System and method for a vector difference mean filter for noise suppression

• US 20060103892A1
• Filed: 11/18/2004
• Published: 05/18/2006
• Est. Priority Date: 11/18/2004
• Status: Abandoned Application

• Current Assignee: Sozotek, Inc.
• Original Assignee: Sozotek, Inc.
• Inventors: Schulze, Mark A., John, George
• Application Number:
  US10/992,409
• Publication Number:
  US 20060103892A1
• Time in Patent Office: Days
• US Class Current: 358/463
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/75 Unsharp masking
• CPC Class Codes: G06V 10/30 Noise filtering
• CPC Class Codes: H04N 1/58 Edge or detail enhancement; Noise or error suppression, e.g. colour misregistration correction H04N1/62 takes precedence

Abstract

Reduction of noise in digitized multi-spectral images is provided by filtering based on vector values rather than independent scalar values. Vector values refer to a pixel with two or more values. For this method, a metric is defined for pixel vector magnitude. A sliding processing kernel is also defined, with a specified shape, a specified number of pixels to be included in the kernel, and a specified value contrast threshold to avoid distorting edges and fine details. The metric and kernel are used to select pixels for computing filtering of the center pixel in a kernel. A statistical measurement is computed, for example by mean averaging the specified pixels, and the resulting value is made the value of the center pixel of the kernel. The filtering process is applied throughout the image by making each pixel the center of a processing kernel.

Claims

1. An automated method for filtering digitized multi-spectral images to suppress noise, the images comprising a plurality of pixels, the pixels each having vector values comprising a plurality of spectral components, the method comprising the computer-implemented steps of

creating filtering software, such that the filtering software filters an image according to the vector values of at least a portion of the plurality of pixels within the image;

receiving a digital image;

filtering the digital image using the filtering software; and

returning a filtered image.

2. The method of claim 1 wherein the vector values of at least a portion of the plurality of pixels further comprise

a red scalar color component value for each of the plurality of pixels;

a green scalar color component value for each of the plurality of pixels; and

a blue scalar color component value for each of the plurality of pixels.

3. The method of claim 1 wherein the vector values of at least a portion of the plurality of pixels further comprise

a cyan scalar color component value for each of the plurality of pixels;

a magenta scalar color component value for each of the plurality of pixels;

a yellow scalar color component value for each of the plurality of pixels; and

a black scalar color component value for each of the plurality of pixels.

4. The method of claim 1 wherein creating filtering software, such that the filtering software filters an image according to the vector values of the plurality of pixels within the image further comprises

defining a metric, such that the metric uses the vector values of a first pixel and a second pixel to determine a metric value for the pixel;

and

filtering each of the portion of the plurality of pixels within the image by designating a center pixel;

defining a sliding processing kernel relative to the center pixel, the kernel comprising kernel pixels which include the center pixel and a plurality of pixels in proximity to the center pixel;

for each pixel associated with the sliding processing kernel

using the metric to compute the metric value for the pixel from the center pixel vector value and the pixel vector value,

comparing the metric value for the pixel to a threshold value for the kernel pixels in order to determine whether to include the pixel value in a filter calculation for the center pixel,

performing the filter calculation for the center pixel using the metric values for the those kernel pixels which were determined to be included in the filter calculation, and

replacing the vector value of the center pixel with a calculated vector value from the filter calculation for the center pixel.

5. The method of claim 4 wherein defining a metric further comprises

determining the simple vector distance between the vector values of the center pixel and a second pixel.

6. The method of claim 4 wherein defining a sliding processing kernel relative to the center pixel further comprises

selecting a kernel shape relative to the center pixel;

setting a kernel size; and

setting a value contrast threshold for the kernel.

7. The method of claim 6 wherein setting a kernel size further comprises

setting a kernel size dynamically based on the intensity of an image and on a magnitude threshold value.

8. The method of claim 7 wherein setting a kernel size dynamically based on the intensity of an image and on a magnitude threshold value further comprises

using the magnitude threshold value to detect that a portion of an image is of low intensity;

and

setting a large kernel size for the low intensity portion of an image.

9. The method of claim 8 wherein using a magnitude threshold value to detect that an image is of low intensity further comprises

setting the magnitude threshold value as the standard deviation of the magnitude of the overall image subtracted from the mean overall magnitude of the image.

10. The method of claim 7 wherein setting a value contrast threshold for the kernel further comprises

using a statistical method to set a value contrast threshold.

11. The method of claim 7 wherein setting a value contrast threshold further comprises

setting a value contrast threshold dynamically through a statistical method comprising

taking the mean average of the vector values of the pixels in the kernel;

finding the standard deviation of the vector values of the pixels in the kernel; and

setting the value contrast threshold to the mean average plus the standard deviation.

