Scaling algorithm and architecture for integer scaling in video

• US 6,348,929 B1
• Filed: 01/16/1998
• Issued: 02/19/2002
• Est. Priority Date: 01/16/1998
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Metz, Werner, Acharya, Tinku
• Primary Examiner(s): Luu, Matthew
• Assistant Examiner(s): Chung, Daniel J
• Application Number:
  US09/008,131
• Time in Patent Office: 1,495 Days
• Field of Search: 345/660, 345/67, 345/666, 345/667, 345/668, 345/669, 345/670, 345/671, 348/581, 348/273, 358/512, 358/525
• US Class Current: 345/660
• CPC Class Codes: G06T 3/4015 Image demosaicing, e.g. colour filter arrays [CFA] or Bayer patterns
• CPC Class Codes: H04N 19/59 involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution

Abstract

A method for scaling of an image that includes providing an N-tap filter to be applied upon an image region and applying the N-tap filter variously to the image region and obtaining therefrom at least one scaled image pixel, such that N is equal to the scaling factor plus one. For instance, a 4:1 scaling procedure is achieved using a five-tap filter. By carefully selecting the coefficient of the five-tap filter, 2:1 scaling with a three-tap filter may be achieved using the same hardware and adding control signals and selectors. The scaling methodology and apparatus work directly in the CFA domain and provide efficient single pass dual-moded or multi-moded scaling capability.

Claims

1. A method for scaling an image comprising:

providing an N-tap filter to be applied upon an image region, the image region including a plurality of sub-images each sub-image having pixels associated with a particular color plane; and

applying said N-tap filter separately to each said sub-image and obtaining therefrom at least one scaled image pixel for each said sub-image, storing said at least one scaled image pixel for each said sub-image in a scaled image array.

2. A method according to claim 1 wherein N has a value of 5 for a scaling factor of four to one.

3. A method according to claim 1 wherein applying said N-tap filter variously to said image region includes:

applying said N-tap filter in a vertical manner to said image region to obtain a first array of products; and

applying said N-tap filter in a horizontal manner to said first array of products to obtain therefrom a mask of products.

4. A method according to claim 3 further comprising:

summing together said mask products to obtain a mask result; and

normalizing said mask result by the total weighting of the mask, said total weighting the sum of the coefficients of the mask, said normalized result yielding the scaled image pixel.

5. A method according to claim 1 wherein said applying the N-tap filter is repeated for a plurality of image regions in addition to said image region, said repeated application yielding a plurality of scaled image pixels.

6. A method according to claim 5 wherein said plurality of scaled image pixels are stored into an array.

7. A method according to claim 5 wherein said plurality of scaled image pixels are sufficient to constitute the entire scaled image.

8. A method according to claim 1 wherein said color planes consist of a red color plane, a first green color plane, a second green color plane and a blue color plane.

9. A method according to claim 1 wherein the scaled image pixel is with the same color plane as the pixels of said sub-image region.

10. A method according to claim 2 wherein said taps of said filter are 1, 2, 2, 2 and 1.

11. A method according to claim 1 wherein N has a value of 3 for a scaling factor of two to one.

12. A method according to claim 11 wherein said taps of said filter are 1, 2 and 1.

13. A method according to claim 1 wherein said taps are selected to favor a central portion of said image region while maintaining the ability to represent edge features occurring elsewhere than said central portion.

27. A method according to claim 1 wherein a first of said sub-images has pixels associated with a first color plane and a second of said with a first color plane and a second of said sub-image has pixels also associated with said first color plane.

14. An apparatus for image processing comprising:

a dual-mode scaling unit, configured to provide a quarter scaled image in a first mode and a half scaled image in a second mode, said scaling unit including a five-tap filter, wherein said five-tap filter operates as a three-tap filter in said second mode.

15. An apparatus according to claim 14 wherein said five-tap filter operates in said first mode to provide taps of 1, 2, 2, 2, and 1.

16. An apparatus according to claim 14 wherein said five-tap filter operates in said second mode to provide taps of 0, 1, 2, 1, and 0.

17. An apparatus according to claim 14 wherein said scaling unit is composed of shift registers and buffers to provide said filter taps.

21. An apparatus according to claim 15, wherein said apparatus is operable to act upon a sub-image region having pixels associated with a particular color plane of a color filter array.

18. A system comprising:

an image capture device, said image capture device configured to capture an original image of a scene, said image capture device further configured to provide quarter or half scaled image data from said original image, wherein said system is operable to scale an image by operating upon a sub-image region having pixels associated with a particular color plane of a color filter array; and

a computer system coupled to said image capture device, said computer system configured to render said scaled image data.

19. A system according to claim 18 wherein said image capture device is configured to transport said scaled image data over a network.

20. A system according to claim 18 wherein said computer system is configured to perform videoconferencing, said image capture device providing scaled images for said videoconferencing.

22. An apparatus comprising:

an image having regions;

an N-tap filter for scaling said image according to a first scaling factor, wherein;

said N-tap filter is operable to act as a filter with fewer than N taps for scaling said image according to a second scaling factor, and

said N-tap filter is operable to be applied to an image region and to obtain therefrom at least one scaled image pixel according to one of either said first or said second scaling factor; and

a buffer operable to store said scale pixels.

23. An apparatus according to claim 22, wherein said N-tap filter is a five-tap filter and wherein said five-tap filter is operable to act as a three-tap filter.

24. An apparatus according to claim 22, wherein said N-tap filter is converted to operation as a filter with fewer than N taps by forcing one or more of the filter tap coefficients to zero.

25. An apparatus according to claim 24, wherein said one or more filter tap coefficients are forced to zero by suppressing the output of said buffer.

26. An apparatus according to claim 22, wherein said image region is a sub-image region having pixels associated with a particular color plane of a color filter array.