Digital polarization filter

• US 20040052424A1
• Filed: 06/27/2003
• Published: 03/18/2004
• Est. Priority Date: 12/29/2000
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Nik Software, Inc. (Alphabet Inc.)
• Inventors: Kokemohr, Nils
• Granted Patent: US 7,257,269 B2
• Time in Patent Office: Days
• US Class Current: 382/254
• 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 1/60 Colour correction or control H04N1/54 takes precedence

Abstract

A method for simulating in a digital image the effect of a physical polarization filter is described, the digital image having a plurality of pixels (50) with color, by darkening (54) each of the plurality of pixels (52) having a cool color and lightening (56) each of the plurality of pixels having a warm color. Optional adjustment algorithms are disclosed, including a contrast adjustment (62), saturation adjustment (64) and intensity adjustment.

Claims

1. A method for simulating in a digital image the effect of a polarization filter, the digital image having a plurality of pixels each with a color temperature, comprising the step of darkening each of the plurality of pixels having a cool color temperature as a function of that color temperature.

2. The method of claim 1, further comprising the step of lightening each of the plurality of pixels having a warm color temperature as a function of that color temperature.

3. The method of claim 1, further comprising the step of applying one or more than one adjustment algorithm chosen from the group consisting of contrast adjustment, saturation adjustment, and intensity adjustment.

20. The method of claims 1 or 6, further comprising the step of applying one or more than one adjustment algorithm chosen from the group consisting of contrast adjustment and saturation adjustment.

4. A method for simulating in a digital image the effect of a polarization filter, the digital image having a plurality of pixels each with a color temperature, comprising steps for darkening each of the plurality of pixels having a cool color temperature as a function of that color temperature and lightening each of the plurality of pixels having a warm color temperature as a function of that color temperature.

5. A method for simulating in a digital image the effect of a polarization filter at a rotation angle θ

, comprising the steps of;

(a) storing the digital image in a first memory, the digital image comprising a plurality of pixels each having a pixel luminance and a color temperature;

(b) transforming each of the plurality of pixels by changing the pixel luminance as a function of the rotation angle θ and

the color temperature; and

(c) storing each of the transformed pixels into a second memory.

6. The method of claim 5, wherein the transforming step further comprises decreasing the pixel luminance of pixels having cool color temperature as a function of that color temperature and increasing the pixel luminance of pixels having warm color temperature as a function of that color temperature.

7. The method of claim 6, further comprising the step of adjusting the transformation by applying one or more than one adjustment algorithm chosen from the group consisting of contrast adjustment saturation adjustment, and intensity adjustment.

8. A method for simulating in a digital image the effect of a polarization filter at a rotation angle θ

, comprising the steps of;

(a) storing an RGB copy of the digital image in a first memory, the digital image comprising a plurality of pixels each having a first pixel luminance and color channel luminances comprising a first red channel luminance, a first green channel luminance, and a first blue channel luminance;

(b) transforming one or more than one of the color channel luminances of each of the plurality of pixels, the transformation comprising the steps of;

(1) calculating a second pixel luminance from the first red channel luminance;

(2) calculating an angle weighted pixel luminance from the first pixel luminance, the second pixel luminance, and rotation angle θ

, and

(3) calculating a second blue channel luminance from the angle weighted pixel luminance, the first pixel luminance, and the first blue channel luminance; and

(c) storing in a second memory, for each of the plurality of pixels, the color channel luminances including the one or more than one transformed color channel luminances.

9. The method of claim 8 wherein the second pixel luminance is an average of the color channel luminances.

10. The method of claim 8 wherein the transforming step further comprises the steps of transforming the first green channel luminance of each of the plurality of pixels by calculating a second green channel luminance from the angle weighted pixel luminance, the first pixel luminance, and the first green channel luminance;

and transforming the first red channel luminance of each of the plurality of pixels by calculating a second red channel luminance from the angle weighted pixel luminance, the first pixel luminance, and the first red channel luminance.

11. The method of claim 8, wherein the step of calculating an angle weighted pixel luminance comprises the formula b″

=1/90*((90−

|q−

90|)*h′

+|q−

90|*h), where h″

is the angle weighted pixel luminance, h′

is the second pixel luminance and q is expressed in degrees ranging from 0 to 180.

12. The method of claim 8, wherein tie step of calculating a second blue channel luminance comprises the formula p,b=([Ixy,b*h″

/h]+Ixy,b+[h″

−

h])/2, where p,b is the second blue channel luminance, h″

is the angle weighted pixel luminance, h is the first pixel luminance, and Ixy,b is the first blue channel luminance.

13. The method of claim 8, further comprising the step of adjusting the transformation of the color channel luminances by applying one or more than one algorithm chosen from the group consisting of contrast adjustment, saturation adjustment, and intensity adjustment.

14. A computer readable medium having contents for causing a computer-based information handling system to perform steps for simulating in a digital image the effect of a polarization filter at a rotation angle θ

, the steps comprising;

(a) storing the digital image in a first memory, the digital image comprising a plurality of pixels each having a pixel luminance and a red channel luminance, a green channel luminance, and a blue channel luminance;

(b) transforming each of the plurality of pixels by changing the pixel luminance as a function of the rotation angle θ and

the red channel luminance; and

(c) storing each of the transformed pixels into a second memory.

15. A computer readable medium having contents for causing a computer-based information handling system to perform steps for simulating in a digital image the effect of a polarization filter at a rotation angle θ

, the steps comprising;

(a) storing an RGB copy of the digital image in a first memory, the digital image comprising a plurality of pixels each having a first pixel luminance and color channel luminances comprising a first red channel luminance, a first green channel luminance, and a first blue channel luminance;

(b) transforming one or more than one of the color channel luminances of each of the plurality of pixels, the transformation comprising the steps of;

(1) calculating a second pixel luminance from the first red channel luminance;

(2) calculating an angle weighted pixel luminance from the first pixel luminance, the second pixel luminance, and rotation angle θ

, and

(3) calculating a second blue channel luminance from the angle weighted pixel luminance, the first pixel luminance, and the first blue channel luminance; and

(c) storing in a second memory, for each of the plurality of pixels, the color channel luminances including the one or more than one transformed color channel luminances.

16. A computer readable medium having contents for causing a computer-based information handling system to perform steps for simulating in a digital image the effect of a polarization filter, the digital image having a plurality of pixels each with a color temperature, comprising the step of darkening each of the plurality of pixels having a cool color temperature as a function of that color temperature.

17. A computer readable medium having contents for causing a digital camera system to perform steps for simulating in a digital image the effect of a polarization filter, the digital image having a plurality of pixels with color each with a color temperature, comprising the step of darkening each of the plurality of pixels having a cool color temperature as a function of that color temperature.

18. A digital polarizing filter for simulating in a digital image the effect of a polarization filter at a rotation angle θ

, the digital image having a plurality of pixels with color each with a color temperature, comprising;

a processor,

a memory in communication with the processor, and

a computer readable medium in communication with the processor, the computer readable medium having contents for causing the processor to perform the step of darkening each of the plurality of pixels having a cool color temperature as a function of that color temperature.

19. The digital polarizing filter of claim 18, further comprising a computer readable medium having contents for causing the processor to perform the step of lightening each of the plurality of pixels having a warm color temperature as a function of that color temperature.