US5625755A — Method and apparatus for tonal correction in bina…

Claim 1

Independent Claim 159 words

A method of printing comprising: a. obtaining a series of pixel data corresponding to a linear segment of source image; b. selecting every other one of the pixel data obtained in step a; c. filtering the pixel data selected in step b in accordance with a filter function; d. processing the pixel data filtered in step c into a halftone pattern which, when printed, exhibits a density pattern lighter than that of the source image in highlight and upper midtone regions and darker than that of the source image in shadow and lower midtone regions; and e. printing a series of dots in accordance with the halftone pattern onto a recording medium, wherein the filter function is defined such when the halftone pattern is printed, the printed pattern exhibits a density pattern lighter than that of the source image in highlight and upper midtone regions and darker than that of the source image in shadow and lower midtone regions.

Claim 2

Independent Claim 159 words

A method of printing comprising: a. obtaining a series of pixel data corresponding to a linear segment of source image; b. selecting every other one of the pixel data obtained in step a; c. filtering the pixel data selected in step b in accordance with a filter function; d. processing the pixel data filtered in step c into a halftone pattern which, when printed, exhibits a density pattern lighter than that of the source image in highlight and upper midtone regions and darker than that of the source image in shadow and lower midtone regions; and e. printing a series of dots in accordance with the halftone pattern onto a recording medium, wherein the filter function is defined such when the halftone pattern is printed, the printed pattern exhibits a density pattern lighter than that of the source image in highlight and upper midtone regions and darker than that of the source image in shadow and lower midtone regions.

Claim 3

Dependent Claim 52 words

The method of claim 1, wherein the printing step is carried out with an electronic printer having a printer transfer function f and the filter function is g(x)=N-f(N-x), where x is the density of a source data point and N is the highest gray-scale density at which the source data is represented.

Claim 4

Dependent Claim 65 words

The method of claim 1, wherein the printing step is carried out with an electronic printer having a printer transfer function f and the filter function is g(x)=2w[N-f(N-x)+x]+x, where x is the density of a source data point, N is the highest gray-scale density at which the source data is represented, and 0≦w≦1, and further comprising the step of selecting a suitable value of w.

Claim 5

Dependent Claim 14 words

The method of claim 1, wherein the processing step is accomplished by error diffusion.

Claim 6

Dependent Claim 13 words

The method of claim 1, wherein the processing step is accomplished by dithering.

Claim 7

Dependent Claim 14 words

The method of claim 5, wherein the processing step is accomplished by dispersed-dot dithering.

Claim 8

Dependent Claim 57 words

The method of claim 5, wherein the halftone-processing step comprises the steps of: a. associating each source datum with a binary raster point; b. applying a dither array to the source data; c. comparing the dithered data to a pixel threshold value; and d. selecting raster-point values based on whether corresponding dithered source data exceed the threshold.

Claim 9

Dependent Claim 51 words

The method of claim 5, wherein the halftone-processing step comprises the steps of: a. associating each source datum with a binary raster point; b. sequentially comparing the source data to numerical values in a dither array; and c. selecting raster-point values based on whether corresponding source data exceed the array values.

Claim 10

Dependent Claim 31 words

The method of claim 1, wherein each of the dots has a radius r in the range of 1/d≦r≦√2/d, and d is a resolution of the pixels in dots per inch.

Claim 11

Dependent Claim 100 words

The method of claim 1, wherein the processing step comprises the steps of: a. providing a dither array comprising a plurality of cells, each associated with a numerical value; b. associating each source datum with a binary raster point; c. modifying the cell values in accordance with a biasing function; d. applying the dither array to the source data by sequentially comparing the density values of the source data to values of cells of the dither array; and e. selecting raster-point values based on whether corresponding source-data values exceed the value of the array cells to which they are compared.

Claim 12

Dependent Claim 105 words

The method of claim 1, wherein the processing step comprises the steps of: a. associating each source datum with a binary raster point; b. providing a dither array comprising a plurality of cells, each associated with a numerical value; c. modifying the cell values in accordance with a biasing function; d. applying the dither array to the source data by adding the value of an array cell to each source datum; e. comparing the dithered source data to a pixel threshold value; and f. selecting raster-point values based on whether corresponding source-data values, which have been augmented by the array-cell values, exceed a fixed threshold.

Claim 13

Dependent Claim 39 words

The method of claim 10, wherein the biasing function is g -1 (x)=N-f -1 (N-x), where x is the density of a source data point and N is the highest gray-scale density at which the source data is represented.

Claim 14

Dependent Claim 39 words

The method of claim 11, wherein the biasing function is g -1 (x)=N-f -1 (N-x), where x is the density of a source data point and N is the highest gray-scale density at which the source data is represented.

Claim 15

Dependent Claim 52 words

The method of claim 10, wherein the biasing function is g -1 (x)=x-2w[x-N+f -1 (N-x)], where x is the density of a source data point, N is the highest gray-scale density at which the source data is represented, and 0≦w≦1, and further comprising the step of selecting a suitable value of w.

