Image processing apparatus
First Claim
1. An image processing apparatus which, for an input two-dimensional image constructed by arraying, in a matrix, a number of pixels each representing a luminance value at a corresponding position, adjusts a spatial frequency characteristic on the basis of a desired spatial frequency adjustment filter characteristic, and compresses the image, comprising:
- a spatial filter for obtaining a new luminance value of each pixel of an input image on the basis of a first coefficient having a first filter characteristic which forms the desired spatial frequency adjustment filter characteristic in cooperation with a second filter characteristic, thereby generating a two-dimensional intermediate image which has the adjusted spatial frequency characteristic of the input image; and
an orthogonal transform section for performing two-dimensional orthogonal transform for the intermediate image on the basis of a second coefficient which has the second filter characteristic, which forms the desired spatial frequency adjustment filter characteristic in cooperation with the first filter characteristic, and is used for two-dimensional orthogonal transform for compressing the intermediate image generated by said spatial filter, thereby generating image data which has the adjusted spatial frequency characteristic of the intermediate image and has undergone two-dimensional orthogonal transform for image compression, wherein said orthogonal transform section segments the intermediate image generated by said spatial filter into a plurality of second regions each constructed by N×
N pixels (N is an integer;
N≧
2), and performs two-dimensional orthogonal transform in units of second regions using N×
N second coefficients having the second filter characteristic, thereby generating the image data which has the adjusted spatial frequency characteristic of the intermediate image and has undergone two-dimensional orthogonal transform for image compression;
wherein said orthogonal transform section is operative to segment the intermediate image generated by said spatial filter into a plurality of second regions each constructed by N×
N pixels (N is an integer, N≧
2), and to perform two-dimensional orthogonal transform in units of second regions using N×
N second coefficients having the second filter characteristic, thereby generating the image data which has the adjusted spatial frequency characteristic of the intermediate image and has undergone two-dimensional orthogonal transform for image compression; and
wherein as the second coefficients, N×
N coefficients obtained by individually multiplying or adding N×
N filter coefficients for adjusting the spatial frequency characteristic of the intermediate image and N×
N transform coefficients used for two-dimensional orthogonal transform of the intermediate image are used.
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Abstract
An image processing apparatus includes a spatial filter and orthogonal transform section. The spatial filter obtains a new luminance value of each pixel of an input image on the basis of a first coefficient having a first filter characteristic which forms the desired spatial frequency adjustment filter characteristic in cooperation with a second filter characteristic, thereby generating a two-dimensional intermediate image which has the adjusted spatial frequency characteristic of the input image. The orthogonal transform section performs two-dimensional orthogonal transform for the intermediate image on the basis of a second coefficient which has the second filter characteristic, which forms the desired spatial frequency adjustment filter characteristic in cooperation with the first filter characteristic, and is used for two-dimensional orthogonal transform for compressing the intermediate image generated by the spatial filter, thereby generating image data which has the adjusted spatial frequency characteristic of the intermediate image and has undergone two-dimensional orthogonal transform for image compression.
18 Citations
17 Claims
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1. An image processing apparatus which, for an input two-dimensional image constructed by arraying, in a matrix, a number of pixels each representing a luminance value at a corresponding position, adjusts a spatial frequency characteristic on the basis of a desired spatial frequency adjustment filter characteristic, and compresses the image, comprising:
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a spatial filter for obtaining a new luminance value of each pixel of an input image on the basis of a first coefficient having a first filter characteristic which forms the desired spatial frequency adjustment filter characteristic in cooperation with a second filter characteristic, thereby generating a two-dimensional intermediate image which has the adjusted spatial frequency characteristic of the input image; and
an orthogonal transform section for performing two-dimensional orthogonal transform for the intermediate image on the basis of a second coefficient which has the second filter characteristic, which forms the desired spatial frequency adjustment filter characteristic in cooperation with the first filter characteristic, and is used for two-dimensional orthogonal transform for compressing the intermediate image generated by said spatial filter, thereby generating image data which has the adjusted spatial frequency characteristic of the intermediate image and has undergone two-dimensional orthogonal transform for image compression, wherein said orthogonal transform section segments the intermediate image generated by said spatial filter into a plurality of second regions each constructed by N×
N pixels (N is an integer;
N≧
2), and performs two-dimensional orthogonal transform in units of second regions using N×
N second coefficients having the second filter characteristic, thereby generating the image data which has the adjusted spatial frequency characteristic of the intermediate image and has undergone two-dimensional orthogonal transform for image compression;
wherein said orthogonal transform section is operative to segment the intermediate image generated by said spatial filter into a plurality of second regions each constructed by N×
N pixels (N is an integer, N≧
2), and to perform two-dimensional orthogonal transform in units of second regions using N×
N second coefficients having the second filter characteristic, thereby generating the image data which has the adjusted spatial frequency characteristic of the intermediate image and has undergone two-dimensional orthogonal transform for image compression; and
wherein as the second coefficients, N×
N coefficients obtained by individually multiplying or adding N×
N filter coefficients for adjusting the spatial frequency characteristic of the intermediate image and N×
N transform coefficients used for two-dimensional orthogonal transform of the intermediate image are used.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 14, 15, 16, 17)
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6. An apparatus according to claim 2, wherein said spatial filter adjusts the spatial frequency characteristic of the input image using, of the plurality of first coefficients having different spatial frequency characteristics, a first coefficient selected on the basis of a predetermined statistic amount calculated from the luminance values of the pixels contained in the first region.
