US4996602A
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Image-processing apparatus
Assignee: Mitsubishi Electric Corp
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Filing: 1989-05-23
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Granted: 1991-02-26
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Expires: 2009-05-23
Abstract
Abstract An input gray-scale image is converted to a bilevel output signal by an image-processing apparatus with two binarizing circuits: one employing a uniform threshold and the other a dither matrix. The outputs of these circuits are selected for each pixel by deciding whether the pixel is a bilevel pixel or a gray-scale pixel. The decision is based on the maximum and minimum gray levels in a block of pixels centered on the pixel in question. Images having both bilevel and gray-scale parts can thus be binarized with clean reproduction of black-white edges.
Inventors
- 👤 Fumitaka Ono
- 👤 Takayoshi Semasa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 17:20
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/40062
Claims Analysis
Total Claims: 36
Claim 1
Independent Claim
184 words
An image-processing apparatus for converting an input image having pixels with multiple gray levels to a bilevel output signal, comprising: gray-scale image memory means for storing said input image; maximum-minimum detection means for reading said stored input image from said gray-scale image memory means, testing respective blocks of plural pixels centered on respective pixels of said stored input image, finding the maximum and minimum gray levels therein, and furnishing said maximum and minimum gray levels as output; decision means for receiving said maximum and minimum gray levels, deciding therefrom whether respective pixels are gray-scale pixels or bilevel pixels, and generating a control signal accordingly; uniform-threshold binarizing means for receiving said stored input image read by said maximum-minimum detection means, thresholding it against a uniform threshold, and thereby generating a first bilevel signal; dither-matrix binarizing means for receiving said stored input image read by said maximum-minimum detection means, thresholding it using a dither matrix, and thereby generating a second bilevel signal; and switch means for selecting said first bilevel signal or said second bilevel signal, according to said control signals, as said bilevel output signal.
Claim 2
Dependent Claim
184 words
An image-processing apparatus for converting an input image having pixels with multiple gray levels to a bilevel output signal, comprising: gray-scale image memory means for storing said input image; maximum-minimum detection means for reading said stored input image from said gray-scale image memory means, testing respective blocks of plural pixels centered on respective pixels of said stored input image, finding the maximum and minimum gray levels therein, and furnishing said maximum and minimum gray levels as output; decision means for receiving said maximum and minimum gray levels, deciding therefrom whether respective pixels are gray-scale pixels or bilevel pixels, and generating a control signal accordingly; uniform-threshold binarizing means for receiving said stored input image read by said maximum-minimum detection means, thresholding it against a uniform threshold, and thereby generating a first bilevel signal; dither-matrix binarizing means for receiving said stored input image read by said maximum-minimum detection means, thresholding it using a dither matrix, and thereby generating a second bilevel signal; and switch means for selecting said first bilevel signal or said second bilevel signal, according to said control signals, as said bilevel output signal.
Claim 3
Dependent Claim
41 words
The image-processing apparatus of claim 1, wherein said decision means decides whether a pixel is a gray-scale pixel or bilevel pixel according to whether the difference between said maximum and minimum gray levels is less than a certain value or not.
Claim 4
Dependent Claim
15 words
The image-processing apparatus of claim 2, wherein said certain value is the middle gray level.
Claim 5
Dependent Claim
15 words
The image-processing apparatus of claim 1, wherein said uniform threshold is the middle gray level.
Claim 6
Dependent Claim
25 words
The image-processing apparatus of claim 1, wherein the size of said respective blocks tested by said maximum-minimum detection means is three pixels by three pixels.
Claim 7
Independent Claim
126 words
A method of converting an input image having pixels with multiple gray levels to a bilevel output signal, comprising the steps of: testing respective blocks of plural pixels centered on respective pixels in said input image and finding the maximum and minimum gray levels therein; deciding from said maximum and minimum gray levels whether each respective pixel is a gray-scale pixel or a bilevel pixel; threshold a respective pixel against a uniform threshold if said respective pixel is decided to be a bilevel pixel to generate a first bilevel signal as said bilevel output signal; and thresholding a respective pixel using a dither matrix if said respective pixel is decided to be a gray-scale pixel to generate a second bilevel signal s said bilevel output signal.
Claim 8
Independent Claim
126 words
A method of converting an input image having pixels with multiple gray levels to a bilevel output signal, comprising the steps of: testing respective blocks of plural pixels centered on respective pixels in said input image and finding the maximum and minimum gray levels therein; deciding from said maximum and minimum gray levels whether each respective pixel is a gray-scale pixel or a bilevel pixel; threshold a respective pixel against a uniform threshold if said respective pixel is decided to be a bilevel pixel to generate a first bilevel signal as said bilevel output signal; and thresholding a respective pixel using a dither matrix if said respective pixel is decided to be a gray-scale pixel to generate a second bilevel signal s said bilevel output signal.