Claim 16

Dependent Claim 52 words

The method of claim 11, wherein the biasing function is g -1 (x)=x-2w[x-N+f -1 (N-x)], where x is the density of a source data point, N is the highest gray-scale density at which the source data is represented, and 0≦w≦ and further comprising the step of selecting a suitable value of w.

Claim 17

Dependent Claim 31 words

The method of claim 1, wherein each of the dots has a radius r in the range of 1/d≦r≦√2/d, and d is a resolution of the pixels in dots per inch.

Claim 18

Dependent Claim 123 words

Printing apparatus comprising: a. a source of serially encoded pixel data representative of density levels associated with a source image; b. a selector for selecting every other one of the pixel data; c. a filter for modifying the selected data in accordance with a filter function; d. a halftone engine for processing the modified data into a halftone pattern; and e. means for applying dots of ink or toner to a recording medium forming an output in accordance with the halftone pattern, wherein the filter function is defined such that the output exhibits a density pattern lighter than that of the source image in highlight and upper midtone regions and darker than that of the source image in shadow and lower midtone regions.

Claim 19

Dependent Claim 123 words

Printing apparatus comprising: a. a source of serially encoded pixel data representative of density levels associated with a source image; b. a selector for selecting every other one of the pixel data; c. a filter for modifying the selected data in accordance with a filter function; d. a halftone engine for processing the modified data into a halftone pattern; and e. means for applying dots of ink or toner to a recording medium forming an output in accordance with the halftone pattern, wherein the filter function is defined such that the output exhibits a density pattern lighter than that of the source image in highlight and upper midtone regions and darker than that of the source image in shadow and lower midtone regions.

Claim 20

Dependent Claim 46 words

The apparatus of claim 17, wherein the printing apparatus has a characteristic printer transfer function f and the filter function is g(x)=N-f(N-x), where x is the density of a source data point and N is the highest gray-scale density at which the source data is represented.

Claim 21

Dependent Claim 58 words

The apparatus of claim 17, wherein the printing apparatus has a characteristic printer transfer function f and the filter function is g(x)=2w[N-f(N-x)-x]+x, where x is the density of a source data point, N is the highest gray-scale density at which the source data is represented, and 0≦w≦1, and further comprising means for selecting a suitable value of w.

Claim 22

Dependent Claim 15 words

The apparatus of claim 17, wherein the halftone engine operates by means of error diffusion.

Claim 23

Dependent Claim 14 words

The apparatus of claim 17, wherein the halftone engine operates by means of dithering.

Claim 24

Dependent Claim 13 words

The apparatus of claim 21, wherein the halftone engine operates by dispersed-dot dithering.

Claim 25

Dependent Claim 31 words

The apparatus of claim 17, wherein each of the dots has a radius r in the range of 1/d≦r≦√2/d, and d is a resolution of the pixels in dots per inch.

Claim 26

Dependent Claim 110 words

Printing apparatus comprising: a. a source of serially encoded pixel data representative of density levels associated with a source image; b. a selector for selecting every other one of the pixel data; c. a halftone engine having a filter characteristic for processing the selected data into a raster pattern; and d. means for applying dots of ink or toner to a recording medium in accordance with the halftone pattern, wherein the filter characteristics is defined such that the output exhibits a density pattern lighter than that of the source image in highlight and upper midtone regions and darker than that of the source image in shadow and lower midtone regions.

Claim 27

Dependent Claim 110 words

Printing apparatus comprising: a. a source of serially encoded pixel data representative of density levels associated with a source image; b. a selector for selecting every other one of the pixel data; c. a halftone engine having a filter characteristic for processing the selected data into a raster pattern; and d. means for applying dots of ink or toner to a recording medium in accordance with the halftone pattern, wherein the filter characteristics is defined such that the output exhibits a density pattern lighter than that of the source image in highlight and upper midtone regions and darker than that of the source image in shadow and lower midtone regions.

Claim 28

Dependent Claim 49 words

The apparatus of claim 24, wherein the halftone engine is biased according to the function g -1 (x)=N-f -1 (N-x), where x is the density of a source data point and N is the highest gray-scale density at which the source data is represented, to produce the density pattern.

Claim 29

Dependent Claim 54 words

The apparatus of claim 24, wherein the halftone engine is biased according to g -1 (x)=x-2w[x-N+f -1 (N-x)], where x is the density of a source data point, N is the highest gray-scale density at which the source data is represented, and 0≦w≦1, and further comprising means for selecting a suitable value of w.

Claim 30

Dependent Claim 31 words

The apparatus of claim 24, wherein each of the dots has a radius r in the range of 1/d≦r≦√2/d, and d is a resolution of the pixels in dots per inch.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2000-04-28	2000-10-28	2001-04-29	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2004-04-28	2004-10-28	2005-04-29	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2008-04-28	2008-10-28	2009-04-29	$7700.00	Window Closed / Lapsed

Method and apparatus for tonal correction in binary printing devices by predistortion of image data utilizing ink reduction processing

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