COMPUTER-READABLE STORAGE MEDIUM, IMAGE RECOGNITION APPARATUS, IMAGE RECOGNITION SYSTEM, AND IMAGE RECOGNITION METHOD

• US 20120219227A1
• Filed: 07/29/2011
• Published: 08/30/2012
• Est. Priority Date: 02/24/2011
• Status: Active Grant

• Current Assignee: Nintendo Company Limited
• Original Assignee: Nintendo Company Limited
• Inventors: OSAKO, Satoru
• Granted Patent: US 8,705,868 B2
• Time in Patent Office: Days
• US Class Current: 382/199
• CPC Class Codes: G06T 2207/20012 Locally adaptive
• CPC Class Codes: G06T 2207/20164 Salient point detection; Corner detection
• CPC Class Codes: G06T 7/12 Edge-based segmentation
• CPC Class Codes: G06T 7/13 Edge detection
• CPC Class Codes: G06T 7/136 involving thresholding
• CPC Class Codes: G06V 10/44 Local feature extraction by analysis of parts of the pattern, e.g. by detecting edges, contours, loops, corners, strokes or intersections; Connectivity analysis, e.g. of connected components

Abstract

First, a difference between a pixel value of a first pixel in an image and a pixel value of a second pixel is calculated, the second pixel placed a predetermined number of pixels away from the first pixel. Then, when the difference is equal to or greater than a predetermined value, an edge determination threshold is calculated on the basis of: the pixel value of the first pixel or a pixel value of a pixel near the first pixel; and the pixel value of the second pixel or a pixel value of a pixel near the second pixel. Then, an edge pixel corresponding to an edge present between the first pixel and the second pixel is detected by comparing the edge determination threshold with a pixel value of each pixel placed between the first pixel and the second pixel.

Claims

1. A computer-readable storage medium having stored thereon an image recognition program causing a computer of an information processing apparatus to function as:

image acquisition means for acquiring an image;

difference calculation means for calculating a difference between a pixel value of a first pixel in the image and a pixel value of a second pixel, the second pixel placed a predetermined number of pixels away from the first pixel;

threshold calculation means for calculating an edge determination threshold on the basis of;

the pixel value of the first pixel or a pixel value of a pixel near the first pixel when the difference is equal to or greater than a predetermined value; and

the pixel value of the second pixel corresponding to the first pixel or a pixel value of a pixel near the second pixel; and

edge pixel detection means for detecting an edge pixel corresponding to an edge present between the first pixel and the second pixel, by comparing the edge determination threshold with a pixel value of each pixel placed between the first pixel and the second pixel.

2. The computer-readable storage medium according to claim 1, wherein

the threshold calculation means includes:

first detection means for detecting a local maximum value from among the pixel values of one of the first pixel and the second pixel having a larger pixel value and pixel values of pixels around the pixel having the larger pixel value; and

first calculation means for calculating the edge determination threshold on the basis of the local maximum value detected by the first detection means.

3. The computer-readable storage medium according to claim 2, wherein

the first detection means detects the local maximum value by sequentially determining a large/small relationship between pixel values of two adjacent pixels, starting from the one of the first pixel and the second pixel having the larger pixel value in a direction opposite to the pixel having the smaller pixel value.

4. The computer-readable storage medium according to claim 1, wherein

the threshold calculation means includes:

second determination means for determining whether or not a pixel value of a specific near pixel satisfies a predetermined condition, the specific near pixel placed a predetermined number of pixels away from one of the first pixel and the second pixel having a smaller pixel value in a direction opposite to the pixel having the larger pixel value; and

second calculation means for, when the second determination means has determined that the predetermined condition is satisfied, calculating the edge determination threshold on the basis of the pixel value of the specific near pixel.

5. The computer-readable storage medium according to claim 4, wherein

when the pixel value of the one of the first pixel and the second pixel having the smaller pixel value is smaller than the pixel value of the specific near pixel, and a difference between the pixel value of the specific near pixel and the pixel value of the one of the first pixel and the second pixel having the larger pixel value, or the pixel near the pixel having the larger pixel value, is equal to or greater than the predetermined value, the second determination means determines that the predetermined condition is satisfied.

6. The computer-readable storage medium according to claim 1, wherein

the threshold calculation means calculates, as the edge determination threshold, an average value of the pixel value of the first pixel or the pixel near the first pixel, and the pixel value of the second pixel or the pixel near the second pixel.

7. The computer-readable storage medium according to claim 1, the image recognition program further causing the computer to function as:

other-edge-pixel detection means for, on the basis of the edge determination threshold, detecting an edge pixel in a portion different from a part of the edge corresponding to the edge pixel detected by the edge pixel detection means.

