content-based document image enhancement

The input pixels in an image to be halftoned using error diffusion are dithered using a first type of passband dither. A second type of passband dither may also be added to a thresholding matrix used in halftoning. This second type of passband dither may be the same as the first type of passband dither. In such case, the second type of passband dither is a scaled multiple of the first type of passband dither. The halftoning process may be implemented in an application specific integrated circuit.

Apparatus and method for error diffusion with dither

A method for copying objects smaller than a background defined by a scanner of an apparatus includes scanning a plurality of objects to acquire image data associated with the plurality of objects and the background; cropping the image data to remove object data for each object of the plurality of objects from the background; determining a size associated with each object of the plurality of objects, based on the object data; and formatting a page to produce a compact arrangement of multiple objects of the plurality of objects on the page, the page receiving the multiple objects in accordance with the size.

Method for copying objects

The invention provides a system and method for JPEG encoding an image that includes variable quantization for each block, depending upon the classification of each block, which is dependent on the classification of pixels in that block.

JPEG encoding for document images using pixel classification

A printer that stores a minimal number of unadjusted stochastic threshold arrays in non-volatile memory, in which the unadjusted threshold arrays are used to generate adjusted threshold arrays at run time by use of special parameterized transfer functions. The unadjusted array for a particular color is stored in the printer's ROM and preferably is stored in a packed configuration to save memory space. The parameterized transfer functions are used to convert the unadjusted threshold data into adjusted threshold data for each color and type of print media. These parameterized transfer functions are stored in the printer's non-volatile memory, and take up very little memory space. In a preferred embodiment, the unadjusted threshold array comprises a 128 row by 128 column sized array, and each element of this array comprises a 10-bit number. When a parameterized transfer function is applied to this unadjusted array, the resulting numeric values for the adjusted array elements are produced as 8-bit numeric values. The greater precision in the originating unadjusted array provides more perceptual levels of intensity (i.e., color brightness), which is particularly important at the lighter shades of each color. The adjusted threshold arrays add only the number of dots per gray level (i.e., per differential threshold array level) that are required to provide a printer response that very nearly approximates the human eye perceptual differential response of intensity.

Method for correcting unadjusted threshold arrays for halftoning by use of parameterized transfer functions that generate adjusted threshold arrays at run time

An improved shingle mask is provided for use on ink jet printers which use multi-pass printing (shingling) to form bitmap images. The shingle mask is derived from a shingle mask density distribution which exhibits a substantially trapezoidal shape; the shingle mask density distribution is derived from an accumulated shingle mask distribution (also referred to as a &ldquo;banding profile&rdquo;) having an overall shape of a plateau portion and a substantially smooth decreasing portion, which reduces the number of drops to be printed along the outermost edges of the mask on each swath. This shape reduces banding effects by effectively increasing a number of printed-density bands which are decreased in size, while at the same time not increasing the number of printhead passes over a given area on the print media (which otherwise would negatively impact printed throughput).

Shingle masks that reduce banding effect on ink jet printers

An improved method of digital halftoning using &ldquo;screens&rdquo; or dither arrays is provided, including stochastic dither arrays (e.g., stochastic screening). The weakness of ordinary stochastic dithering is its isolated or dispersed dots and the related problems of dot gain and consistent dot formation when used with certain types of printers. However, the inconsistent formation of isolated dots causes unpredictable variations in uniformity and tone. The present invention solves this problem by grouping dots into small clusters, which may be rendered more consistently. Unlike conventional clustered-dot halftoning, however, this method arranges the dot clusters in a stochastic fashion to avoid objectionable periodic artifacts. A novel weighting function is used to generate the dot clusters, in which one function of a first extent is subtracted from another function of a second extent, thereby creating clusters of dots that center at locations where the weighting function chooses to place dots. Locations very close to an existing dot will have an increased chance of being selected; at a certain distance away from the existing dot, where the new weighting function reaches a maximum (or maxima), locations will have a smaller chance of being selected; once past this distance, the locations will have a gradually increasing chance of selection.

