Color correction involving color phase detection and phase-dependent control

• US 20070153019A1
• Filed: 01/05/2006
• Published: 07/05/2007
• Est. Priority Date: 01/05/2006
• Status: Active Grant

• Current Assignee: Xueshan Technologies Inc. (Wi-LAN Inc.)
• Original Assignee: NuCORE Technology, Inc. (MediaTek, Inc.)
• Inventors: Nakasone, Youichi, Sasai, Toshihiro
• Granted Patent: US 7,643,681 B2
• Time in Patent Office: Days
• US Class Current: 345/589
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: H04N 1/60 Colour correction or control H04N1/54 takes precedence
• CPC Class Codes: H04N 1/6005 with luminance or chrominance signals, e.g. LC1C2, HSL or YUV
• CPC Class Codes: H04N 1/6075 Corrections to the hue

Abstract

Color correction is performed on a first set of three pixel values by determining a color phase of the pixel values. The determined color phase is used to determine a phase difference, and the phase difference is used to control an amount of color phase rotation applied to the chrominance pixel values of the first set. The color phase is also used to determine a first gain, and the first gain is used to control a scaling of the rotated chrominance pixel values, thereby generating color corrected chrominance pixel values. The color phase is also used to determine a second gain, and the second gain is used to control an amount of scaling applied to the luminance pixel value of the first set, thereby generating the color corrected luminance pixel value. How color phase determines phase difference, the first gain and the second gain is changed depending on lighting conditions.

Claims

1. An integrated circuit that processes a first set of YCbCr pixel values, the first set comprising a first Y luminance value, a first Cb chrominance value, and a first Cr chrominance value, the integrated circuit generating a second set of YCbCr pixel values, the second set comprising a second Y lumuninance value, a second Cb chrominance value, and a second Cr chrominance value, the integrated circuit comprising:

a color phase adjust circuit that receives the first Cb chrominance value and the first Cr chrominance value and that performs color phase rotation based on a relationship between the first Cb chrominance value and the first Cr chrominance value, the color phase adjust circuit outputting an intermediate Cb chrominance value and an intermediate Cr chrominance value;

a chrominance adjust circuit that receives the intermediate Cb chrominance value and the intermediate Cr chrominance value and that performs scaling based on the relationship between the first Cb chrominance value and the first Cr chrominance value, the chrominance adjust circuit outputting the second Cb chrominance value and the second Cr chrominance value; and

a luminance adjust circuit that receives the first Y luminance value and that performs scaling based on the relationship between the first Cb chrominance value and the first Cr chrominance value, the luminance adjust circuit outputting the second Y luminance value.

2. The integrated circuit of claim 1, further comprising:

a circuit that receives the first Cb chrominance value and the first Cr chrominance value and that outputs a number indicative of the relationship between the first Cb chrominance value and the first Cr chrominance value, wherein the circuit supplies the number to the color phase adjust circuit, the chrominance adjust circuit and the luminance adjust circuit.

3. The integrated circuit of claim 2, wherein the color phase adjust circuit comprises:

a portion that converts the number into a phase difference value; and

a portion that uses the phase difference value to convert the first Cb chrominance value and the first Cr chrominance value into the intermediate Cb chrominance value and the intermediate Cr chrominance value.

4. The integrated circuit of claim 3, wherein the portion that converts the number into the phase difference value comprises a lookup-table memory.

5. The integrated circuit of claim 1, further comprising:

an RGB-to-YCbCr conversion circuit that receives a set of RGB pixel values and that outputs the first set of YCbCr pixel values.

6. The integrated circuit of claim 5, further comprising:

a Bayer-to-RGB conversion circuit that receives Bayer values and outputs the set of RGB pixel values.

7. The integrated circuit of claim 6, wherein the integrated circuit is part of an image capture device, the image capture device comprising an image sensor, the image sensor outputting the Bayer values.

8. The integrated circuit of claim 7, wherein the image sensor comprises an analog front end/timing generator (AFE/TG) device and one of a charge coupled sensor (CCD) device and a CMOS sensor device.

9. The integrated circuit of claim 2, wherein the chrominance adjust circuit comprises:

a portion that converts the number into a gain value; and

a portion that uses the gain value to scale the intermediate Cb chrominance value into the second Cb chrominance value and to scale the intermediate Cr chrominance value into the second Cr chrominance value.

10. The integrated circuit of claim 9, wherein the portion that converts the number into the gain value comprises a lookup-table memory.

11. The integrated circuit of claim 1, wherein the relationship between the first Cb chrominance value and the first Cr chrominance value is a phase angle.

12. The integrated circuit of claim 1, wherein the relationship between the first Cb chrominance value and the first Cr chrominance value is a ratio of the first Cb chrominance value to the first Cr chrominance value.

13. The integrated circuit of claim 1, wherein the integrated circuit is part of an image capture device, the image capture device comprising an image sensor, the image sensor outputting image data that is converted into the first set of YCbCr pixel values.

14. A method, comprising:

(a) using an image sensor to capture an image and to output image data, wherein the image sensor is part of an image capture device, the image capture device being taken from the group consisting of;

a digital camera, a mobile communication device that includes a digital camera functionality;

(b) converting the image data into a set of YCbCr image pixel values, the set of YCbCr image pixel values including a first Y luminance value, a first Cb chrominance value and a first Cr chrominance value;

(c) using the first Cb chrominance value and the first Cr chrominance value to determine a phase angle; and

(d) using the phase angle to control a color adjust rotation operation, the color phase adjust operation converting the first Cb chrominance value and the first Cr chrominance value into an intermediate Cb chrominance value and an intermediate Cr chrominance value.

15. The method of claim 14, wherein the image capture device is operable in one of at least three light condition settings, wherein when the image capture device is in a first of the light condition settings then the phase angle is used in (d) in a first manner to control the color phase adjust operation, wherein when the image capture device is in a second of the light condition settings then the phase angle is used in (d) in a second manner to control the color phase adjust operation, and wherein when the image capture device is in a third of the light condition settings then the phase angle is used in (d) in a third manner to control the color phase adjust operation.

16. The method of claim 14, further comprising:

(e) using the phase angle to control a chrominance adjust operation, the chrominance adjust operation converting the intermediate Cb chrominance value and the intermediate Cr chrominance value into second Cb chrominance value and a second Cr chrominance value.

17. The method of claim 14, wherein the color adjust rotation operation comprises the steps of:

converting the phase angle into a phase difference; and

using the phase difference to adjust a color phase of the first Cb chrominance value and the first Cr chrominance value, the intermediate Cb chrominance value and the intermediate Cr chrominance value being a result of the color phase adjustment.

18. The method of claim 17, wherein the converting of the phase angle into a phase difference involves using the phase angle to look up the phase difference in a lookup table memory.

19. An image capture device, comprising:

a sensor portion that captures an image and outputs corresponding pixel information; and

means for receiving the pixel information from the sensor portion and for performing color correction on the pixel information by determining a color phase of the pixel information, and then by using the color phase to control a color phase rotation operation that converts the pixel information received from the sensor portion into phase rotated pixel information.

20. The circuit of claim 19, wherein the color correction also involves using the color phase to control a chrominance gain operation, the chrominance gain operation converting the phase rotated pixel information into color corrected pixel information.

21. The circuit of claim 20, wherein the color correction also involves using the color phase to control a luminance gain operation, the luminance gain operation converting a luminance value of the pixel information received by the means into a luminance value of the color corrected pixel information.

22. The circuit of claim 19, wherein the sensor portion comprises an image sensor that outputs Bayer data, and wherein the pixel information received by the means is YCbCr pixel information.