DETECTION OF NON-UNIFORM SPATIAL SCALING OF AN IMAGE

• US 20100316297A1
• Filed: 05/24/2010
• Published: 12/16/2010
• Est. Priority Date: 06/11/2009
• Status: Active Grant

• Current Assignee: Grass Valley USA Incorporated
• Original Assignee: Snell Limited (Belden Inc.)
• Inventors: Knee, Michael James
• Granted Patent: US 8,855,443 B2
• Time in Patent Office: Days
• US Class Current: 382/191
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/20021 Dividing image into blocks, subimages or windows
• CPC Class Codes: G06T 2207/30168 Image quality inspection
• CPC Class Codes: G06T 7/0002 Inspection of images, e.g. flaw detection
• CPC Class Codes: G06T 7/44 using image operators, e.g. filters, edge density metrics or local histograms
• CPC Class Codes: H04N 5/21 Circuitry for suppressing or minimising disturbance, e.g. moiré or halo
• CPC Class Codes: H04N 7/0122 the input and the output signals having different aspect ratios

Abstract

Systems and methods 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 and a comparison is made between measures of horizontal spatial frequency energy for the different regions

Claims

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; and

comparing, by the programmable apparatus executing a plurality of energy measurement functions, respective directional measures of spatial frequency energy in the particular direction for at least two of the regions.

2. A method according to claim 1, wherein a directional measure of total spatial frequency energy is evaluated in the direction for at least two of the regions and 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.

3. A method according to claim 1 where the directional spatial frequency energy totals are normalised by dividing them by respective other directional or non-directional spatial frequency energy totals.

4. A method according to claim 2 where the division is by a directional spatial frequency energy total evaluated orthogonally to the direction.

5. A method according to claim 1 where the measures of directional spatial frequency energy are sums of magnitudes of differences between the values of adjacent pixels that represent the image.

6. A method according to claim 1 where the measures of directional spatial frequency energy are sums of squares of differences between the values of adjacent pixels that represent the image.

7. A method according to claim 4 where the pixel values are luminance values.

8. A method according to claim 5 where the pixel values are luminance values.

9. A method according to claim 1 where the direction is horizontal and the ratio is the ratio of the horizontal spatial frequency energy evaluated over an image middle image region to the total horizontal spatial frequency energy evaluated over two image side regions.

10. A method according to any claim 1 in which the results from the analysis of a plurality of images from a sequence of related images are combined.

11. An apparatus for detecting non-uniform spatial scaling of an image in a particular direction, the apparatus comprising:

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.

12. An apparatus according to claim 11, wherein the directional spatial frequency energy totals are normalised by dividing them by respective other directional or non-directional spatial frequency energy totals.

13. An apparatus according to claim 12, wherein the division is by a directional spatial frequency energy total evaluated orthogonally to the direction.

14. An apparatus according to claim 11, wherein the measures of directional spatial frequency energy are sums of magnitudes of differences between the values of adjacent pixels that represent the image.

15. An apparatus according claim 11, wherein the measures of directional spatial frequency energy are sums of squares of differences between the values of adjacent pixels that represent the image.

16. An apparatus according to claim 11, wherein the direction is horizontal and the ratio is the ratio of the horizontal spatial frequency energy evaluated over an image middle image region to the total horizontal spatial frequency energy evaluated over two image side regions.

17. A non-transitory computer readable medium containing instructions adapted to cause a programmable apparatus to implement a method of detecting non-uniform spatial scaling of an image in a particular direction, the method comprising:

dividing the image into regions; and

comparing respective directional measures of spatial frequency energy in the direction for at least two of the regions.