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7. An apparatus according to claim 1, wherein said orthogonal transform section performs two-dimensional orthogonal transform for adjustment of the spatial frequency characteristic of the intermediate image and image compression by two-dimensional orthogonal transform using, of the plurality of second coefficients having different spatial frequency characteristics, a second coefficient selected on the basis of a predetermined statistic amount calculated from the luminance values of the pixels contained in the second region.
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8. An apparatus according to claim 6, wherein as the statistic amount, an average luminance of the pixels in each region, the difference between the luminance value of the central pixel and the average luminance of the pixels in each region, the difference between the luminance value of the central pixel and a value obtained by multiplying a pixel in each region by a predetermined coefficient, or the difference between the luminance value of the central pixel and the luminance value of the farthest pixel in each region is used.
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14. An apparatus according to claim 1, wherein as the first filter characteristic for emphasizing intermediate- to high-frequency portions of the spatial frequency characteristic is used.
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15. An apparatus according to claim 14, wherein as the second filter characterstic, a characteristic for attenuating a high-frequency portion of the spatial frequency characteristic is used.
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16. An apparatus according to claim 2, wherein the first filter characteristics having different spatial frequency characteristics are individually used for a luminance signal and color difference signals.
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17. An apparatus according to claim 2, wherein the second filter characteristics having different spatial frequency characteristics are individually used for a luminance signal and color difference signals.
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9. An image processing apparatus which, for an input two-dimensional image constructed by arraying, in a matrix, a number of pixels each representing a luminance value at a corresponding position, adjusts a spatial frequency characteristic on the basis of a desired spatial frequency adjustment filter characteristic, and compresses the image, comprising:
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a spatial filter for obtaining a new luminance value of each pixel of an input image on the basis of a first coefficient having a first filter characteristic which forms the desired spatial frequency adjustment filter characteristic in cooperation with a second filter characteristic, thereby generating a two-dimensional intermediate image which has the adjusted spatial frequency characteristic of the input image; and
an orthogonal transform section for performing two-dimensional orthogonal transform for the intermediate image on the basis of a second coefficient which has the second filter characteristic, which forms the desired spatial frequency adjustment filter characteristic in cooperation with the first filter characteristic, and is used for two-dimensional orthogonal transform for compressing the intermediate image generated by said spatial filter thereby generating image data which has the adjusted spatial frequency characteristic of the intermediate image and has undergone two-dimensional orthogonal transform for image compression, wherein said orthogonal transform section segments the intermediate image generated by said spatial filter into a plurality of second regions each constructed by N×
N pixels (N is an integer;
N≧
2), and performs two-dimensional orthogonal transform in units of second regions using N×
N second coefficients having the second filter characteristic, thereby generating the image data which has the adjusted spatial frequency characteristic of the intermediate image and has undergone two-dimensional orthogonal transform for image compression;
wherein said orthogonal transform section segments the intermediate image generated by said spatial filter into a plurality of second regions each constructed by N×
N pixels (N is an integer;
N≧
2), and performs two-dimensional orthogonal transform in units of second regions using N×
N second coefficients having the second filter characteristic, thereby generating the image data which has the adjusted spatial frequency characteristic of the intermediate image and has undergone two-dimensional orthogonal transform for image compression; and
wherein as the statistic amount, an average luminance of the pixels in each region, the difference between the luminance value of the central pixel and the average luminance of the pixels in each region, the difference between the luminance value of the central pixel and a value obtained by multiplying a pixel in each region by a predetermined coefficient, or the difference between the luminance value of the central pixel and the luminance value of the farthest pixel in each region is used.
