Threshold matrix-employed error diffusion image conversion method
First Claim
1. A method for converting a continuous tone image into a pseudo-halftone image, the method comprising the steps of:
- preparing a threshold matrix which has several elements which are two-dimensionally arranged, each element defining one threshold valuereceiving data of a continuous tone image desired to be converted into a pseudo-halftone image, the continuous tone image having a plurality of pixels which are two-dimensionally arranged, each pixel having one density value; and
subjecting all the pixels of the continuous tone image to an error-distribution binary conversion process using the threshold matrix, to thereby convert the density values of the pixels into binary values while distributing generated errors to neighboring pixels,wherein the threshold matrix is prepared to define the threshold values which are determined according to a blue noise mask producing manner.
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Abstract
An input density for a subject pixel position (x, y) is retrieved in S230. A modified density value I'"'"'(x, y) is calculated in S240 based on the input density value I(x, y) and the error e(x, y) stored in the corresponding error buffer. Then, in S250, a discrimination value for the subject pixel position (x, y) is retrieved from the bilevel threshold value matrix Mat2( ) which is produced through the blue noise characteristic method. One of two threshold values is assigned to the retrieved discrimination value. Thus, a threshold value T is determined for the subject pixel (x, y). Then, an output density value O(x, y) is determined based on the modified density value I'"'"'(x, y) and the threshold value T in S260, S270, and S280. Then, an error value E(x,y) is calculated based on the output density value O(x, y) and the modified density value I'"'"'(x, y). The error value E(x,y) is distributed to the error buffer 16 in S300 dependently on the error distribution matrix Bat( ). The above-described process is performed onto all the pixels of the input image.
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Citations
60 Claims
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1. A method for converting a continuous tone image into a pseudo-halftone image, the method comprising the steps of:
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preparing a threshold matrix which has several elements which are two-dimensionally arranged, each element defining one threshold value receiving data of a continuous tone image desired to be converted into a pseudo-halftone image, the continuous tone image having a plurality of pixels which are two-dimensionally arranged, each pixel having one density value; and subjecting all the pixels of the continuous tone image to an error-distribution binary conversion process using the threshold matrix, to thereby convert the density values of the pixels into binary values while distributing generated errors to neighboring pixels, wherein the threshold matrix is prepared to define the threshold values which are determined according to a blue noise mask producing manner. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for converting a continuous tone image into a pseudo-halftone image, the method comprising the steps of:
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preparing a threshold matrix which has several elements which are two-dimensionally arranged, each element defining one threshold value; receiving data of a continuous tone image desired to be converted into a pseudo-halftone image, the continuous tone image having a plurality of pixels which are two-dimensionally arranged, each pixel having one density value; and subjecting all the pixels of the continuous tone image to an error-distribution binary conversion process using the threshold matrix, to thereby convert the density values of the pixels into binary values while distributing generated errors to neighboring pixels, wherein the threshold matrix preparing step includes the steps of; preparing a uniform density matrix provided with several elements which are arranged two-dimensionally and which have equal density values; subjecting all the elements of the uniform density matrix to an error-distribution binary conversion process to convert the density values of the elements into binary values while distributing generated errors to neighboring elements, thereby producing a binary value matrix based on the binary values produced for at least a part of all the elements; and producing the threshold matrix based on the binary values located at least within a part of the binary value matrix. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A method for converting a continuous tone image into a pseudo-halftone image, the method comprising the steps of:
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preparing a threshold matrix which has several elements which are two-dimensionally arranged, each element defining one threshold value; receiving data of a continuous tone image desired to be converted into a pseudo-halftone image, the continuous tone image having a plurality of pixels which are two-dimensionally arranged, each pixel having one density value; and subjecting all the pixels of the continuous tone image to an error-distribution binary conversion process using the threshold matrix, to thereby convert the density values of the pixels into binary values while distributing generated errors to neighboring pixels, wherein the threshold matrix preparing step includes the steps of; storing, into a storage device, discrimination values indicative of the threshold values defined for all the elements in the threshold matrix, data amount of each discrimination value being smaller than that of a corresponding threshold value; and producing a threshold value for each element position based on a discrimination value read from the storage device at a corresponding position. - View Dependent Claims (30, 31, 32, 33, 34)
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35. A method for converting a continuous tone image into a pseudo-halftone image, the method comprising the steps of:
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preparing a threshold matrix which has several elements which are two-dimensionally arranged, each element defining one threshold value; receiving data of a continuous tone image desired to be converted into a pseudo-halftone image, the continuous tone image having a plurality of pixels which are two-dimensionally arranged, each pixel having one density value; and subjecting all the pixels of the continuous tone image to an error-distribution binary conversion process using the threshold matrix, to thereby convert the density values of the pixels into binary values while distributing generated errors to neighboring pixels, wherein each pixel of the continuous tone image has a density in a range defined between a lowest density value S and a highest density value L, where S is equal to or higher than zero, and L is higher than S, and wherein the threshold matrix preparing step prepares the threshold matrix so that n kinds of different threshold values are distributed in the threshold matrix where n is an integer in a range from two to the total number of the elements, the n kinds of threshold values including at least a first threshold value H1 and a second threshold value H2, the first threshold value H2 being higher than the first threshold value H1, the number of the elements having the first threshold value H1 and the number of the elements having the second threshold value H2 being higher than those of elements having each of other threshold values, a sum T of the first and second threshold values H1 and H2 satisfying an inequality T>
L. - View Dependent Claims (36, 37, 38, 39, 40, 41, 42, 43)
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44. A method for converting a continuous tone image into a pseudo-halftone image, the method comprising the steps of:
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preparing a threshold matrix which has several elements which are two-dimensionally arranged, each element defining one threshold value; receiving data of a continuous tone image desired to be converted into a pseudo-halftone image, the continuous tone image having a plurality of pixels which are two-dimensionally arranged, each pixel having one density value; and subjecting all the pixels of the continuous tone image to an error-distribution binary conversion process using the threshold matrix, to thereby convert the density values of the pixels into binary values while distributing generated errors to neighboring pixels, wherein the threshold matrix preparing step prepares the threshold matrix so that n different threshold values are distributed in the threshold matrix where n is an integer in a range from two to the total number of the elements, the numbers of elements having the respective different threshold values being different from one another. - View Dependent Claims (45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55)
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56. A data recording medium for storing data of a program for converting a continuous tone image into a pseudo-halftone image, the program comprising:
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a program for preparing a threshold matrix which has several elements which are two-dimensionally arranged, each element defining one threshold value; a program for receiving data of a continuous tone image desired to be converted into a pseudo-halftone image, the continuous tone image having a plurality of pixels which are two-dimensionally arranged, each pixel having one density value; and a program for subjecting all the pixels of the continuous tone image to an error-distribution binary conversion process using the threshold matrix, to thereby convert the density values of the pixels into binary values while distributing generated errors to neighboring pixels, wherein the threshold matrix is prepared to define the threshold values which are determined according to a blue noise mask producing manner.