8. The computer-readable storage medium according to claim 7, wherein

the other-edge-pixel detection means detects, from among a plurality of pixels adjacent to an already detected edge pixel, a new edge pixel continuous with the edge pixel on the basis of the edge determination threshold.

9. The computer-readable storage medium according to claim 7, the image recognition program further causing the computer to function as:

coincidence determination means for determining whether or not the new edge pixel detected by the other-edge-pixel detection means coincides with any of already detected edge pixels, wherein

when the coincidence determination means has determined a predetermined number of consecutive times that the new edge pixel sequentially detected by the other-edge-pixel detection means coincides with any of the already detected edge pixels, the other-edge-pixel detection means suspends a process of sequentially detecting a new edge pixel.

10. The computer-readable storage medium according to claim 7, wherein

on the basis of the edge determination threshold, the other-edge-pixel detection means repeatedly detects edge pixels continuous with the edge corresponding to the edge pixel detected by the edge pixel detection means,

the image recognition program further causing the computer to function as:

area detection means for detecting an area specified by the edge pixels detected by the other-edge-pixel detection means.

11. The computer-readable storage medium according to claim 1, wherein

when a pixel value of a pixel around one of the first pixel and the second pixel having a larger pixel value is larger than the pixel value of the pixel having the larger pixel value, the threshold calculation means calculates the edge determination threshold on the basis of the pixel value of the pixel around the pixel having the larger pixel value.

12. The computer-readable storage medium according to claim 1, wherein

the image acquisition means repeatedly acquires images, and

the difference calculation means calculates a difference between the pixel value of the first pixel in the images repeatedly acquired by the image acquisition means and the pixel value of the second pixel placed a predetermined number of pixels away from the first pixel.

13. The computer-readable storage medium according to claim 1, wherein

the image acquisition means acquires the image from a capturing device connected to the information processing apparatus.

14. An image recognition apparatus comprising:

image acquisition means for acquiring an image;

difference calculation means for calculating a difference between a pixel value of a first pixel in the image and a pixel value of a second pixel, the second pixel placed a predetermined number of pixels away from the first pixel;

threshold calculation means for calculating an edge determination threshold on the basis of;

the pixel value of the first pixel or a pixel value of a pixel near the first pixel when the difference is equal to or greater than a predetermined value; and

the pixel value of the second pixel corresponding to the first pixel or a pixel value of a pixel near the second pixel; and

edge pixel detection means for detecting an edge pixel corresponding to an edge present between the first pixel and the second pixel, by comparing the edge determination threshold with a pixel value of each pixel placed between the first pixel and the second pixel.

15. An image recognition method comprising:

an image acquisition step of acquiring an image;

a difference calculation step of calculating a difference between a pixel value of a first pixel in the image and a pixel value of a second pixel, the second pixel placed a predetermined number of pixels away from the first pixel;

a threshold calculation step of calculating an edge determination threshold on the basis of;

the pixel value of the first pixel or a pixel value of a pixel near the first pixel when the difference is equal to or greater than a predetermined value; and

the pixel value of the second pixel corresponding to the first pixel or a pixel value of a pixel near the second pixel; and

an edge pixel detection step of detecting an edge pixel corresponding to an edge present between the first pixel and the second pixel, by comparing the edge determination threshold with a pixel value of each pixel placed between the first pixel and the second pixel.

16. An image recognition system comprising:

image acquisition means for acquiring an image;

difference calculation means for calculating a difference between a pixel value of a first pixel in the image and a pixel value of a second pixel, the second pixel placed a predetermined number of pixels away from the first pixel;

threshold calculation means for calculating an edge determination threshold on the basis of;

the pixel value of the first pixel or a pixel value of a pixel near the first pixel when the difference is equal to or greater than a predetermined value; and

the pixel value of the second pixel corresponding to the first pixel or a pixel value of a pixel near the second pixel; and

edge pixel detection means for detecting an edge pixel corresponding to an edge present between the first pixel and the second pixel, by comparing the edge determination threshold with a pixel value of each pixel placed between the first pixel and the second pixel.

17. An image recognition system including an image recognition apparatus and a marker, the image recognition apparatus comprising:

a capturing section for capturing the marker;

image acquisition means for acquiring an image from the capturing section;

difference calculation means for calculating a difference between a pixel value of a first pixel in the image and a pixel value of a second pixel, the second pixel placed a predetermined number of pixels away from the first pixel;

threshold calculation means for calculating an edge determination threshold on the basis of;

the pixel value of the first pixel or a pixel value of a pixel near the first pixel when the difference is equal to or greater than a predetermined value; and

the pixel value of the second pixel corresponding to the first pixel or a pixel value of a pixel near the second pixel; and

edge pixel detection means for detecting an edge pixel corresponding to an edge present between the first pixel and the second pixel, by comparing the edge determination threshold with a pixel value of each pixel placed between the first pixel and the second pixel.