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US5361142A
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Image processing apparatus and method for multi-level image signal
Assignee: Mitsubishi Electric Corp
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Filing: 1993-12-03
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Granted: 1994-11-01
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Expires: 2013-12-03
Abstract
Abstract An image processing apparatus for outputting an image which contains different kinds of multi-level signals for letters, figures, photographs, screened-halftone, etc. The apparatus comprises a screened-halftone pattern detecting circuit and a continuous-tone pattern detecting circuit for detecting a screened-halftone pattern and a continuous-tone pattern, respectively, by using neighboring pixels of the target pixel, counters for counting UP/DOWN in accordance with the outputs of the detecting circuits, a filter for switching the filtering coefficients of the image signal in multiple stages in accordance with the outputs of the counters and a quantizer for bi-level-quantizing the output of the filter. It is thus possible to produce an image having a good quality free from deterioration due to the rapid switching of region judgements and bi-level-quantizing methods.
Inventors
- 👤 Takayoshi Semasa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 19:42
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/40062; H04N1/40075; H04N1/405; H04N1/4051; H04N1/4052; H04N1/4053
Claims Analysis
Total Claims: 52
Claim 1
Independent Claim
188 words
An image processing apparatus for inputting a multi-level image signal including a succession of pixels obtained by electrically scanning an image which contains letters, figures, photographs and screened-halftone in the form of a mixture and outputting the multi-level image signal, the image processing apparatus comprising: A) a screened-halftone pattern detecting circuit for detecting the screened-halftone pattern by using an image signal which represents a first vicinity of the image which contains a target pixel in the succession of pixels; B) a screened-halftone smoothing circuit responsive to the screened-halftone pattern detection state on each pixel in the succession of pixels; C) a continuous-tone pattern detecting circuit for judging whether or not the target pixel is in the continuous-tone region by using an image signal which represents a second vicinity of the image which contains the target pixel; D) a continuous-tone smoothing circuit responsive to the continuous-tone pattern detection state on each pixel in the succession of pixels; and E) a filter for filtering the image signal of the target pixel on the basis of characteristics in accordance with either or both of the outputs of the two smoothing circuits.
Claim 2
Dependent Claim
188 words
An image processing apparatus for inputting a multi-level image signal including a succession of pixels obtained by electrically scanning an image which contains letters, figures, photographs and screened-halftone in the form of a mixture and outputting the multi-level image signal, the image processing apparatus comprising: A) a screened-halftone pattern detecting circuit for detecting the screened-halftone pattern by using an image signal which represents a first vicinity of the image which contains a target pixel in the succession of pixels; B) a screened-halftone smoothing circuit responsive to the screened-halftone pattern detection state on each pixel in the succession of pixels; C) a continuous-tone pattern detecting circuit for judging whether or not the target pixel is in the continuous-tone region by using an image signal which represents a second vicinity of the image which contains the target pixel; D) a continuous-tone smoothing circuit responsive to the continuous-tone pattern detection state on each pixel in the succession of pixels; and E) a filter for filtering the image signal of the target pixel on the basis of characteristics in accordance with either or both of the outputs of the two smoothing circuits.
Claim 3
Dependent Claim
17 words
The apparatus of claim 1 further including a bi-level-quantizing circuit responsive to the output of the filter.
Claim 4
Dependent Claim
37 words
An image processing apparatus according to claim 2, wherein the bi-level-quantizing circuit includes a means for bi-level-quantizing the output with a fixed threshold and a means for bi-level-quantizing the output by using an ordered dither threshold matrix.
Claim 5
Dependent Claim
25 words
An image processing apparatus according to claim 2, wherein the bi-level-quantizing circuit includes a means for bi-level-quantizing the output by using an error diffusion method.
Claim 6
Dependent Claim
48 words
An image processing apparatus according to any of claims 1 to 3, wherein at least one of the circuits includes a region judging memory for temporarily storing the pattern detection state so that the smoothing circuit smoothes on the basis of the output of the region judging memory.
Claim 7
Dependent Claim
120 words
An image processing apparatus according to claim 1, wherein the screened-halftone pattern detecting circuit includes: a maximum luminance detector for obtaining the maximum luminance in a decision pixel block; a minimum luminance detector for obtaining the minimum luminance in the decision pixel block; an average luminance detector for obtaining the average luminance in the decision pixel block; a subtracter for obtaining the difference between the maximum luminance and the minimum luminance; a comparator for comparing the luminance of each pixel with the average luminance; a comparison result register for temporarily storing the output of the comparator; and a screened-halftone pattern detector for detecting a screened-halftone pattern from the output of the subtracter and the output of the comparison result register.