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57. A data recording medium for storing data of a program for converting a continuous tone image into a pseudo-halftone image, the program comprising:
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a program of preparing a threshold matrix which has several elements which are two-dimensionally arranged, each element defining one threshold value; a program of receiving data of a continuous tone image desired to be converted into a pseudo-halftone image, the continuous tone image having a plurality of pixels which are two-dimensionally arranged, each pixel having one density value; and a program of subjecting all the pixels of the continuous tone image to an error-distribution binary conversion process using the threshold matrix, to thereby convert the density values of the pixels into binary values while distributing generated errors to neighboring pixels; wherein the threshold matrix preparing program includes; a program of preparing a uniform density matrix provided with several elements which are arranged two-dimensionally and which have equal density values; a program of subjecting all the elements of the uniform density matrix to an error-distribution binary conversion process to convert the density values of the elements into binary values while distributing generated errors to neighboring elements, thereby producing a binary value matrix based on the binary values produced for at least a part of all the elements; and a program of producing the threshold matrix based on the binary values located at least within a part of the binary value matrix.
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58. A data recording medium for storing data of a program for converting a continuous tone image into a pseudo-halftone image, the program comprising:
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a program of preparing a threshold matrix which has several elements which are two-dimensionally arranged, each element defining one threshold value; a program of receiving data of a continuous tone image desired to be converted into a pseudo-halftone image, the continuous tone image having a plurality of pixels which are two-dimensionally arranged, each pixel having one density value; and a program of subjecting all the pixels of the continuous tone image to an error-distribution binary conversion process using the threshold matrix, to thereby convert the density values of the pixels into binary values while distributing generated errors to neighboring pixels; wherein the threshold matrix preparing program includes; a program of storing, into a storage device, discrimination values indicative of the threshold values defined for all the elements in the threshold matrix, data amount of each discrimination value being smaller than that of a corresponding threshold value; and a program of producing a threshold value for each element position based on a discrimination value read from the storage device at a corresponding position.
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59. A data recording medium for storing data of a program for converting a continuous tone image into a pseudo-halftone image, the program comprising:
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a program of preparing a threshold matrix which has several elements which are two-dimensionally arranged, each element defining one threshold value; a program of receiving data of a continuous tone image desired to be converted into a pseudo-halftone image, the continuous tone image having a plurality of pixels which are two-dimensionally arranged, each pixel having one density value; and a program of subjecting all the pixels of the continuous tone image to an error-distribution binary conversion process using the threshold matrix, to thereby convert the density values of the pixels into binary values while distributing generated errors to neighboring pixels, wherein each pixel of the continuous tone image has a density in a range defined between a lowest density value S and a highest density value L, where S is equal to or higher than zero, and L is higher than S, and wherein the threshold matrix preparing program prepares the threshold matrix so that n kinds of different threshold values are distributed in the threshold matrix where n is an integer in a range from two to the total number of the elements, the n kinds of threshold values including at least a first threshold value H1 and a second threshold value H2, the first threshold value H2 being higher than the first threshold value H1, the number of the elements having the first threshold value H1 and the number of the elements having the second threshold value H2 being higher than those of elements having each of other threshold values, a sum T of the first and second threshold values H1 and H2 satisfying an inequality T>
L.
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60. A data recording medium for storing data of a program for converting a continuous tone image into a pseudo-halftone image, the program comprising:
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a program of preparing a threshold matrix which has several elements which are two-dimensionally arranged, each element defining one threshold value; a program of receiving data of a continuous tone image desired to be converted into a pseudo-halftone image, the continuous tone image having a plurality of pixels which are two-dimensionally arranged, each pixel having one density value; and a program of subjecting all the pixels of the continuous tone image to an error-distribution binary conversion process using the threshold matrix, to thereby convert the density values of the pixels into binary values while distributing generated errors to neighboring pixels, wherein the threshold matrix preparing program prepares the threshold matrix so that n different threshold values are distributed in the threshold matrix where n is an integer in a range from two to the total number of the elements, the numbers of elements having the respective different threshold values being different from one another.
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Specification