Claim 9
Dependent Claim
37 words
The method of claim 6, wherein a pixel is decided to be a gray-scale or bilevel pixel according to whether the difference between said maximum and minimum gray levels is less than a certain value or not.
Claim 10
Dependent Claim
14 words
The method of claim 7, wherein said certain value is the middle gray level.
Claim 11
Dependent Claim
14 words
The method of claim 6, wherein said uniform threshold is the middle gray level.
Claim 12
Dependent Claim
19 words
The method of claim 6, wherein the size of said respective blocks tested is three pixels by three pixels.
Claim 13
Dependent Claim
185 words
An image-processing apparatus for converting an input image having pixels with multiple gray levels to a bilevel output signal, comprising: gray-scale image memory means for storing said input image; maximum-minimum detection means for reading said stored input image from said gray-scale image memory means, for each respective pixel therein finding maximum and minimum gray levels in a block of plural pixels centered on and including said respective pixel, and furnishing said maximum and minimum gray levels as output; decision means for receiving said maximum and minimum gray levels, deciding therefrom whether respective pixels are gray-scale pixels or bilevel pixels, and generating a control signal accordingly; uniform-threshold binarizing means for receiving said stored input image read by said maximum-minimum detection means, thresholding it against a uniform threshold, and thereby generating a first bilevel signal; dither-matrix binarizing means for receiving said stored input image read by said maximum-minimum detection means, thresholding it using a dither matrix, and thereby generating a second bilevel signal; and switch means for selecting said first bilevel signal or said second bilevel signal, according to said control signal, as said bilevel output signal.
Claim 14
Dependent Claim
185 words
An image-processing apparatus for converting an input image having pixels with multiple gray levels to a bilevel output signal, comprising: gray-scale image memory means for storing said input image; maximum-minimum detection means for reading said stored input image from said gray-scale image memory means, for each respective pixel therein finding maximum and minimum gray levels in a block of plural pixels centered on and including said respective pixel, and furnishing said maximum and minimum gray levels as output; decision means for receiving said maximum and minimum gray levels, deciding therefrom whether respective pixels are gray-scale pixels or bilevel pixels, and generating a control signal accordingly; uniform-threshold binarizing means for receiving said stored input image read by said maximum-minimum detection means, thresholding it against a uniform threshold, and thereby generating a first bilevel signal; dither-matrix binarizing means for receiving said stored input image read by said maximum-minimum detection means, thresholding it using a dither matrix, and thereby generating a second bilevel signal; and switch means for selecting said first bilevel signal or said second bilevel signal, according to said control signal, as said bilevel output signal.
Claim 15
Dependent Claim
41 words
The image-processing apparatus of claim 11, wherein said decision means decides whether a pixel is a gray-scale pixel or bilevel pixel according to whether the difference between said maximum and minimum gray levels is less than a certain value or not.
Claim 16
Dependent Claim
23 words
The image-processing apparatus of claim 11, wherein the block of plural pixels tested by said maximum-minimum detection means is three by three pixels.
Claim 17
Dependent Claim
15 words
The image-processing apparatus of claim 12, wherein said certain value is the middle gray level.
Claim 18
Dependent Claim
15 words
The image-processing apparatus of claim 11, wherein said uniform threshold is the middle gray level.
Claim 19
Independent Claim
130 words
A method of converting an input image having pixels with multiple gray levels to a bilevel output signal, comprising the steps of: testing each respective pixel in said input image for finding maximum and minimum gray levels in a block of plural pixels centered on and including said respective pixel; deciding from said maximum and minimum gray levels whether each respective pixel is gray-scale pixel or a bilevel pixel; thresholding a respective pixel against a uniform threshold if said respective pixel is decided to be a bilevel pixel to generate a first bilevel signal as said bilevel output signal; and thresholding a respective pixel using a dither matrix if said respective pixel is decided to be a gray-scale pixel to generate a second bilevel signal as said bilevel output signal.
Claim 20
Independent Claim
130 words
A method of converting an input image having pixels with multiple gray levels to a bilevel output signal, comprising the steps of: testing each respective pixel in said input image for finding maximum and minimum gray levels in a block of plural pixels centered on and including said respective pixel; deciding from said maximum and minimum gray levels whether each respective pixel is gray-scale pixel or a bilevel pixel; thresholding a respective pixel against a uniform threshold if said respective pixel is decided to be a bilevel pixel to generate a first bilevel signal as said bilevel output signal; and thresholding a respective pixel using a dither matrix if said respective pixel is decided to be a gray-scale pixel to generate a second bilevel signal as said bilevel output signal.