Claim 8
Dependent Claim
85 words
An image processing apparatus according to claim 1, wherein the continuous-tone pattern detecting circuit includes: a maximum luminance detector for obtaining the maximum luminance in a decision pixel block; a minimum luminance detector for obtaining the minimum luminance in the decision pixel block; a subtracter for obtaining the difference between the maximum luminance and the minimum luminance; and a continuous-tone pattern detector for detecting a continuous-tone pattern on the basis of the outputs of the maximum luminance detector, the minimum luminance detector and the subtracter.
Claim 9
Dependent Claim
66 words
An image processing apparatus according to claim 1, wherein the screened-halftone pattern detecting circuit and the continuous-tone pattern detecting circuit include in common a maximum luminance detector for obtaining the maximum luminance in a decision pixel block, a minimum luminance detector for obtaining the minimum luminance in the decision pixel block and a subtracter for obtaining the difference between the maximum luminance and the minimum luminance.
Claim 10
Dependent Claim
137 words
An image processing apparatus according to claim 2, wherein the bi-level-quantizing means includes; a register for storing a quantizing error with respect to a neighboring pixel; a weighting adder adding a predetermined weighting to a quantizing error; a multiplier for multiplying an addition signal by a predetermined coefficient of 0 to 1 in accordance with the control signal from a region judging an controlling circuit; an adder for adding the output of the weighting adder and the output of the multiplier; a quantizer for quantizing the output of the adder; a re-quantizer for converting the output of the quantizer into a different level; a subtracter for subtracting the output of the re-quantizer from the input of the quantizer so as to generate a quantizing error signal; and an error memory for temporarily storing the quantizing error signal.
Claim 11
Dependent Claim
12 words
The apparatus of claim 1 wherein the smoothing circuits are both counters.
Claim 12
Dependent Claim
148 words
An image processing method for processing a multi-level image signal including a succession of pixels obtained by electrically scanning an image which contains letters, figures, photographs and screened-halftone in the form of a mixture and outputting the multi-level image signal, the image processing method comprising: detecting the screened-halftone pattern using an image signal which represents a first vicinity of the image which contains a target pixel in the succession of pixels; smoothing the results of the step of detecting; judging whether or not the target pixel is in the continuous-tone region by using an image signal which represents a second vicinity of the image which contains the target pixel; smoothing the results of the step of judging; and filtering the image signal of the target pixel gradually on the basis of different characteristics in accordance with either or both of the results of the two steps of smoothing.
Claim 13
Dependent Claim
148 words
An image processing method for processing a multi-level image signal including a succession of pixels obtained by electrically scanning an image which contains letters, figures, photographs and screened-halftone in the form of a mixture and outputting the multi-level image signal, the image processing method comprising: detecting the screened-halftone pattern using an image signal which represents a first vicinity of the image which contains a target pixel in the succession of pixels; smoothing the results of the step of detecting; judging whether or not the target pixel is in the continuous-tone region by using an image signal which represents a second vicinity of the image which contains the target pixel; smoothing the results of the step of judging; and filtering the image signal of the target pixel gradually on the basis of different characteristics in accordance with either or both of the results of the two steps of smoothing.
Claim 14
Dependent Claim
18 words
The method of claim 11 further including the step of bi-level-quantizing the results of the step of filtering.
Claim 15
Dependent Claim
28 words
The method of claim 12, wherein the step of bi-level-quantizing includes bi-level-quantizing the results with a fixed threshold and bi-level-quantizing the results using an ordered dither threshold matrix.
Claim 16
Dependent Claim
19 words
The method of claim 12 wherein said step of bi-level-quantizing bi-level-quantizes the results by using an error diffusion method.
Claim 17
Dependent Claim
25 words
The method of any of claim 11 to 14, wherein the smoothing is performed on the basis of the output of a region judging memory.
Claim 18
Dependent Claim
83 words
The method of claim 11, wherein the step of detecting includes: obtaining the maximum luminance in a decision pixel block; obtaining the average luminance in the decision pixel block; obtaining the difference between the maximum luminance and the minimum luminance; comparing the luminance of each pixel with the average luminance; temporarily storing the results of the step of comprising; and detecting a screened-halftone pattern from the result of the step of obtaining the difference and the result of the step of temporarily storing.
Claim 19
Dependent Claim
78 words
The method of claim 11, wherein the step of judging includes: obtaining the maximum luminance in a decision pixel block; obtaining the minimum luminance in the decision pixel block; obtaining the difference between the maximum luminance and the minimum luminance; and detecting a continuous-tone pattern on the basis of the results of the step of obtaining the maximum and the results of the step of obtaining the minimum an the results of the step of obtaining the difference.
