CORRECTING DEFECTS IN AN IMAGE

• US 20110044558A1
• Filed: 08/17/2010
• Published: 02/24/2011
• Est. Priority Date: 08/21/2009
• Status: Active Grant

• Current Assignee: Grass Valley USA Incorporated
• Original Assignee: Snell Limited (Belden Inc.)
• Inventors: Clédière, Sébastien
• Granted Patent: US 8,515,204 B2
• Time in Patent Office: Days
• US Class Current: 382/275
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/20012 Locally adaptive
• CPC Class Codes: G06T 5/005 Retouching; Inpainting; Scratch removal detecting, correction, reducing or removing defects, e.g. non-responsive pixels of solid state image sensors H04N25/68, scratch removal for cinematographic films scanned by electronic image sensor H04N5/253
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/77 Retouching; Inpainting; Scratch removal
• CPC Class Codes: H04N 5/253 Picture signal generating by scanning motion picture films or slide opaques, e.g. for telecine scanning details therefor H04N3/36 ; standard conversion therefor H04N7/0112

Abstract

A method of correcting dirt or other defects in video or other images in which a region is provisionally corrected, an accumulated gradient measure formed along the periphery of the region with and without correction and the region corrected or not depending on a comparison of the gradient measures.

Claims

1. A method of correcting defects in a representation of an image, using an image processor, comprising the steps in the image processor of identifying the periphery of said region;

evaluating a gradient at locations at the periphery;

forming an accumulated gradient measure along the periphery and controlling the application of an image correction process to that region in accordance with the accumulated gradient measure.

2. A method according to claim 1 in which the said measure is evaluated for a corrected image region and for the same region of the same image without correction and the application of correction to that region is controlled by the result of a comparison between the said measure with and without correction.

3. A method according to claim 2 in which the said image correction process is inhibited in regions where the said gradient measure for a corrected image would be higher than the said measure for the same region in the uncorrected image.

4. A method according to claim 1 in which the said gradient measure is a sum along the periphery of pixel value magnitude differences between pixels at the edge of the said region and respective adjacent pixels outside the said region.

5. A method according to claim 1 in which the said correction process is a process that corrects artefacts due to film dirt.

6. Apparatus for correcting defects in a representation of an image, the apparatus comprising an image correction unit receiving an image input;

a periphery analysis unit for identifying the periphery of a region of the image which has been corrected in the image correction unit and for evaluating a periphery gradient measure for said region with and without correction, in which the application of correction to that region in an image output is controlled by the result of a comparison between the said measure with correction and the said measure without correction.

7. Apparatus according to claim 6 in which the said image correction unit is inhibited in regions where the said gradient measure for a corrected image would be higher than the said measure for the same region in the uncorrected image.

8. Apparatus according to claim 6 in which the said gradient measure is a sum along the periphery of pixel value magnitude differences between pixels at the edge of the said region and respective adjacent pixels outside the said region.

9. Apparatus according to claim 6 in which the said correction process is a process that corrects artefacts due to film dirt.

10. A computer program product comprising instructions adapted to cause programmable apparatus to implement a method comprising the steps of provisionally correcting a region of an image to remove dirt or other defect;

evaluating an accumulated gradient measure along the periphery of the region with and without correction; and

choosing whether or not to use the corrected region depending on a comparison of the gradient measures.