EP0500267A2
Expired / Lapsed
EP
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Image processing system
Assignee: AT&T Inc
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Filing: 1992-02-13
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Granted: —
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Expires: 2012-02-13
Abstract
Abstract An image-processing system for perceptual coding of images by analyzing one or more images to determine levels of imperceptible noise and encoding a first image to produce encoded values without introducing noise exceeding a determined level of imperceptible noise is disclosed. Analyzing of images is carried out under a set of user determined conditions comprising viewing distance and lighting. The encoded image is communicated and decoded to produce representation of the first image for display. As part of displaying the representation of the first image, a halftoning process is carried out. The halftoning process may comprise the interpolation of data values of the representation of the first image as well as the addition of micro-dither to the representation. Illustrative halftoning techniques include classical halftoning, least-squares halftoning, and error diffusion halftoning. Printer model-based halftoning techniques for both least-squares halftoning and error diffusion halftoning are presented. Applications of the model-based halftoning techniques for systems employing conventional coding of images are also discussed.
Inventors
- 👤 James David Johnston
- 👤 David Lee Neuhoff
- 👤 Thrasyvoulos Nicholaou Pappas
- 👤 Robert James Safranek
- 👤 Nambirajan Seshadri
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 11:46
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/405; H04N1/4051; H04N1/4052; H04N1/41; H04N1/4105; H04N19/00; H04N19/60; H04N19/61; H04N19/63; H04N19/90; H04N19/94; H04N5/00; H04N5/76; H04N5/91; H04N5/92; H04N5/926; H04N5/9261; H04N19/10; H04N19/102; H04N19/13; H04N19/50; H04N5/84; H04N5/85
Claims Analysis
Total Claims: 37
Claim 1
Independent Claim
94 words
A method for generating an array of output binary signals suitable for application to a display device to generate a halftone image in response to an array of input signals characterizing a gray scale image, said method comprising the steps of modifying each of said input signals in response to error signals, said error signals reflecting differences between said modified input signals and signals predictive of regions of halftone images formed by said display device in response to applied binary signals, forming a binary digit in response to each of said modified input signals.
Claim 2
Independent Claim
94 words
A method for generating an array of output binary signals suitable for application to a display device to generate a halftone image in response to an array of input signals characterizing a gray scale image, said method comprising the steps of modifying each of said input signals in response to error signals, said error signals reflecting differences between said modified input signals and signals predictive of regions of halftone images formed by said display device in response to applied binary signals, forming a binary digit in response to each of said modified input signals.
Claim 3
Dependent Claim
49 words
The method of claim 1 wherein said forming of a binary digit comprises assigning one value to said binary digit whenever said modified input signal exceeds a threshold value, and assigning the other value to said binary digit whenever said modified input signal fails to exceed said threshold value.
Claim 4
Dependent Claim
34 words
The method of claim 1 wherein the number of input signals in said army of input signals is adjusted to be equal to the number of signals in said array of output binary signals.
Claim 5
Dependent Claim
64 words
The method of claim 3, wherein for the case of the number of input signals in said army of input signals being less than the number of signals in said array of output binary signals, the number of input signals is adjusted by creating additional input signals, the value of said additional input signals being determined by interpolation based on selected neighboring input signals.
Claim 6
Dependent Claim
46 words
The method of claim 1 wherein said array of input signals is ordered in accordance with the respective position in said image, and said binary signals used to generate said predicted halftone image comprise binary signals corresponding to one or more prior positions in said order.
Claim 7
Dependent Claim
32 words
The method of claim 5 wherein said binary signals used to generate said predicted halftone image comprises binary signals corresponding to one or more subsequent positions in said regions of halftone images.
Claim 8
Independent Claim
152 words
A method for generating an army of output binary signals suitable for application to a display device to generate a halftone image in response to an army of input signals characterizing a gray scale image, said method comprising the steps of filtering said input signals using an eye-model filter reflecting characteristics of human vision to derive first signals representative of an estimate of the gray scale image as perceived by the eye, filtering sequences of binary signals using a filter reflecting characteristics representative of said display device to produce second signals representing an estimate of the output of said display device, filtering said second signals using a said eye-model filter to produce third signals, forming an error signal representative of the difference between said first and third signals, and selecting as the binary signals to be applied to said printing device that sequence which realizes some preselected criterion for said error signal.