Claim 20
Dependent Claim
122 words
An image processing apparatus for inputting a multi-level image signal including a succession of pixels obtained by electrically scanning an image which contains letters, figures, photographs and screened-halftone in the form of a mixture and outputting the multi-level image signal, the image processing apparatus comprising: a screened-halftone pattern detecting circuit for detecting the screened-halftone pattern in the multi-level signal; a screened-halftone smoothing circuit responsive to the screened-halftone pattern detecting circuit; a continuous-tone pattern detecting circuit for detecting the continuous-tone pattern in the multi-level signal; a continuous-tone smoothing circuit responsive to the continuous-tone pattern detecting circuit; and a filter for filtering the image signal on the basis of characteristics in accordance with either or both of the outputs of the two smoothing circuits.
Claim 21
Dependent Claim
122 words
An image processing apparatus for inputting a multi-level image signal including a succession of pixels obtained by electrically scanning an image which contains letters, figures, photographs and screened-halftone in the form of a mixture and outputting the multi-level image signal, the image processing apparatus comprising: a screened-halftone pattern detecting circuit for detecting the screened-halftone pattern in the multi-level signal; a screened-halftone smoothing circuit responsive to the screened-halftone pattern detecting circuit; a continuous-tone pattern detecting circuit for detecting the continuous-tone pattern in the multi-level signal; a continuous-tone smoothing circuit responsive to the continuous-tone pattern detecting circuit; and a filter for filtering the image signal on the basis of characteristics in accordance with either or both of the outputs of the two smoothing circuits.
Claim 22
Dependent Claim
12 words
The apparatus of claim 18 wherein the smoothing circuits are both counters.
Claim 23
Dependent Claim
17 words
The apparatus of claim 18 further including a bi-level-quantizing circuit responsive to the output of the filter.
Claim 24
Dependent Claim
38 words
An image processing apparatus according to claim 20, wherein the bi-level quantizing circuit includes a means for bi-level-quantizing the output with a fixed threshold and a means for bi-level-quantizing the output by using an ordered dither threshold matrix.
Claim 25
Dependent Claim
25 words
An image processing apparatus according to claim 20, wherein the bi-level-quantizing circuit includes a means for bi-level-quantizing the output by using an error diffusion method.
Claim 26
Dependent Claim
137 words
An image processing apparatus according to claim 20, wherein the bi-level-quantizing circuit includes; a register for storing a quantizing error with respect to a neighboring pixel; a weighting adder adding a predetermined weighting to a quantizing error; a multiplier for multiplying an addition signal by a predetermined coefficient of 0 to 1 in accordance with the control signal from a region judging an controlling circuit; an adder for adding the output of the weighting adder and the output of the multiplier; a quantizer for quantizing the output of the adder; a re-quantizer for converting the output of the quantizer into a different level; a subtracter for subtracting the output of the re-quantizer from the input of the quantizer so as to generate a quantizing error signal; and an error memory for temporarily storing the quantizing error signal.
Claim 27
Dependent Claim
49 words
An image processing apparatus according to any of claims 18 to 23, wherein at least one of the smoothing circuits includes a region judging memory for temporarily storing the pattern detection state so that the smoothing circuit smoothes on the basis of the output of the region judging memory.
Claim 28
Dependent Claim
120 words
An image processing apparatus according to claim 18, wherein the screened-halftone pattern detecting circuit includes: a maximum luminance detector for obtaining the maximum luminance in a decision pixel block; a minimum luminance detector for obtaining the minimum luminance in the decision pixel block; an average luminance detector for obtaining the average luminance in the decision pixel block; a subtracter for obtaining the difference between the maximum luminance and the minimum luminance; a comparator for comparing the luminance of each pixel with the average luminance; a comparison result register for temporarily storing the output of the comparator; and a screened-halftone pattern detector for detecting a screened-halftone pattern from the output of the subtracter and the output of the comparison result register.
Claim 29
Dependent Claim
99 words
An image processing apparatus according to claim 18, wherein the continuous-tone pattern detecting circuit includes: a maximum luminance detector for obtaining the maximum luminance in a decision pixel block; a minimum luminance detector for obtaining the minimum luminance in the decision pixel block; an average luminance detector for obtaining the average luminance in the decision pixel block; a subtracter for obtaining the difference between the maximum luminance and the minimum luminance; and a continuous-tone pattern detector for detecting a continuous-tone pattern on the basis of the outputs of the maximum luminance detector, the minimum luminance detector and the subtracter.
