Edge detection technique having improved feature visibility

• US 8,300,949 B2
• Filed: 05/18/2010
• Issued: 10/30/2012
• Est. Priority Date: 05/18/2010
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Xu, Xinyu
• Primary Examiner(s): Wu, Jingge
• Assistant Examiner(s): SHAH, UTPAL D
• Application Number:
  US12/782,461
• Publication Number:
  US 20110286671A1
• Time in Patent Office: 896 Days
• Field of Search: 382/199, 382/266
• US Class Current: 382/199
• CPC Class Codes: G06T 7/13 Edge detection

Abstract

A method for determining edge features of an image comprising filtering at least a portion of the image to attenuate high frequency signals of the image to an extent greater than low frequency signals of the image. Performing a one-dimensional search in a two different horizontal directions relative to a particular pixel of the image to determine horizontal direction local maximums. Calculating a horizontal gradient based upon the horizontal direction local maximums. Performing a one-dimensional search in a two vertical horizontal directions relative to a particular pixel of the image to determine vertical direction local maximums. Calculating a vertical gradient based upon the vertical direction local maximums. Calculating a gradient for the particular pixel based upon the horizontal gradient and the vertical gradient.

Claims

1. A method for determining edge features of an image comprising:

(a) filtering at least a portion of said image to attenuate high frequency signals of said image to an extent greater than low frequency signals of said image;

(b) performing a one-dimensional search in a first horizontal direction relative to a particular pixel of said image to determine a first horizontal direction local maximum;

(c) performing a one-dimensional search in a second horizontal direction relative to said particular pixel of said image to determine a second horizontal direction local maximum;

(d) calculating a horizontal gradient based upon said first horizontal direction local maximum and said second horizontal direction local maximum;

(e) performing a one-dimensional search in a first vertical direction relative to a particular pixel of said image to determine a first vertical direction local maximum;

(f) performing a one-dimensional search in a second vertical direction relative to said particular pixel of said image to determine a second vertical direction local maximum;

(g) calculating a vertical gradient based upon said first vertical direction local maximum and said second vertical direction local maximum;

(h) calculating a gradient for said particular pixel based upon said horizontal gradient and said vertical gradient.

2. The method of claim 1 wherein said first and second horizontal directions are based upon more than 3 pixels.

3. The method of claim 1 wherein said first and second vertical directions are based upon more than 3 pixels.

4. The method of claim 1 wherein said gradient is thresholded.

5. The method of claim 1 wherein said horizontal searches and vertical searches are independent of one another.

6. The method of claim 1 wherein said calculating said horizontal gradient is based upon the summation of said first and second horizontal gradients.

7. The method of claim 1 wherein said calculating said vertical gradient is based upon the summation of said first and second vertical gradients.

8. The method of claim 1 wherein said gradient is based upon the larger of said vertical gradient and said horizontal gradients.

9. The method of claim 1 wherein said calculations are based upon the gray scale of said image.

10. The method of claim 1 further comprising down-sampling said image.