Method for automatic detection and correction of halo artifacts in images
First Claim
1. A method of detecting halo artifacts in an image, the method comprising:
- a. determining a first two-dimensional gradient field for an image, wherein the first gradient field includes a plurality of first gradient vectors, one first gradient vector associated with each pixel in the image;
b. determining a second two-dimensional gradient field for the processed image, wherein the second gradient field includes a plurality of second gradient vectors, one second gradient vector associated with each pixel in the processed image, wherein a first pixel in the image corresponds to a first pixel in the processed image;
c. calculating a gradient angle for each pixel, wherein a first gradient angle is an angle between a first gradient vector and a second gradient vector associated with the first pixel; and
d. calculating a relative angle for each pixel, wherein a first relative angle for the first pixel is the minimum between the first gradient angle and 360 degrees minus the first gradient angle.
1 Assignment
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Accused Products
Abstract
A method of automatically detecting and correcting halo artifacts within a processed image is described. The method computes a two-dimensional (2D) gradient field of the original image and a 2D gradient field of the processed image. Each gradient field includes a gradient vector corresponding to each pixel. To detect halo artifacts, the gradient vector at each pixel of the original image is compared to the gradient vector at the corresponding pixel of the processed image. A halo artifact is determined to exist at a given pixel if a direction of the two corresponding gradient vectors differs by at least a specified threshold. To correct the halo artifacts, a composite gradient field is generated using one of three correction methods. A final image is generated by integrating the newly generated composite gradient field using known integration methods from a 2D gradient field such as ones based on the Fast Fourier Transform.
43 Citations
42 Claims
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1. A method of detecting halo artifacts in an image, the method comprising:
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a. determining a first two-dimensional gradient field for an image, wherein the first gradient field includes a plurality of first gradient vectors, one first gradient vector associated with each pixel in the image; b. determining a second two-dimensional gradient field for the processed image, wherein the second gradient field includes a plurality of second gradient vectors, one second gradient vector associated with each pixel in the processed image, wherein a first pixel in the image corresponds to a first pixel in the processed image; c. calculating a gradient angle for each pixel, wherein a first gradient angle is an angle between a first gradient vector and a second gradient vector associated with the first pixel; and d. calculating a relative angle for each pixel, wherein a first relative angle for the first pixel is the minimum between the first gradient angle and 360 degrees minus the first gradient angle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of correcting halo artifacts in an image, the method comprising:
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a. determining a first two-dimensional gradient field for an image, wherein the first gradient field includes a plurality of first gradient vectors, each first gradient vector includes a first magnitude and a first direction; b. determining a second two-dimensional gradient field for the processed image, wherein the second gradient field includes a plurality of second gradient vectors, each second gradient vector includes a second magnitude and a second direction, further wherein each second gradient vector corresponds to a specific first gradient vector, thereby forming a first gradient vector and second gradient vector pair; c. generating a third two-dimensional gradient field, wherein the third gradient field includes a plurality of third gradient vectors, each third gradient vector corresponds to a specific first gradient vector and second gradient vector pair, and each third gradient vector includes a third magnitude equal to the second magnitude of the corresponding second gradient vector and a third direction equal to the first direction of the corresponding first gradient vector; and d. integrating the third gradient field thereby generating a corrected image. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A method of detecting and correcting halo artifacts in an image, the method comprising:
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a. determining a first two-dimensional gradient field for an image, wherein the first gradient field includes a plurality of first gradient vectors, each first gradient vector includes a first magnitude and a first direction; b. determining a second two-dimensional gradient field for the processed image, wherein the second gradient field includes a plurality of second gradient vectors, each second gradient vector includes a second magnitude and a second direction; c. quantifying a halo artifact value at each pixel; d. generating a third two-dimensional gradient field, wherein the third gradient field includes a plurality of third gradient vectors, each third gradient vector includes a third magnitude and a third direction, further wherein if the halo artifact value at a given pixel is less than a predetermined value, then the third magnitude equals the second magnitude and the third direction equals the second direction at the given pixel, and if the halo artifact value at the given pixel is greater than or equal to the predetermined value, then the third magnitude equals the second magnitude and the third direction equals the first direction at the given pixel; and e. integrating the third gradient field thereby generating a corrected image. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A method of detecting and correcting halo artifacts in an image, the method comprising:
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a. determining a first two-dimensional gradient field for an image, wherein the first gradient field includes a plurality of first gradient vectors, each first gradient vector includes a first magnitude and a first direction; b. determining a second two-dimensional gradient field for the processed image, wherein the second gradient field includes a plurality of second gradient vectors, each second gradient vector includes a second magnitude and a second direction; c. quantifying a halo artifact value at each pixel; d. generating a third two-dimensional gradient field, wherein the third gradient field includes a plurality of third gradient vectors, each third gradient vector includes a third magnitude and a third direction, further wherein if the halo artifact value at a given pixel is less than a predetermined value, then the third magnitude equals the second magnitude and the third direction equals the first direction at the given pixel, and if the halo artifact value at the given pixel is greater than or equal to the predetermined value, then the third magnitude equals the first magnitude and the third direction equals the first direction at the given pixel; and e. integrating the third gradient field thereby generating a corrected image. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. An apparatus for detecting halo artifacts in an image, the apparatus comprising:
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a. an application for; i. determining a first two-dimensional gradient field for an image, wherein the first gradient field includes a plurality of first gradient vectors, each first gradient vector includes a first magnitude and a first direction; ii. determining a second two-dimensional gradient field for the processed image, wherein the second gradient field includes a plurality of second gradient vectors, each second gradient vector includes a second magnitude and a second direction; iii. quantifying a halo artifact value at each pixel; iv. generating a third two-dimensional gradient field, wherein the third gradient field includes a plurality of third gradient vectors, each third gradient vector includes a third magnitude and a third direction, further wherein if the halo artifact value at a given pixel is less than a predetermined value, then the third magnitude equals the second magnitude and the third direction equals the second direction at the given pixel, and if the halo artifact value at the given pixel is greater than or equal to the predetermined value, then the third magnitude equals the second magnitude and the third direction equals the first direction at the given pixel; and v. integrating the third gradient field thereby generating a corrected image; and b. a processor configured for executing the application; and c. a memory coupled to the processor, the memory configured for temporarily storing data for execution by the processor.
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41. An apparatus for correcting halo artifacts in an image, the apparatus comprising:
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a. an application for; i. determining a first two-dimensional gradient field for an image, wherein the first gradient field includes a plurality of first gradient vectors, each first gradient vector includes a first magnitude and a first direction; ii. determining a second two-dimensional gradient field for the processed image, wherein the second gradient field includes a plurality of second gradient vectors, each second gradient vector includes a second magnitude and a second direction, further wherein each second gradient vector corresponds to a specific first gradient vector, thereby forming a first gradient vector and second gradient vector pair; iii. generating a third two-dimensional gradient field, wherein the third gradient field includes a plurality of third gradient vectors, each third gradient vector corresponds to a specific first gradient vector and second gradient vector pair, and each third gradient vector includes a third magnitude equal to the second magnitude of the corresponding second gradient vector and a third direction equal to the first direction of the corresponding first gradient vector; and iv. integrating the third gradient field thereby generating a corrected image; and b. a processor configured for executing the application; and c. a memory coupled to the processor, the memory configured for temporarily storing data for execution by the processor.
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42. An apparatus for detecting halo artifacts in an image, the apparatus comprising:
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a. an application for; i. determining a first two-dimensional gradient field for an image, wherein the first gradient field includes a plurality of first gradient vectors, each first gradient vector includes a first magnitude and a first direction; ii. determining a second two-dimensional gradient field for the processed image, wherein the second gradient field includes a plurality of second gradient vectors, each second gradient vector includes a second magnitude and a second direction; iii. quantifying a halo artifact value at each pixel; iv. generating a third two-dimensional gradient field, wherein the third gradient field includes a plurality of third gradient vectors, each third gradient vector includes a third magnitude and a third direction, further wherein if the halo artifact value at a given pixel is less than a predetermined value, then the third magnitude equals the second magnitude and the third direction equals the first direction at the given pixel, and if the halo artifact value at the given pixel is greater than or equal to the predetermined value, then the third magnitude equals the first magnitude and the third direction equals the first direction at the given pixel; and v. integrating the third gradient field thereby generating a corrected image; and b. a processor configured for executing the application; and c. a memory coupled to the processor, the memory configured for temporarily storing data for execution by the processor.
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Specification