Claim 30
Dependent Claim
66 words
An image processing apparatus according to claim 18, wherein the screened-halftone pattern detecting circuit and the continuous-tone pattern detecting circuit include in common a maximum luminance detector for obtaining the maximum luminance in a decision pixel block, a minimum luminance detector for obtaining the minimum luminance in the decision pixel block and a subtracter for obtaining the difference between the maximum luminance and the minimum luminance.
Claim 31
Dependent Claim
133 words
An image processing method for processing a multi-level image signal including a succession of pixels obtained by electrically scanning an image which contains letters, figures, photographs and screened-halftone in the form of a mixture and outputting the multi-level image signal, the image processing method comprising: generating a first signal indicating a likelihood that the multi-level image signal represents a screened-halftone region, generating a second signal indicating a likelihood that the multi-level image signal represents a continuous-tone region, processing the multi-level image signal using a plurality of methods simultaneously, adjusting a first of the methods in accordance with the first and second signals generated in each of the steps of generating, and adjusting a second of the methods in accordance with the first and second signals generated in each of the steps of generating.
Claim 32
Dependent Claim
133 words
An image processing method for processing a multi-level image signal including a succession of pixels obtained by electrically scanning an image which contains letters, figures, photographs and screened-halftone in the form of a mixture and outputting the multi-level image signal, the image processing method comprising: generating a first signal indicating a likelihood that the multi-level image signal represents a screened-halftone region, generating a second signal indicating a likelihood that the multi-level image signal represents a continuous-tone region, processing the multi-level image signal using a plurality of methods simultaneously, adjusting a first of the methods in accordance with the first and second signals generated in each of the steps of generating, and adjusting a second of the methods in accordance with the first and second signals generated in each of the steps of generating.
Claim 33
Dependent Claim
33 words
The method of claim 28 wherein the step of processing uses filtering as the first method and wherein the step of adjusting a first of the methods adjusts the characteristics of the filtering.
Claim 34
Dependent Claim
33 words
The method of claim 28 wherein the step of processing uses dithering as the first method and wherein the step of adjusting a first of the methods adjusts the amplitude of the dithering.
Claim 35
Dependent Claim
33 words
The method of claim 30 wherein the step of processing uses filtering as the second method and wherein the step of adjusting a second of the methods adjusts the characteristics of the filtering.
Claim 36
Dependent Claim
18 words
The method of claim 28 further including the step of bi-level-quantizing the results of the step of filtering.
Claim 37
Dependent Claim
28 words
The method of claim 32, wherein the step of bi-level-quantizing includes bi-level-quantizing the results with a fixed threshold and bi-level-quantizing the results using an ordered dither threshold matrix.
Claim 38
Dependent Claim
19 words
The method of claim 32 wherein said step of bi-level-quantizing bi-level-quantizes the results by using an error diffusion method.
Claim 39
Dependent Claim
25 words
The method of any of claim 28 to 34, wherein the smoothing is performed on the basis of the output of a region judging memory.
Claim 40
Dependent Claim
83 words
The method of claim 28, wherein the step of detecting includes: obtaining the maximum luminance in a decision pixel block; obtaining the average luminance in the decision pixel block; obtaining the difference between the maximum luminance and the minimum luminance; comparing the luminance of each pixel with the average luminance; temporarily storing the results of the step of comparing; and detecting a screened-halftone pattern from the result of the step of obtaining the difference and the result of the step of temporarily storing.
Claim 41
Dependent Claim
78 words
The method of claim 28, wherein the step of judging includes: obtaining the maximum luminance in a decision pixel block; obtaining the minimum luminance in the decision pixel block; obtaining the difference between the maximum luminance and the minimum luminance; and detecting a continuous-tone pattern on the basis of the results of the step of obtaining the maximum and the results of the step of obtaining the minimum and the results of the step of obtaining the difference.
Claim 42
Dependent Claim
179 words
An image processing apparatus for inputting a multi-level image signal including a succession of pixels obtained by electrically scanning an image which contains letters, figures, photographs and screened-halftone in the form of a mixture and outputting the multi-level image signal, the image processing apparatus comprising: screened-halftone pattern detecting means for detecting the screened-halftone pattern by using an image signal which represents a first vicinity of the image which contains a target pixel in the succession of pixels; screened-halftone smoothing means for smoothing the screened-halftone pattern detection state on each pixel in the succession of pixels; continuous-tone pattern detecting means for judging whether or not the target pixel is in the continuous-tone region by using an image signal which represents a second vicinity of the image which contains the target pixel; continuous-tone smoothing means for smoothing the continuous-tone pattern detection state on each pixel in the succession of pixels; and filtering means for filtering the image signal of the target pixel on the basis of characteristics in accordance with either or both of the outputs of the two smoothing means.
