METHOD AND APPARATUS FOR SHELF EDGE DETECTION

• US 20190073559A1
• Filed: 09/07/2017
• Published: 03/07/2019
• Est. Priority Date: 09/07/2017
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Inventors: Rzeszutek, Richard Jeffrey, Gorodetsky, Vlad
• Granted Patent: US 10,489,677 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 16/583 using metadata automatically derived from the content
• CPC Class Codes: G06Q 10/087 Inventory or stock management, e.g. order filling, procurement or balancing against orders
• CPC Class Codes: G06V 10/28 Quantising the image, e.g. histogram thresholding for discrimination between background and foreground patterns
• 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
• CPC Class Codes: G06V 10/473 using gradient analysis
• CPC Class Codes: G06V 10/48 by mapping characteristic values of the pattern into a parameter space, e.g. Hough transformation
• CPC Class Codes: G06V 10/759 Region-based matching
• CPC Class Codes: G06V 20/00 Scenes; Scene-specific elements control of digital cameras H04N23/60
• CPC Class Codes: G06V 20/20 in augmented reality scenes

Abstract

A method of label detection includes: obtaining, by an imaging controller, an image depicting a shelf; increasing an intensity of a foreground subset of image pixels exceeding an upper intensity threshold, and decreasing an intensity of a background subset of pixels below a lower intensity threshold; responsive to the increasing and the decreasing, (i) determining gradients for each of the pixels and (ii) selecting a candidate set of the pixels based on the gradients; overlaying a plurality of shelf candidate lines on the image derived from the candidate set of pixels; identifying a pair of the shelf candidate lines satisfying a predetermined sequence of intensity transitions; and generating and storing a shelf edge bounding box corresponding to the pair of shelf candidate lines.

Claims

1. A method of detecting a shelf edge by an imaging controller, comprising:

obtaining, by the imaging controller, an image depicting a shelf;

increasing an intensity of a foreground subset of image pixels in the image, wherein each pixel in the foreground subset of pixels has an initial intensity that exceeds an upper intensity threshold, and decreasing an intensity of a background subset of pixels in the image, wherein each pixel in the background subset of pixels has an initial intensity that is below a lower intensity threshold;

responsive to the increasing and the decreasing, (i) determining gradients for each of the pixels and (ii) selecting a candidate set of the pixels based on the gradients;

overlaying a plurality of shelf candidate lines on the image derived from the candidate set of pixels;

identifying a pair of the shelf candidate lines satisfying a predetermined sequence of intensity transitions; and

generating a shelf edge bounding box corresponding to the pair of shelf candidate lines.

2. The method of claim 1, further comprising downsampling the image prior to the increasing and the decreasing.

3. The method of claim 1, further comprising:

adjusting an intensity of an intermediate subset of pixels having intensities between the upper intensity threshold and the lower intensity threshold.

4. The method of claim 3, further comprising:

prior to the increasing, the decreasing and the adjusting, determining intensity adjustment parameters by comparing pixel populations of the foreground subset and the background subset to target foreground and background populations.

5. The method of claim 1, wherein selecting the candidate set of pixels comprises selecting pixels presenting locally maximal gradients in an orientation perpendicular to an expected orientation of the shelf edge.

6. The method of claim 1, wherein overlaying the plurality of shelf candidate lines comprises:

assigning each pixel in the candidate set to one of a plurality of bins, each bin corresponding to a line;

selecting candidate subsets of the pixels assigned to respective bins having pixel populations exceeding a population threshold; and

generating a shelf candidate line from each candidate subset of pixels.

7. The method of claim 1, wherein the identifying further comprises:

traversing the image in a predefined direction; and

evaluating successive pairs of the shelf candidate lines against the intensity sequence.

8. The method of claim 1, wherein the identifying further comprises determining whether the pair of shelf candidate lines satisfying the predetermined sequence satisfy a spacing criterion.

9. The method of claim 8, wherein the spacing criterion defines a minimum distance between the pair of shelf candidate lines and a maximum distance between the pair of shelf candidate lines.

10. The method of claim 1, further comprising storing the shelf edge bounding box in a memory.

11. A computing device for detecting shelf edges, comprising:

a memory; and

an imaging controller, coupled to the memory, the imaging controller including;

a preprocessor configured to obtain an image depicting a shelf, and to increase an intensity of a foreground subset of pixels in the image, wherein each pixel in the foreground subset of pixels has an initial intensity that exceeds an upper intensity threshold, and decrease an intensity of a background subset of pixels in the image, wherein each pixel in the background subset of pixels has an initial intensity that is below a lower intensity threshold;

a selector configured, responsive to the increasing and the decreasing, to (i) determine gradients for each of the pixels and (ii) select a candidate set of the pixels based on the gradients;

a line generator configured to overlay a plurality of shelf candidate lines on the image derived from the candidate set of pixels; and

a region generator configured to identify a pair of the shelf candidate lines satisfying a predetermined sequence of intensity transitions; and

the imaging controller configured to generate a shelf edge bounding box corresponding to the pair of shelf candidate lines in the memory.

12. The computing device of claim 11, wherein the preprocessor is further configured to downsample the image prior to the increasing and the decreasing.

13. The computing device of claim 11, wherein the preprocessor is further configured to:

adjust an intensity of an intermediate subset of pixels having intensities between the upper intensity threshold and the lower intensity threshold.

14. The computing device of claim 13, wherein the processor is further configured to:

prior to the increasing, the decreasing and the adjusting, determine intensity adjustment parameters by comparing pixel populations of the foreground subset and the background subset to target foreground and background populations.

15. The computing device of claim 11, wherein the selector is further configured to select the candidate set of pixels by selecting pixels presenting locally maximal gradients in an orientation perpendicular to an expected orientation of the shelf edge.

16. The computing device of claim 11, wherein the line generator is configured to overlay the plurality of shelf candidate lines by:

assigning each pixel in the candidate set to one of a plurality of bins each corresponding to a line;

selecting candidate subsets of the pixels assigned to respective bins having pixel populations exceeding a threshold; and

generating a shelf candidate line from each candidate subset of pixels.

17. The computing device of claim 11, wherein the region generator is configured to identify the pair of shelf candidate lines by:

traversing the image in a predefined direction; and

evaluating successive pairs of the shelf candidate lines against the intensity sequence.

18. The computing device of claim 11, wherein the region generator is further configured to identify the pair of shelf candidate lines by:

determining whether the pair of shelf candidate lines satisfying the predetermined sequence satisfy a spacing criterion.

19. The computing device of claim 18, wherein the spacing criterion defines a minimum distance between the pair of shelf candidate lines and a maximum distance between the pair of shelf candidate lines.

20. The computing device of claim 11, wherein the imaging controller is further configured to store the shelf edge bounding box in the memory.