Image processing method and apparatus

• US 8,155,468 B2
• Filed: 06/13/2011
• Issued: 04/10/2012
• Est. Priority Date: 01/18/2008
• Status: Expired due to Fees

• Current Assignee: FotoNation Limited (Adeia Inc.)
• Original Assignee: DigitalOptics Corporation Europe Limited (Adeia Inc.)
• Inventors: Albu, Felix, Drimbarean, Alexandru, Zamfir, Adrian, Florea, Corneliu
• Primary Examiner(s): Bhatnagar, Anand
• Assistant Examiner(s): TSAI, TSUNG YIN
• Application Number:
  US13/159,296
• Publication Number:
  US 20110243439A1
• Time in Patent Office: 302 Days
• Field of Search: None
• US Class Current: 382/260
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 2207/20012 Locally adaptive
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/94 based on local image properties, e.g. for local contrast enhancement
• CPC Class Codes: H04N 1/56 Processing of colour picture signals H04N1/52 takes precedence
• CPC Class Codes: H04N 1/60 Colour correction or control H04N1/54 takes precedence

Abstract

A method of processing an image includes traversing pixels of an image in a single pass over the image. An inverting function is applied to the pixels. A recursive filter is applied to the inverted pixel values. The filter has parameters which are derived from previously traversed pixel values of the image. A pixel value is combined with a filter parameter for the pixel to provide a processed pixel value for a processed image.

Claims

1. A method of processing an RGB format image comprising:

traversing each pixel of the image in a single pass over the image;

applying an inverting function to a combination of each color plane value for a pixel;

applying a recursive filter to each inverted pixel value, said filter having parameters which are derived from previously traversed pixel values of said image; and

combining said pixel value with said filter parameter for said pixel to provide a pixel value for a processed image

wherein said recursive filter parameters H(i,j) comprise;

H(i,j)=α

H(i,j−

1)+(1−

α

) (f(G(i,j,k)))

where;

α

comprises the pole of the filter;

G(i,j,k) comprises the pixel value for the respective red (R), green (G) or blue (B) color plane k; and

f(G(i,j,k)) comprises said inverting function.

3. A method according to claim 1 or 2 wherein said traversing is one of:

row wise;

column wise;

or traversing any path across the image.

4. A method according to claim 1 further comprising:

providing (20) an estimate of the average of the red, green and blue planes from previously traversed pixel values of said image;

providing (25) correction terms for one or more of said planes, said correction terms being dependent on said color channel average estimates; and

wherein said combining (50) includes multiplying a pixel value with a correction term.

5. A method according to claim 1 wherein said combining comprises one of a linear or a logarithmic combination.

6. A method according to claim 5 wherein said combining comprises multiplying said pixel value, a correction term and said filter parameter for said pixel to provide a pixel value for a processed image.

7. A method according to claim 4 wherein said providing an estimate of the average of said red, green and blue channels comprises:

R=β

·

R+(1−

β

)·

G(i,j,1)

G=β

·

G+(1−

β

)·

G(i,j,2)

B=β

·

B+(1−

β

)·

G(i,j,3),

where;

β

comprises a coefficient between 0 and 1.

8. A method according to claim 4 wherein said correction terms γ

_R,γ

_B for each of said red and blue color planes comprise;

9. A method according to claim 1 wherein said inverting function is:

11. A method according to claim 4 wherein combining comprises:

G₁(i,j,1)=G(i,j,1)·

H(i,j)·

γ

_R

G₁(i,j,2)=G(i,j,2)·

H(i,j)

G₁(i,j,3)=G(i,j,3)·

H(i,j)·

γ

_B

where;

γ

_R,γ

_B comprise said correction terms.

12. A method according to claim 4 wherein combining comprises:

16. A method according to claim 1 or claim 2, comprising iteratively applying steps a) to d) to one or more successively processed images each of steps b), c) and d) being respectively adapted to improve one of image luminance or image sharpness.

17. An image processing apparatus comprising:

one or more optics and a sensor for acquiring a digital image;

a processor; and

one or more storage media having digital code embodied therein for programming the processor to perform an image processing method comprising;

acquiring the image;

using the processor to perform the method of claim 1 or claim 2.

18. One or more computer-readable media having code embedded therein for programming a processor to perform a method of processing an image, wherein the method comprises:

acquiring the image;

using the processor to perform the method of claim 1 or claim 2.

2. A method of processing a YCC format image comprising:

traversing each pixel of the image in a single pass over the image;

applying an inverting function to an intensity value for each pixel;

applying a recursive filter to each inverted pixel value, said filter having parameters which are derived from previously traversed pixel values of said image; and

combining said pixel value with said filter parameter for said pixel to provide a pixel value for a processed image

wherein said recursive filter parameters H(i,j) comprise;

H(i,j)=α

H(i,j−

1)+(1−

α

)(f(Y(i,j)))

where;

α

comprises the pole of the IIR filter;

Y(i,j) comprises said pixel intensity value; and

f(Y(i,j)) comprises said inverting function.

10. A method according to claim 2 wherein said inverting function is:

13. A method according to claim 2 wherein said inverting function is:

14. A method according to claim 2 wherein said combining comprises:

Y₁(i,j)=Y(i,j)[1+ε

(i,j)·

(1−

H(i,j))]

where;

ε

(i,j) comprises a gain factor.

15. A method according to claim 14 wherein ε

(i,j) comprises a constant or varies for said image.