Methods and apparatus for re-scaling image by variable re-scaling factor using B-spline interpolator

• US 20060221245A1
• Filed: 03/30/2005
• Published: 10/05/2006
• Est. Priority Date: 03/30/2005
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Kurupati, Sreenath, Hormis, Raju, Liang, Kuo-Ching
• Granted Patent: US 7,446,820 B2
• Time in Patent Office: Days
• US Class Current: 348/581
• CPC Class Codes: G06T 3/4007 based on interpolation, e.g. bilinear interpolation image demosaicing G06T3/4015; edge-driven or edge-based scaling G06T3/403

Abstract

A method includes receiving a sequence of input samples that represents a row of pixels in an image. The method further includes selecting a re-scaling factor for at least a portion of the row of pixels. The method further includes determining a phase offset based on the selected re-scaling factor, and applying a direct B-spline transform to a group of the samples to generate transform coefficients. The method further includes providing the transform coefficients as an input to a filter bank, and applying the phase offset at an output of the filter bank to generate a sequence of output samples.

Claims

1. A method comprising:

receiving a sequence of input samples that represents a row of pixels in an image;

selecting a re-scaling factor for at least a portion of said row of pixels;

determining a phase offset based on said selected re-scaling factor;

applying a direct B-spline transform to a group of said samples to generate transform coefficients;

providing the transform coefficients as an input to a filter bank; and

applying said phase offset at an output of said filter bank to generate a sequence of output samples.

2. The method of claim 1, wherein said re-scaling factor is changed along said row of pixels.

3. The method of claim 1, wherein the direct B-spline transform is a cubic B-spline transform.

4. The method of claim 1, further comprising:

providing a bank of low pass filters;

selecting a filter from said bank of low pass filters based on the selected re-scaling factor; and

low-pass filtering said sequence of input samples with the selected filter from said bank of low pass filters.

5. The method of claim 1, further comprising:

low-pass filtering said sequence of output samples; and

down-sampling said low-pass-filtered sequence of output samples.

6. The method of claim 1, further comprising:

low-pass filtering said sequence of input samples before applying the direct B-spline transform thereto; and

down-sampling said sequence of output samples.

7. A system comprising:

a transform block to receive a sequence of input samples and to apply a direct B-spline transform to a group of said samples to generate transform coefficients, said sequence of input samples representing a row of pixels in an image;

a filter bank coupled to the transform block to receive the transform coefficients;

a re-scaling factor block to select a re-scaling factor for at least a portion of said row of pixels;

a phase-offset determination block coupled to the re-scaling factor block to determine a phase offset based on the re-scaling factor selected by the re-scaling factor block; and

an array of adders and multipliers coupled to an output of said filter bank and also coupled to said phase-offset determination block, said array of adders and multipliers to generate a sequence of output samples by applying said phase offset to signals output from said filter bank.

8. The system of claim 7, wherein the re-scaling factor block is operative to change the re-scaling factor along said row of pixels.

9. The system of claim 7, wherein the direct B-spline transform is a cubic B-spline transform.

10. The system of claim 7, further comprising:

a bank of low pass filters coupled upstream from said transform block, said bank of low pass filters also coupled to said re-scaling factor block, said re-scaling factor block operative to select a filter from said bank of low pass filters, said selected low pass filter operative to low-pass filter said sequence of input samples.

11. The system of claim 7, further comprising:

a low pass filter coupled downstream from the array of adders and multipliers to low-pass filter said sequence of output samples; and

a down-sample block coupled downstream from the low pass filter to down-sample said low-pass-filtered sequence of output samples.

12. The system of claim 7, further comprising:

a low pass filter coupled upstream from said transform block to low-pass filter said sequence of input samples; and

a down-sample block coupled downstream from said array of adders and multipliers to down-sample said sequence of output samples.

13. The system of claim 7, wherein the transform block, the filter bank, the re-scaling factor block, the phase-offset determination block and the array of adders and multipliers are included in a video-processing integrated circuit (IC), the system further comprising a graphics memory unit in communication with the video-processing IC.

14. A method comprising:

selecting a re-scaling factor for at least a portion of an image;

determining a phase offset based on said selected re-scaling factor;

applying a direct B-spline transform to a group of samples that represent said portion of said image, said direct B-spline transform producing transform coefficients;

providing the transform coefficients as an input to a filter bank; and

applying said phase offset at an output of said filter bank to generate a sequence of output samples.

15. The method of claim 14, further comprising:

varying said re-scaling factor from one portion of said image to another portion of said image.

16. The method of claim 14, wherein the direct B-spline transform is a cubic B-spline transform.

17. The method of claim 14, further comprising:

providing a bank of low pass filters;

selecting a filter from said bank of low pass filters based on the selected re-scaling factor; and

low-pass filtering a sequence of input samples with the selected filter from said bank of low pass filters, said sequence of input samples representing said image.

18. The method of claim 14, further comprising:

low-pass filtering said sequence of output samples; and

down-sampling said low-pass-filtered sequence of output samples.

19. The method of claim 14, further comprising:

down-sampling said sequence of output samples.