Claim 9
Independent Claim
152 words
A method for generating an army of output binary signals suitable for application to a display device to generate a halftone image in response to an army of input signals characterizing a gray scale image, said method comprising the steps of filtering said input signals using an eye-model filter reflecting characteristics of human vision to derive first signals representative of an estimate of the gray scale image as perceived by the eye, filtering sequences of binary signals using a filter reflecting characteristics representative of said display device to produce second signals representing an estimate of the output of said display device, filtering said second signals using a said eye-model filter to produce third signals, forming an error signal representative of the difference between said first and third signals, and selecting as the binary signals to be applied to said printing device that sequence which realizes some preselected criterion for said error signal.
Claim 10
Dependent Claim
20 words
The method of claim 7 wherein said selecting of said binary digits is accomplished in accordance with a Viterbi algorithm.
Claim 11
Independent Claim
125 words
A method for generating an array of output binary signals suitable for application to a display device to generate a halftone image in response to an array of input signals characterizing a gray scale image, said method comprising the steps of: (a) filtering sequences of binary signals using a two-dimensional filter reflecting characteristics representative of said display device to produce first signals representing an estimate of the output of said display device; (b) filtering said first signals using an eye-model filter to produce second signals; (c) forming an error signal representative of a difference between said input and second signals; and (d) selecting as the binary signals to be applied to said display device that sequence which realizes some preselected criterion for said error signal.
Claim 12
Independent Claim
125 words
A method for generating an array of output binary signals suitable for application to a display device to generate a halftone image in response to an array of input signals characterizing a gray scale image, said method comprising the steps of: (a) filtering sequences of binary signals using a two-dimensional filter reflecting characteristics representative of said display device to produce first signals representing an estimate of the output of said display device; (b) filtering said first signals using an eye-model filter to produce second signals; (c) forming an error signal representative of a difference between said input and second signals; and (d) selecting as the binary signals to be applied to said display device that sequence which realizes some preselected criterion for said error signal.
Claim 13
Dependent Claim
29 words
The method of claim 9 wherein the step of forming an error signal comprises the step of minimizing the squared error over a portion said input and second signals.
Claim 14
Dependent Claim
16 words
The method of claim 10 wherein the portion of said second signal comprises a binary signal.
Claim 15
Dependent Claim
12 words
The method of claim 9 wherein an eye-model comprises a two-dimensional eye-model.
Claim 16
Dependent Claim
58 words
The method of claim 9 further comprising the step of altering said input signals using an eye-model filter reflecting characterisrics of human vision to provide input signals representative of an estimate of the greyscale image as perceived by the eye, the step of filtering said input signals being performed prior to said step of forming an error signal.
Claim 17
Independent Claim
79 words
A method for communicating a first image, the method comprising the steps of: analyzing one or more images to determine one or more levels of imperceptible noise; encoding the first image to produce one or more encoded values without introducing in a value noise which exceeds a determined level of imperceptible noise; communicating the one or more encoded values; decoding the encoded values to produce a representation of the first image; and displaying a representation of the first image.
Claim 18
Independent Claim
79 words
A method for communicating a first image, the method comprising the steps of: analyzing one or more images to determine one or more levels of imperceptible noise; encoding the first image to produce one or more encoded values without introducing in a value noise which exceeds a determined level of imperceptible noise; communicating the one or more encoded values; decoding the encoded values to produce a representation of the first image; and displaying a representation of the first image.
Claim 19
Dependent Claim
18 words
The method of claim 14 wherein the step of communicaring comprises the step of storing the encoded values.
Claim 20
Dependent Claim
32 words
The method of claim 14 wherein the step of displaying a representation of the first image comprises the step of determining a halftoned image based on the representation of the first image.
Claim 21
Dependent Claim
26 words
The method of claim 16 wherein the step of determining a halftoned image comprises the step of adding micro-dither to a representation of the first image.
Claim 22
Dependent Claim
27 words
The method of claim 16 wherein the step of determining a halftoned image comprises the step of performing classical screening on a representation of the first image.
Claim 23
Dependent Claim
42 words
The method of claim 16 wherein the decoded representation of the first image comprises data values and wherein the step of determining a halftoned image comprises the step of interpolating to provide additional data values for a representation of the first image.
Claim 24
Dependent Claim
33 words
The method of claim 19 wherein the step of determining a halftoned image further comprises the step of performing classical screening on the representation of the first image afterthe step of adding micro-dither.
Claim 25
Dependent Claim
17 words
The method of claim 16 wherein the haltoned image is determined with a printer model-based halftoning technique.
