Detection of non-uniform spatial scaling of an image
First Claim
Patent Images
1. A method of detecting non-uniform spatial scaling of an image in a particular direction, the method comprising:
- dividing, by an active image process executing on a programmable apparatus, the image into regions;
deriving for at least two of the regions a directional measure of spatial frequency energy in the particular direction; and
comparing, by the programmable apparatus, said respective directional measures of spatial frequency energy in the particular direction for at least two of the regions to detect non-uniform spatial scaling in the particular direction;
wherein a directional measure of total spatial frequency energy is evaluated in the particular direction for at least two of the regions anda measure of non-uniform spatial scaling is derived from a ratio of two said directional measures of total spatial frequency energy evaluated over two respective regions or groups of regions;
where the particular direction is horizontal, the regions into which the image is divided comprise an image middle region and two image side regions respectively disposed on opposite horizontal sides of the image middle region and the ratio is the ratio of the horizontal directional measure of total spatial frequency energy evaluated over the image middle image region to the horizontal directional measure of total spatial frequency energy evaluated over the two image side regions.
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Abstract
To detect non-uniform spatial scaling of an image in the horizontal direction (for example in 4:3 to 16:9 aspect ratio conversion) the image is divided into regions, for example a middle region and two side regions. A measure of horizontal spatial frequency energy is taken in each region by for example subtracting the values of horizontally adjacent pixels and a comparison is made between measures of horizontal spatial frequency energy for the different regions.
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Citations
12 Claims
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1. A method of detecting non-uniform spatial scaling of an image in a particular direction, the method comprising:
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dividing, by an active image process executing on a programmable apparatus, the image into regions; deriving for at least two of the regions a directional measure of spatial frequency energy in the particular direction; and comparing, by the programmable apparatus, said respective directional measures of spatial frequency energy in the particular direction for at least two of the regions to detect non-uniform spatial scaling in the particular direction; wherein a directional measure of total spatial frequency energy is evaluated in the particular direction for at least two of the regions and a measure of non-uniform spatial scaling is derived from a ratio of two said directional measures of total spatial frequency energy evaluated over two respective regions or groups of regions; where the particular direction is horizontal, the regions into which the image is divided comprise an image middle region and two image side regions respectively disposed on opposite horizontal sides of the image middle region and the ratio is the ratio of the horizontal directional measure of total spatial frequency energy evaluated over the image middle image region to the horizontal directional measure of total spatial frequency energy evaluated over the two image side regions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An apparatus for detecting non-uniform spatial scaling of an image in a particular direction, the apparatus comprising:
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an active image detector dividing the image into regions; a plurality of energy measurement units providing a directional measure of total spatial frequency energy; and a plurality of comparators for evaluating directional spatial frequency energy totals for at least two of the regions; wherein a measure of non-uniform spatial scaling is derived from a ratio of two directional spatial frequency energy totals evaluated over two respective regions or groups of regions, wherein the directional spatial frequency energy totals are normalised by dividing them by respective other directional or non-directional spatial frequency energy totals; wherein the division is by a directional spatial frequency energy total evaluated orthogonally to the particular direction. - View Dependent Claims (10, 11)
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12. An apparatus for detecting non-uniform spatial scaling of an image in a particular direction, the apparatus comprising:
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an active image detector dividing the image into regions; a plurality of energy measurement units providing a directional measure of total spatial frequency energy; and a plurality of comparators for evaluating directional spatial frequency energy totals for at least two of the regions; wherein a measure of non-uniform spatial scaling is derived from a ratio of two directional spatial frequency energy totals evaluated over two respective regions or groups of regions, wherein the particular direction is horizontal, the regions into which the image is divided comprise an image middle region and two image side regions respectively disposed on opposite horizontal sides of the image middle region and the ratio is the ratio of the horizontal spatial frequency energy evaluated over the image middle image region to the total horizontal spatial frequency energy evaluated over the two image side regions.
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Specification