Method and system for edge detection

1. A method for operating a computer system for edge detection, comprising:

receiving an image comprising a plurality of pixels;

determining a phase congruency value for a pixel wherein the phase congruency value comprises a ratio of a first phase congruency component to a second phase congruency component;

determining if the phase congruency value satisfies a first criteria;

if the phase congruency value satisfies the first criteria, categorizing the pixel as an edge pixel;

if the phase congruency value does not satisfy the first criteria, determining if the first phase congruency component satisfies a second criteria different from the first criteria;

if the first phase congruency component satisfies the second criteria, categorizing the pixel as an edge pixel; and

if the first phase congruency component does not satisfy the second criteria, categorizing the pixel as a non-edge pixel.

2. The method of claim 1 , wherein the first phase congruency component comprises a local energy of the pixel.

3. The method of claim 1 , wherein the second phase congruency component comprises the sum of the amplitudes of the Fourier components of the image at the location of the pixel.

4. The method of claim 1 , wherein the first criteria comprises a phase congruency threshold value, and wherein determining if the phase congruency value satisfies the first criteria comprises determining if the phase congruency value exceeds the threshold value.

5. The method of claim 1 , wherein the second criteria comprises a phase congruency component threshold value, and wherein determining if the first phase congruency component satisfies the second criteria comprises determining if the phase congruency component exceeds the phase congruency component threshold value.

6. The method of claim 1 , wherein the image is a digital image from a transit system, and at least some of the edge pixels and corner pixels define outlines of human heads.

7. An image processing system for detecting edges comprising:

an interface configured to receive images; and

a processor electrically coupled with the interface;

wherein the processor is configured to:

receive an image comprising a plurality of pixels;

determine a phase congruency value for a pixel wherein the phase congruency value comprises a ratio of a first phase congruency component to a second phase congruency component;

determine if the phase congruency value satisfies a first criteria;

if the phase congruency value satisfies the first criteria, categorize the pixel as an edge pixel;

if the phase congruency value does not satisfy the first criteria, determine if the first phase congruency component satisfies a second criteria different from the first criteria;

if the first phase congruency component satisfies the second criteria, categorize the pixel as an edge pixel; and

if the first phase congruency component does not satisfy the second criteria, categorize the pixel as a non-edge pixel.

8. The image processing system of claim 7 , wherein the first phase congruency component comprises a local energy of the pixel.

9. The image processing system of claim 7 , wherein the second phase congruency component comprises the sum of the amplitudes of the Fourier components of the image at the location of the pixel.

10. The image processing system of claim 7 , wherein the first criteria comprises a phase congruency threshold value, and wherein determining if the phase congruency value satisfies the first criteria comprises determining if the phase congruency value exceeds the phase congruency threshold value.

11. The image processing system of claim 7 , wherein the second criteria comprises a phase congruency component threshold value, and wherein determining if the first phase congruency component satisfies the second criteria comprises determining if the phase congruency component exceeds the phase congruency component threshold value.

12. The image processing system of claim 7 , wherein the image is a digital image from a transit system, and at least some of the edge pixels and corner pixels define outlines of human heads.

13. A non-transitory computer-readable medium having instructions stored thereon for operating a computer system to detect edges, wherein the instructions, when executed by the computer system, direct the computer system to:

receive an image comprising a plurality of pixels;

determine a phase congruency value for a pixel wherein the phase congruency value comprises a ratio of a first phase congruency component to a second phase congruency component;

determine if the phase congruency value satisfies a first criteria;

if the phase congruency value satisfies the first criteria, categorize the pixel as an edge pixel;

if the phase congruency value does not satisfy the first criteria, determine if the first phase congruency component satisfies a second criteria different from the first criteria;

if the first phase congruency component satisfies the second criteria, categorize the pixel as an edge pixel; and

if the first phase congruency component does not satisfy the second criteria, categorize the pixel as a non-edge pixel.

14. The non-transitory computer-readable medium of claim 13 , wherein the first phase congruency component comprises a local energy of the pixel.

15. The non-transitory computer-readable medium of claim 13 , wherein the second phase congruency component comprises the sum of the amplitudes of the Fourier components of the image at the location of the pixel.

16. The non-transitory computer-readable medium of claim 13 , wherein the first criteria comprises a phase congruency threshold value, and wherein determining if the phase congruency value satisfies the first criteria comprises determining if the phase congruency value exceeds the phase congruency threshold value.

17. The non-transitory computer-readable medium of claim 13 , wherein the second criteria comprises a phase congruency component threshold value, and wherein determining if the first phase congruency component satisfies the second criteria comprises determining if the phase congruency component exceeds the phase congruency component threshold value.