Suppressing flicker in digital images

• US 8,934,030 B2
• Filed: 02/20/2013
• Issued: 01/13/2015
• Est. Priority Date: 02/20/2013
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.), Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.), Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Inventors: Kim, Minwoong, Allebach, Jan P., Bengtson, Kurt Robert
• Primary Examiner(s): Berhan, Ahmed A
• Application Number:
  US13/771,991
• Publication Number:
  US 20140232902A1
• Time in Patent Office: 692 Days
• Field of Search: 348/222.1, 348/220.1, 348/221.1, 348/226.1, 348/227.1, 348/228.1, 348/229.1, 348/230.1, 348/362, 348/272
• US Class Current: 348/226.1
• CPC Class Codes: H04N 1/409 Edge or detail enhancement; Noise or error suppression
• CPC Class Codes: H04N 1/4092 Edge or detail enhancement
• CPC Class Codes: H04N 1/58 Edge or detail enhancement; Noise or error suppression, e.g. colour misregistration correction H04N1/62 takes precedence
• CPC Class Codes: H04N 23/745 Detection of flicker frequency or suppression of flicker wherein the flicker is caused by illumination, e.g. due to fluorescent tube illumination or pulsed LED illumination

Abstract

Suppressing flicker in digital images includes deriving pixel values from a non-content area of a digital image, estimating flicker values within the non-content area, and suppressing flicker throughout the digital image based on the estimated flicker values of the non-content area.

Claims

1. A method of suppressing flicker in digital images, comprising:

deriving pixel values from a non-content area of a digital image;

estimating flicker values within said non-content area; and

suppressing flicker throughout said digital image based on said estimated flicker values of said non-content area

wherein;

estimating said flicker values within said non-content area includes analyzing each color channel of said pixel values individually,

estimating said flicker values within said non-content area includes determining average pixel value curves that map said pixel values averaged along a direction perpendicular to said flicker within said non-content area for each of said color channels,

estimating said flicker values within said non-content area includes identifying local maximums and local minimums of said average pixel value curve,

estimating said flicker values within said non-content area includes interpolating an undistorted pixel values curve formed with connecting midpoints between said local maximums and local minimums.

2. The method of claim 1, wherein said non-content area comprises a constant color reflectance.

3. The method of claim 1, wherein estimating said flicker values within said non-content area includes estimating flicker values with ratios between said average pixel value curve and said undistorted pixel curve.

4. The method of claim 1, wherein suppressing said flicker throughout said digital image based on said estimated flicker values of said non-content area includes adjusting said pixel values across an entire row based on said estimated flicker where said entire row comprises a common flicker value and spans both a non-content area and a content area of said digital image.

5. A system for suppressing flicker in digital images, comprising:

a photographing engine to make digital images of objects placed on a platen;

a pixel value engine to derive pixel values from a non-content area of said digital images;

an estimating engine to estimate flicker values within said non-content area;

a suppressing engine to suppress said flicker throughout said digital image based on said estimated flicker values of said non-content area;

an average pixel value curve engine to determine an average pixel value curve that depicts said pixel values of said non-content area;

a local extremity engine to determine coordinates of said average pixel value curve that estimate a product of said flicker values and undistorted pixel values; and

an interpolation engine to determine an undistorted pixel value curve that depicts said undistorted pixel values of said non-content area.

6. The system of claim 5, wherein said non-content area comprises a constant color reflectance.

7. The system of claim 5, wherein said estimating engine estimates said flicker values with ratios between said average pixel value curve and said undistorted pixel value curve.

8. A computer program product for suppressing flicker in digital images, comprising:

a non-transitory computer readable storage medium, said non-transitory computer readable storage medium comprising computer readable program code embodied therewith, said computer readable program code comprising program instructions that, when executed, causes a processor to;

make a digital image;

derive pixel values from a non-content area of said digital image;

determine an average pixel value curve that depicts said pixel values of said non-content area;

determine coordinates of said average pixel value curve that estimate a product of said flicker values and undistorted pixel values;

determine an undistorted pixel value curve that depicts said undistorted pixel values of said non-content area; and

estimate flicker values within said non-content area with ratios between said average pixel value curve and said undistorted pixel value curve.

9. The computer program product of claim 8, further comprising computer readable program code comprising program instructions that, when executed, causes said processor to suppress said flicker throughout said digital image based on said estimated flicker values of said non-content area.

10. The computer program product of claim 8, wherein said non-content area comprises a constant color reflectance.

11. The computer program product of claim 8, wherein the average pixel value curve maps said pixel values averaged along a direction perpendicular to said flicker within said non-content area.