Claim 43
Dependent Claim
179 words
An image processing apparatus for inputting a multi-level image signal including a succession of pixels obtained by electrically scanning an image which contains letters, figures, photographs and screened-halftone in the form of a mixture and outputting the multi-level image signal, the image processing apparatus comprising: screened-halftone pattern detecting means for detecting the screened-halftone pattern by using an image signal which represents a first vicinity of the image which contains a target pixel in the succession of pixels; screened-halftone smoothing means for smoothing the screened-halftone pattern detection state on each pixel in the succession of pixels; continuous-tone pattern detecting means for judging whether or not the target pixel is in the continuous-tone region by using an image signal which represents a second vicinity of the image which contains the target pixel; continuous-tone smoothing means for smoothing the continuous-tone pattern detection state on each pixel in the succession of pixels; and filtering means for filtering the image signal of the target pixel on the basis of characteristics in accordance with either or both of the outputs of the two smoothing means.
Claim 44
Dependent Claim
13 words
The apparatus of claim 38 wherein the smoothing means are both counting means.
Claim 45
Dependent Claim
14 words
The apparatus of claim 38 further including bi-level-quantizing means responsive to the filtering means.
Claim 46
Dependent Claim
37 words
An image processing apparatus according to claim 40, wherein the bi-level-quantizing means includes a means for bi-level-quantizing the output with a fixed threshold and a means for bi-level-quantizing the output by using an ordered dither threshold matrix.
Claim 47
Dependent Claim
25 words
An image processing apparatus according to claim 40, wherein the bi-level-quantizing means includes a means for bi-level-quantizing the output by using an error diffusion method.
Claim 48
Dependent Claim
137 words
An image processing apparatus according to claim 40, wherein the bi-level-quantizing means includes; a register for storing a quantizing error with respect to a neighboring pixel; a weighting adder adding a predetermined weighting to a quantizing error; a multiplier for multiplying an addition signal by a predetermined coefficient of 0 to 1 in accordance with the control signal from a region judging an controlling circuit; an adder for adding the output of the weighting adder and the output of the multiplier; a quantizer for quantizing the output of the adder; a re-quantizer for converting the output of the quantizer into a different level; a subtracter for subtracting the output of the re-quantizer from the input of the quantizer so as to generate a quantizing error signal; and an error memory for temporarily storing the quantizing error signal.
Claim 49
Dependent Claim
51 words
An image processing apparatus according to any of claims 38 to 43, wherein at least one of the smoothing means includes a region judging memory means for temporarily storing the pattern detection state so that the smoothing means smoothes on the basis of the output of the region judging memory means.
Claim 50
Dependent Claim
120 words
An image processing apparatus according to claim 38, wherein the screened-halftone pattern detecting means includes: a maximum luminance detector for obtaining the maximum luminance in a decision pixel block; a minimum luminance detector for obtaining the minimum luminance in the decision pixel block; an average luminance detector for obtaining the average luminance in the decision pixel block; a subtracter for obtaining the difference between the maximum luminance and the minimum luminance; a comparator for comparing the luminance of each pixel with the average luminance; a comparison result register for temporarily storing the output of the comparator; and a screened-halftone pattern detector for detecting a screened-halftone pattern from the output of the subtracter and the output of the comparison result register.
Claim 51
Dependent Claim
99 words
An image processing apparatus according to claim 38, wherein the continuous-tone pattern detecting means includes: a maximum luminance detector for obtaining the maximum luminance in a decision pixel block; a minimum luminance detector for obtaining the minimum luminance in the decision pixel block; an average luminance detector for obtaining the average luminance in the decision pixel block; a subtracter for obtaining the difference between the maximum luminance and the minimum luminance; and a continuous-tone pattern detector for detecting a continuous-tone pattern on the basis of the outputs of the maximum luminance detector, the minimum luminance detector and the subtracter.
Claim 52
Dependent Claim
66 words
An image processing apparatus according to claim 38, wherein the screened-halftone pattern detecting means and the continuous-tone pattern detecting means include in common a maximum luminance detector for obtaining the maximum luminance in a decision pixel block, a minimum luminance detector for obtaining the minimum luminance in the decision pixel block and a subtracter for obtaining the difference between the maximum luminance and the minimum luminance.
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