Method for halftoning using a difference weighting function

A printer that stores a minimal number of unadjusted stochastic threshold arrays in non-volatile memory, in which the unadjusted threshold arrays are used to generate adjusted threshold arrays at run time by use of Transfer Function Tables (TFT's). The unadjusted array for a particular color is stored in the printer's ROM and preferably is stored in a packed configuration to save memory space. The TFT's are used to convert the unadjusted threshold data into adjusted threshold data for each color and type of print media. In a preferred embodiment, the unadjusted threshold array comprises a 128 row by 128 column sized array, and each element of this array comprises a 10-bit number. When the TFT is applied to this unadjusted array, the resulting numeric values for the adjusted array elements are produced as 8-bit numeric values. The greater precision in the originating unadjusted array provides more perceptual levels of intensity (i.e., color brightness), which is particularly important at the lighter shades of each color. The adjusted threshold arrays add only the number of dots per gray level (i.e., per differential threshold array level) that are required to provide a printer response that very nearly approximates the human eye perceptual differential response of intensity.

Method and apparatus for correcting unadjusted threshold arrays for halftoning by use of transfer function tables

Method and apparatus for correcting unadjusted threshold arrays for halftoning by use of parameterized transfer functions that generate adjusted threshold arrays at run time

A dispersed-dot stochastic dither array is provided for rendering halftone images having excellent visual quality. For color printing, a separate threshold array is generated for each of the color planes, however, the stochastic screens are interlocked so that the threshold arrays are generated while considering the other color threshold arrays. In this manner, a blue noise distribution may be produced by the individual arrays as well as by any combination of the individual arrays. When generating a single threshold array for a color plane, a particular criterion is used to determine where the next threshold value should be located, and the selection of a threshold location in each array considers the criterion for all the threshold arrays being generated. By using the interlocked threshold arrays approach, the overall visual affect will be improved for both individual threshold arrays and for a combination of more than one of the threshold arrays. The present invention also is used to generating a set of interlocked dot profiles which do not use a threshold array for halftoning. In an opposite sense, the interlocked threshold arrays can be generated without using dot profiles during the formative steps of the threshold array. More than one threshold array could be generated in this manner, and these threshold arrays could also be interlocked with respect to one another. Other alternative methodologies include globally optimizing interlocked threshold arrays by simultaneously considering all tone levels for all threshold arrays being generated to avoid locally suboptimal solutions; or regional optimization can be achieved to simultaneously considering certain portions of the tone levels. Also, interlocked threshold arrays can be created that obtain better data compression, or to embed a digital watermark.

Method for halftoning using interlocked threshold arrays or interlocked dot profiles

A dispersed-dot stochastic dither array is provided for rendering halftone images having excellent visual quality and are created by a minimum density variance method. By minimizing the variance in the number of dots within each local region of the image, a smooth and dispersed distribution of dots may be obtained. For color printing, a separate threshold array is generated for each of the color planes, however, the stochastic screens are interlocked so that the threshold arrays are generated while considering the other color threshold arrays. In this manner, a blue noise distribution may be produced by the individual arrays as well as by any combination of the individual arrays. When generating a single threshold array for a color plane, a particular criterion is used to determine where the next threshold value should be located, and the selection of a threshold location in each array considers the criterion for all the threshold arrays being generated. This may reduce the quality of an individual array by a small amount, but it allows for the combination of the arrays to have a significantly better distribution. The simplest approach uses the average of the criteria for all threshold arrays, however, to improve the quality of the individual arrays, the preferred method of the present invention uses a weighted average. When selecting a threshold location for an array 'i' using weighted averages, the criterion associated with array i may be assigned a greater weight than each of the other individual arrays' criteria. By using the interlocked stochastic screens approach, the overall visual affect will be improved for both individual threshold arrays and for a combination of more than one of the threshold arrays. The interlocked approach is clearly superior for lighter shades, given any number of color planes.

Method and apparatus for color halftoning using interlocked threshold

A dispersed-dot stochastic dither array is provided for rendering halftone images having excellent visual quality and are created by a minimum density variance method. The minimum density variance method considers the statistical distribution of the pixels in the image, and is unrelated to previous techniques based on either spatial frequencies or spatial distances, such as the blue noise mask and the void and cluster algorithm. By minimizing the variance in the number of dots within each local region of the image, a smooth and dispersed distribution of dots may be obtained. The method of the present invention also offers the flexibility to accommodate particular design considerations, through the selection of the size and shape of the image regions, the weighting of the cost function, and the option of guiding the selection of dots with 'target' dot profile images.

Growing community of inventors

Lexington, KY, United States of America

Brian Edward Cooper