12. An automated method for filtering digitized multi-spectral images to suppress noise, the images comprising a plurality of pixels, the pixels each having vector values comprising a plurality of spectral components, the method comprising the computer-implemented steps of

creating filtering software, such that the filtering software filters an image according to the vector values of the plurality of pixels within the image by

defining a metric, such that the metric uses the vector values of a first pixel and a second pixel to determine a metric value for the pixel, and

filtering each of the portion of the plurality of pixels within the image by designating a center pixel,

defining a sliding processing kernel relative to the center pixel, the kernel comprising a plurality of kernel pixels by

selecting a kernel shape relative to the center pixel, such that the kernel comprises the center pixel and a plurality of pixels in proximity to the center pixel,

setting a kernel size, and

setting a value contrast threshold for the kernel, and

for each kernel pixel,

using the metric to compute the metric value for the pixel from the center pixel vector value and the pixel vector value,

comparing the metric value for the pixel to a threshold value for the kernel pixels in order to determine whether to include the pixel value in a filter calculation for the center pixel,

performing the filter calculation for the center pixel using the metric values for those kernel pixels which were determined to be included in the filter calculation, and

replacing the vector value of the center pixel with a calculated vector value from the filter calculation for the center pixel;

receiving a digital image;

filtering the digital image using the filtering software; and

returning a filtered image.

13. The method of claim 12 wherein the vector values of at least a portion of the plurality of pixels further comprise

a red scalar color component value for each of the plurality of pixels;

a green scalar color component value for each of the plurality of pixels; and

a blue scalar color component value for each of the plurality of pixels.

14. The method of claim 12 wherein defining a metric further comprises

determining the simple vector distance between the vector values of the center pixel and a second pixel.

15. The method of claim 12 wherein setting a kernel size further comprises setting a kernel size dynamically based on the intensity of an image and on a magnitude threshold value by

using the magnitude threshold value to detect that a portion of an image is of low intensity;

and

setting a large kernel size for the low intensity portion of an image.

16. The method of claim 15 wherein using a magnitude threshold value to detect that an image is of low intensity further comprises

setting the magnitude threshold value as the standard deviation of the magnitude of the overall image subtracted from the mean overall magnitude of the image.

17. The method of claim 12 wherein setting a value contrast threshold for the kernel further comprises

using a statistical method to set a value contrast threshold.

18. The method of claim 17 wherein setting a value contrast threshold further comprises

setting a value contrast threshold dynamically through a statistical method, the statistical method comprising

taking the mean average of the vector values of the pixels in the kernel;

finding the standard deviation of the vector values of the pixels in the kernel; and

setting the value contrast threshold to the mean average plus the standard deviation.

19. A method of sharpening digitized multi-spectral images, the method comprising performing a spatial average of a digitized multi-spectral image A to obtain a blurred image B1 with noise and signal suppressed;

subtracting the resulting blurred image B1 from the original image A to produce a high frequency band C1 that contains noise and signal;

using filtering software based on vector values of pixels in the original image A to produce a filtered image B2 with noise suppressed;

subtracting the filtered image B2 from the original image A to produce a noise band C2 that contains noise with very little signal;

subtracting the noise band C2 from the high frequency band C1 to produce a signal band D that contains the signal; and

adding the signal band D to the filtered image B2 to further enhance detail in the noise filtered band.

20. A system for filtering digitized multi-spectral images to suppress noise, the system comprising

a computing environment;

means for receiving a digitized multi-spectral image from a source environment;

filtering software based on vector values of a plurality of pixels within the image, the software providing a filtered image by

defining a metric, such that the metric uses the vector values of a first pixel and a second pixel to determine a metric value for the pixel, and

filtering each of the portion of the plurality of pixels within the image by designating a center pixel,

defining a sliding processing kernel relative to the center pixel, the kernel comprising kernel pixels which include the center pixel and a plurality of pixels in proximity to the center pixel,

for each pixel associated with the sliding processing kernel

using the metric to compute the metric value for the pixel from the center pixel vector value and the pixel vector value, and

comparing the metric value for the pixel to a threshold value for the kernel pixels in order to determine whether to include the pixel value in a filter calculation for the center pixel,

performing the filter calculation for the center pixel using the metric values for the those kernel pixels which were determined to be included in the filter calculation, and

replacing the vector value of the center pixel with a calculated vector value from the filter calculation for the center pixel; and

a means for transmitting the filtered image to a target environment.

22. A system for providing filtered digitized multi-spectral images, the system comprising

a means of capturing digitized multi-spectral images;

and

a microprocessor containing filtering software based on vector values of a plurality of pixels within the image, the software providing a filtered image by

defining a metric, such that the metric uses the vector values of a first pixel and a second pixel to determine a metric value for the pixel; and

filtering each of the portion of the plurality of pixels within the image by designating a center pixel,

defining a sliding processing kernel relative to the center pixel, the kernel comprising kernel pixels which include the center pixel and a plurality of pixels in proximity to the center pixel,

for each pixel associated with the sliding processing kernel

using the metric to compute the metric value for the pixel from the center pixel vector value and the pixel vector value, and

comparing the metric value for the pixel to a threshold value for the kernel pixels in order to determine whether to include the pixel value in a filter calculation for the center pixel,

performing the filter calculation for the center pixel using the metric values for the those kernel pixels which were determined to be included in the filter calculation, and

replacing the vector value of the center pixel with a calculated vector value from the filter calculation for the center pixel.