Claim 26
Dependent Claim
92 words
The method of claim 16 wherein the represenation of the first image comprises one or more input signals, wherein the halftoned image is represented by one or more output signals, and wherein the step of determining a halftoned image comprises the steps of: modifying each of the input signals in response to error signals, the error signals reflecting differences between the modified input signals and signals predictive of regions of halftone images displayed in response to binary signals; and forming a binary digit in response to each of the modified input signals.
Claim 27
Dependent Claim
154 words
The method of claim 16 wherein the representation of the first image comprises one or more input signals, wherein the halftoned image is represented by one or more output signals, and wherein the step of determining a halftoned image comprises the step of: filtering said input signals using an eye-model filter reflecting characteristics of human vision to derive first signals representative of an estimate of the gray scale image as perceived by the eye, filtering sequences of binary signals using a filter reflecting characteristics representative of said display device to produce second signals representing an estimate of the output of said display device, filtering said second signals using a said eye-model filter to produce third signals, forming an error signal representative of the difference between said first and third signals, and selecting as the binary signals to be applied to said display device that sequence which realises some preselected criterion for said error signal.
Claim 28
Independent Claim
53 words
A method for communicating an image for printing comprising the steps of: encoding the image and transmitting its encoded representation; receiving the encoded representation of the image and decoding it; determining a haltoned image based on the decoded representation of the image with a printer model-based halftoning technique; and printing the halftoned image.
Claim 29
Independent Claim
53 words
A method for communicating an image for printing comprising the steps of: encoding the image and transmitting its encoded representation; receiving the encoded representation of the image and decoding it; determining a haltoned image based on the decoded representation of the image with a printer model-based halftoning technique; and printing the halftoned image.
Claim 30
Dependent Claim
91 words
The method of claim 24 wherein the representation of the image comprises one or more input signals, wherein the halftoned image is represented by one or more output signals, and wherein the step of determining a halftoned image comprises the steps of: modifying each of the input signals in response to error signals, the error signals reflecting differences between the modified input signals and signals predictive of regions of halftone images displayed in response to binary signals; and forming a binary digit in response to each of the modified input signals.
Claim 31
Dependent Claim
153 words
The method of claim 24 wherein the representation of the image comprises one or more input signals, wherein the halftoned image is represented by one or more output signals, and wherein the step of determining a halftoned image comprises the steps of: filtering said input signals using an eye-model filter reflecting characteristics of human vision to derive first signals representative of an estimate of the gray scale image as perceived by the eye, filtering sequences of binary signals using a filter reflecting characteristics representative of said display device to produce second signals representing an estimate of the output of said display device, filtering said second signals using a said eye-model filter to produce third signals, forming an error signal representative of the difference between said first and third signals, and selecting as the binary signals to be applied to said display device that sequence which realizes some preselected criterion for said error signal.
Claim 32
Dependent Claim
160 words
The method of claim 16 or 24 wherein the representation of the image comprises one or more input signals, wherein the halftoned image is represented by one or more output signals, and wherein the step of determining a halftoned image comprises the steps of: (a) filtering said input signals using an eye-model filter reflecting characteristics of human vision to derive first signals representative of an estimate of the gray scale image as perceived by the eye; (b) filtering sequences of binary signals using a two-dimensional filter reflecting characteristics representative of said display device to produce second signals representing an estimate of the output of said display device; (c) filtering said second signals using an eye-model filter to produce third signals; (d) forming an error signal representative of a difference between said first and third signals; and (e) selecting as the binary signals to be applied to said display device that sequence which realizes some preselected criterion for said error signal.
Claim 33
Dependent Claim
41 words
The method of claim 9 or 27 wherein the step of selecting comprises the steps of: (1) providing initial sequences of binary signals; and (2) performing an iterative process to determine the binary signals to be applied to the display device.
Claim 34
Dependent Claim
27 words
The method of claim 28 wherein the step of providing initial sequences of binary signals comprises the step of performing a halftoning technique on the gray-scale image.
Claim 35
Dependent Claim
83 words
The method of claim 28 wherein the step of performing an iterative process comprises the steps of: (i) changing the logical value of one or more binary signals of a sequence of binary signals; (ii) performing steps (b), (c) and (d); and (iii) if the error signal has been increased as a result of a changed logical value of the one or more binary signals, restoring the logical value of the one or more binary signals to the value prior to step (1).
Claim 36
Dependent Claim
23 words
The method of claim 29 wherein the step of performing a halftoning technique comprises the step of performing modified error diffusion model-based halftoning.
Claim 37
Dependent Claim
22 words
The method of claim 29 wherein the step of performing a halftoning technique comprises the step of performing one-dimensional least-squares modelbased halftoning.
References Cited (Backward Citations)
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