Claim 21
Dependent Claim
37 words
The method of claim 16, wherein a pixel is decided to be a gray-scale or bilevel pixel according to whether the difference between said maximum and minimum gray levels is less than a certain value or not.
Claim 22
Dependent Claim
18 words
The method of claim 16, wherein the block of plural pixels tested is three pixels by three pixels.
Claim 23
Dependent Claim
14 words
The method of claim 17, wherein said certain value is the middle gray level.
Claim 24
Dependent Claim
14 words
The method of claim 16, wherein said uniform threshold is the middle gray level.
Claim 25
Dependent Claim
133 words
An image processing apparatus comprising: maximum-minimum detection means for testing each respective pixel with a block of plural pixels centered on and including said respective pixel to generate and output maximum and minimum gray levels for each respective pixel of a stored image of multiple gray levels; decision means, coupled to and receiving said maximum and minimum gray levels, for determining therefrom whether each respective pixel is a gray-scale pixel or a bilevel pixel and for outputting a decision signal indicative thereof; and binarizing means, coupled to and receiving said decision signal, for thresholding a respective pixel against a uniform threshold if the respective pixel is a bilevel pixel and for thresholding a respective pixel using a dither matrix if the respective pixel is a gray-scale pixel, to generate a bilevel output signal.
Claim 26
Dependent Claim
133 words
An image processing apparatus comprising: maximum-minimum detection means for testing each respective pixel with a block of plural pixels centered on and including said respective pixel to generate and output maximum and minimum gray levels for each respective pixel of a stored image of multiple gray levels; decision means, coupled to and receiving said maximum and minimum gray levels, for determining therefrom whether each respective pixel is a gray-scale pixel or a bilevel pixel and for outputting a decision signal indicative thereof; and binarizing means, coupled to and receiving said decision signal, for thresholding a respective pixel against a uniform threshold if the respective pixel is a bilevel pixel and for thresholding a respective pixel using a dither matrix if the respective pixel is a gray-scale pixel, to generate a bilevel output signal.
Claim 27
Dependent Claim
20 words
The image processing apparatus of claim 21 wherein the block of plural pixels tested is three pixels by three pixels.
Claim 28
Dependent Claim
43 words
The image processing apparatus of claim 21 wherein said decision means decides whether a pixel is a gray-scale pixel or a bilevel pixel according to whether the difference between said maximum and minimum gray levels is less than a certain value or not.
Claim 29
Dependent Claim
16 words
The image processing apparatus of claim 23 wherein said certain value is the middle gray level.
Claim 30
Dependent Claim
16 words
The image processing apparatus of claim 21 wherein said uniform threshold is the middle gray level.
Claim 31
Independent Claim
116 words
A method of image processing comprising the steps of: testing each respective pixel and a block of plural pixels centered on and including said respective pixel to generate and output maximum and minimum gray levels for each respective pixel of a stored image of multiple gray levels; determining in response to said maximum and minimum gray levels, whether each respective pixel is a gray-scale pixel or a bilevel pixel and outputting a decision signal indicative thereof; and binarizing a respective pixel against a uniform threshold if the respective pixel is a bilevel pixel and binarizing a respective pixel using a dither matrix if the respective pixel is a gray-scale pixel, to generate a bilevel output signal.
Claim 32
Independent Claim
116 words
A method of image processing comprising the steps of: testing each respective pixel and a block of plural pixels centered on and including said respective pixel to generate and output maximum and minimum gray levels for each respective pixel of a stored image of multiple gray levels; determining in response to said maximum and minimum gray levels, whether each respective pixel is a gray-scale pixel or a bilevel pixel and outputting a decision signal indicative thereof; and binarizing a respective pixel against a uniform threshold if the respective pixel is a bilevel pixel and binarizing a respective pixel using a dither matrix if the respective pixel is a gray-scale pixel, to generate a bilevel output signal.
Claim 33
Dependent Claim
21 words
The method of image processing of claim 26 wherein the block of plural pixels tested is three pixels by three pixels.
Claim 34
Dependent Claim
45 words
The method of image processing of claim 26 wherein said determining step comprises deciding whether a pixel is a gray-scale pixel or a bilevel pixel according to whether the difference between said maximum and minimum gray levels is less than a certain value or not.
Claim 35
Dependent Claim
17 words
The method of image processing of claim 28 wherein said certain value is the middle gray level.
Claim 36
Dependent Claim
17 words
The method of image processing of claim 26 wherein said uniform threshold is the middle gray level.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-02-25 | 1994-08-27 | 1995-02-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-02-25 | 1998-08-27 | 1999-02-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-02-25 | 2002-08-27 | 2003-02-26 | $7700.00 | Window Closed / Lapsed |