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10. An image processing apparatus which, for an input two-dimensional image constructed by arraying, in a matrix, a number of pixels each representing a luminance value at a corresponding position, adjusts a spatial frequency characteristic on the basis of a desired spatial frequency adjustment filter characteristic, and compresses the image, comprising:
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a spatial filter for obtaining a new luminance value of each pixel of an input image on the basis of a first coefficient having a first filter characteristic which forms the desired spatial frequency adjustment filter characteristic in cooperation with a second filter characteristic, thereby generating a two-dimensional intermediate image which has the adjusted spatial frequency characteristic of the input image; and
an orthogonal transform section for performing two-dimensional orthogonal transform for the intermediate image on the basis of a second coefficient which has the second filter characteristic, which forms the desired spatial frequency adjustment filter characteristic in cooperation with the first filter characteristic, and is used for two-dimensional orthogonal transform for compressing the intermediate image generated by said spatial filter, thereby generating image data which has the adjusted spatial frequency characteristic of the intermediate image and has undergone two-dimensional orthogonal transform for image compression, wherein said orthogonal transform section segments the intermediate image generated by said spatial filter into a plurality of second regions each constructed by N×
N pixels (N is an integer;
N≧
2), and performs two-dimensional orthogonal transform in units of second regions using N×
N second coefficients having the second filter characteristic, thereby generating the image data which has the adjusted spatial frequency characteristic of the intermediate image and has undergone two-dimensional orthogonal transform for image compression;
wherein the first coefficients comprise a central coefficient having a positive coefficient value corresponding to a central pixel as an arbitrary pixel in a first region having M×
M pixels (M is an odd number;
M≧
3) and (M×
M−
1) peripheral coefficients corresponding to peripheral pixels formed from pixels in the first region except the central pixel in the input image formed from a number of pixels two-dimensionally arrayed along directions i and j perpendicular to each other, each peripheral coefficient having a negative coefficient value,said spatial filter has a pipeline processing section comprising;
a plurality of block adders for calculating and outputting a sum of luminance values of pixels belonging to an individual block in units of predetermined blocks each constructed by at least one of the M pixels parallelly received from the input image;
a plurality of shift registers provided in correspondence with said block adders to sequentially shift outputs from said block adders in synchronism with a predetermined clock signal by a predetermined number of stages, and hold and output the outputs;
an adder for selectively totalizing predetermined output values of output values from said block adders and output values from said shift registers to output a value obtained by totalizing (M×
M−
1) products of the luminance values of the individual peripheral pixels of the M×
M pixels in the first region and absolute values of the peripheral coefficients corresponding to the peripheral pixels;
a peripheral multiplier for multiplying an output from said totalizer by −
1;
a central multiplier for multiplying the luminance value of the central pixel, which is held by one of said shift registers, by the central coefficient and outputting the value;
an adder for adding an output from said central multiplier to an output from said peripheral multiplier and outputting a sum value; and
a divider for dividing the output from said adder to output a new luminance value of the central pixel, and the two-dimensional intermediate image having the adjusted spatial frequency characteristic of the input image is obtained by scanning the pixels on the input image one by one in an i direction and one by one in a j direction in synchronism with a predetermined clock signal to parallelly receive M pixels arrayed adjacent along the j direction by said pipeline processing section and sequentially calculating the new luminance value of the central pixel of the received M×
M pixels.- View Dependent Claims (11, 12, 13)
said central multiplier bit-shifts the luminance value of the central pixel in an upper bit direction by the power value of 2 forming the central coefficient, thereby calculating and outputting the product of the luminance value of the central pixel and the central coefficient. -
12. An apparatus according to claim 10, the central coefficient of the first coefficient is a sum of a plurality of power values of 2,
said central multiplier comprises a plurality of multipliers parallelly arranged in correspondence with the power values of 2 forming the central coefficient, and each multiplier bit-shifts the luminance value of the central pixel in the upper bit direction by the corresponding power value of 2, thereby calculating and outputting the product of the luminance value of the central pixel and the central coefficient. -
13. An apparatus according to claim 10, wherein the central coefficient and the peripheral coefficients of the first coefficient are set such that a sum of the central coefficient and a total sum of the peripheral coefficients has a power value of 2, and
said divider divides the output from said adder by bit-shifting the output from said adder in a lower bit direction by the power value of 2 representing the sum of the central coefficient and the total sum of the peripheral coefficients.
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Specification