Median computation-based integrated color interpolation and color space conversion methodology from 8-bit bayer pattern RGB color space to 12-bit YCrCb color space

• US 6,356,276 B1
• Filed: 03/18/1998
• Issued: 03/12/2002
• Est. Priority Date: 03/18/1998
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Acharya, Tinku
• Primary Examiner(s): Nguyen, Chanh
• Assistant Examiner(s): Alphonse, Fritz
• Application Number:
  US09/040,806
• Time in Patent Office: 1,455 Days
• Field of Search: 345/431, 345/153, 345/138, 345/150, 345/152, 345/154, 345/155, 345/427, 345/589, 345/600, 345/604, 345/606, 348/273, 348/242, 348/394, 348/220, 382/166
• US Class Current: 345/600
• CPC Class Codes: G06T 3/4015 Image demosaicing, e.g. colour filter arrays [CFA] or Bayer patterns
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values
• CPC Class Codes: H04N 25/134 based on three different wavelength filter elements

Abstract

An integrated color interpolation and color space conversion technique and apparatus. A raw image that is arranged in a Bayer pattern where each pixel has only one of the color components needed to form a full color resolution pixel may be converted using this technique directly to a YCrCb image space without any intermediate conversion or interpolation steps. Specifically, in one instance, an 8-bit Bayer pattern raw image may be converted directly to a 12-bit YCrCb space in a single step approach. Such an integrated technique may more readily and inexpensively implemented in hardware such as on a digital camera, or in software.

Claims

1. A method for converting pixels of an image, wherein each of the pixels has at least one color value, into a luminance and a chrominance color space comprising the steps of:

determining a position of each of the pixels in the image as a row position and a column position;

for each of the pixels, determining a luminance value for a specific pixel using the color values for pixels, in the neighborhood of the specific pixel;

for a subset of each of the pixels, determining a chrominance value for a specific subset pixel using the color values for pixels in the neighborhood of the specific subset pixel and applying a different operation depending upon the row position of the pixel; and

mapping the luminance and chrominance values into a luminance and chrominance color space.

2. A method according to claim 1 wherein the pixels of the image consist of raw image pixels.

3. A method according to claim 1 wherein the pixels of the image are arranged in a Bayer pattern.

4. A method according to claim 1 wherein the neighborhood of a pixel includes the pixel.

5. A method according to claim 1 wherein the neighborhood of a pixel includes pixels positioned no more than one row or column position away from the pixel.

6. A method according to claim 1 wherein determining a luminance value includes applying a different operation depending upon the row position of the pixel.

7. A method according to claim 6 wherein each of the pixels has either a red, green or blue color value and wherein determining a luminance value for a pixel location having a red color value includes determining a median of the green color values in the neighborhood of the red pixel, determining a median of the blue color values in the neighborhood of the red pixel, weighting the medians and the color value of the red pixel and adding the weighted medians and red color value to obtain the luminance.

8. A method according to claim 6 wherein each of the pixels has either a red, green or blue color value and wherein determining a luminance value for a pixel location having a blue color value includes determining a median of the green color values in the neighborhood of the blue pixel, determining a median of the red color values in the neighborhood of the blue pixel, weighting the medians and the blue color value for the blue pixel and adding the weighted medians and blue color value to obtain the luminance.

9. A method according to claim 1 wherein each of the pixels has either a red, green or blue color value and wherein determining a chrominance value for a pixel location having a green color value includes determining a median of the green color values in the neighborhood of the green pixel, determining a median of the blue color values in the neighborhood of the green pixel, determining a median of the red color values in the neighborhood of the green pixel, weighting the medians and adding the weighted medians to obtain the chrominance.

10. A method according to claim 9 wherein the subset of each of the pixel values excludes each of the pixels that does not have an odd row number position and an odd column number position so that only a Y component is generated for all other pixels in the luminance and chrominance color space.

11. A method according to claim 1, wherein for each pixel having an odd-numbered row and column position, determining a luminance value includes applying a different operation depending upon the row position of the pixel.

12. A method according to claim 1 wherein the subset of each of the pixels comprises each of the pixels that has an odd row number position and an odd column number position so that a Y, Cr and Cb component is generated for each of the pixels having an odd row number position and an odd column number position in the luminance and chrominance color space.

13. A method according to claim 1 wherein determining a luminance value for a specific pixel comprises using a median of the color values for pixels in the neighborhood of the specific pixel.

14. A method according to claim 1 wherein determining a chrominance value for a specific subset pixel comprises using a median of the color values for pixels in the neighborhood of the specific subset pixel.

15. A machine-readable medium having stored thereon data representing sequences of instructions which, when executed by a processor, cause the processor to perform the steps of:

determining a position of each of the pixels in an image, each pixel having at least one color value, as a row position and a column position;

for each of the pixels, determining a luminance value for a specific pixel using the color values for pixels in the neighborhood of the specific pixel;

for a subset of each of the pixels, determining a chrominance value for a specific subset pixel using the color values for pixels in the neighborhood of the specific subset pixel and applying a different operation depending upon the row position of the pixel; and

mapping the luminance and chrominance values into a luminance and chrominance color space.

16. A medium according to claim 15 wherein the neighborhood of a pixel includes the pixel.

17. A medium according to claim 15 wherein the neighborhood of a pixel includes pixels positioned no more than one row or column position away from the pixel.

18. A medium according to claim 15 wherein determining a luminance value includes applying a different operation depending upon the row position of the pixel.

19. A medium according to claim 15 wherein each of the pixels has either a red, green or blue color value and wherein determining a luminance value for a pixel location having a red color value includes determining a median of the green color values in the neighborhood of the red pixel, determining a median of the blue color values in the neighborhood of the red pixel, weighting the medians and the color value of the red pixel and adding the weighted medians and red color value to obtain the luminance.

20. A medium according to claim 15 wherein each of the pixels has either a red, green or blue color value and wherein determining a luminance value for a pixel location having a blue color value includes determining a median of the green color values in the neighborhood of the blue pixel, determining a median of the red color values in the neighborhood of the blue pixel, weighting the medians and the blue color value for the blue pixel and adding the weighted medians and blue color value to obtain the luminance.

21. A medium according to claim 15 wherein each of the pixels has either a red, green or blue color value and wherein determining a chrominance value for a pixel location having a green color value includes determining a median of the green color values in the neighborhood of the green pixel, determining a median of the blue color values in the neighborhood of the green pixel, determining a median of the red color values in the neighborhood of the green pixel, weighting the medians and adding the weighted medians to obtain the chrominance.

22. A medium according to claim 15 wherein, for each pixel having an odd-numbered row and column position, determining a luminance value includes applying a different operation depending upon the row position of the pixel.

23. A medium according to claim 15 wherein the subset of each of the pixels comprises each of the pixels that has an odd row number position and an odd column number position so that a Y, Cr and Cb component is generated for each of the pixels having an odd row number position and an odd column number position in the luminance and chrominance color space.

24. A method according to claim 15 wherein the subset of each of the pixel values excludes each of the pixels that does not have an odd row number position and an odd column number position so that only a Y component is generated for all other pixels in the luminance and chrominance color space.

25. A method according to claim 15 wherein determining a luminance value for a specific pixel comprises using a median of the color values for pixels in the neighborhood of the specific pixel.

26. A method according to claim 15 wherein determining a chrominance value for a specific subset pixel comprises using a median of the color values for pixels in the neighborhood of the specific subset pixel.