Image block selection for efficient time-limited decoding

Patent metadata

Field	Value
Publication number	US-9922220-B2
Application number	US-201615176498-A
Country	US
Kind code	B2
Filing date	Jun 8, 2016
Priority date	Jun 11, 2015
Publication date	Mar 20, 2018
Grant date	Mar 20, 2018

Abstract

Object recognition by point-of-sale camera systems is aided by first removing perspective distortion. Yet pose of the object—relative to the system—depends on actions of the operator, and is usually unknown. Multiple trial counter-distortions to remove perspective distortion can be attempted, but the number of such trials is limited by the frame rate of the camera system—which limits the available processing interval. One embodiment of the present technology examines historical image data to determine counter-distortions that statistically yield best object recognition results. Similarly, the system can analyze historical data to learn what sub-parts of captured imagery most likely enable object recognition. A set-cover strategy is desirably used. In some arrangements, the system identifies different counter-distortions, and image sub-parts, that work best with different clerk- and customer-operators of the system, and processes captured imagery accordingly. A great variety of other features and arrangements are also detailed.

First claim

The invention claimed is:

1. A method of enhancing operation of a visual recognition system that is allotted a limited time interval to produce an identification result, which system includes a camera that provides image frames for extraction of digital watermark data therefrom, the method comprising the acts:
(a) for one sub-part of one image frame, applying at least M different values of tilt-angle correction in attempting to extract digital watermark data from M resultant tilt angle-corrected counterparts of said one sub-part of said one image frame, where M>1;
(b) performing act (a) at least N times, each with a differently-located sub-part of said one image frame, where N>1, wherein extraction of digital watermark data from said one image frame is attempted for at least M*N combinations of tilt angle correction values and sub-part locations;
(c) performing act (b) plural times, each with a different image frame drawn from a set P of image frames;
(d) determining which single combination of tilt angle correction value and sub-part location resulted in successful extraction of digital watermark data from a greatest number of said image frames in said set P; adding this combination of tilt angle correction value and sub-part location to a listing of decoding parameters; and removing, from the set P, those image frames from which digital watermark data was successfully extracted using said combination of tilt angle correction value and sub-part location; and
(e) repeating act (d) one or more times with successively smaller sets P;
wherein the method yields a listing of decoding parameters that is ranked by likelihood of successfully extracting unique digital watermark data from an image frame, given the previous application of other decoding parameters in said listing, wherein attempts to extract digital watermark data from a new image can successively apply parameters from said ranked listing until said limited time interval elapses.

2. The method of claim 1 that further includes the acts:
capturing an image frame with said camera;
processing the captured image frame with a first set of parameters from said ranked listing, to yield a first processed image excerpt;
attempting to extract digital watermark data from said first processed image excerpt; and
upon failure to successfully extract digital watermark data from said first processed image excerpt:
processing the captured image frame with a next set of parameters from said ranked listing, to yield a second processed image excerpt; and
attempting to extract digital watermark data from said second processed image excerpt.

3. The method of claim 1 in which:
act (a) includes, for one sub-part of one image frame, applying at least M different values of tilt angle-correction, and for each such value, applying R different values of bearing-angle correction, in attempting to extract digital watermark data from M*R resultant tilt angle- and bearing angle-corrected counterparts of said one sub-part of said one image frame, where M>1 and R>1;
act (b) includes performing act (a) at least N times, each with a differently-located sub-part of said one image frame, where N>1, wherein extraction of digital watermark data from said one image frame is attempted for at least M*R*N combinations of tilt angle correction values, bearing angle correction values, and sub-part locations; and
act (d) includes determining which single combination of tilt angle correction value, bearing angle correction value, and sub-part location resulted in successful extraction of digital watermark data from a greatest number of said image frames in said set P; adding this combination of tilt angle correction value, bearing angle correction value and sub-part location to a listing of decoding parameters; and removing, from the set P, those image frames from which digital watermark data was successfully extracted using said combination of tilt angle correction value, bearing angle correction value and sub-part location.

4. The method of claim 3 in which:
act (a) includes, for one sub-part of one image frame, applying at least M different values of tilt angle-correction, and for each such value of tilt angle-correction, applying R different values of bearing angle-correction, and for each such value of bearing angle-correction, applying S different values of camera model -correction, in attempting to extract digital watermark data from M*R*S resultant tilt angle-, bearing angle- and camera model-corrected counterparts of said one sub-part of said one image frame, where M>1, R>1 and S>1; and
act (b) includes performing act (a) at least N times, each with a differently-located sub-part of said one image frame, where N>1, wherein extraction of digital watermark data from said one image frame is attempted for at least M*R*S*N combinations of tilt angle correction values, bearing angle correction values, and sub-part locations; and
act (d) includes determining which single combination of tilt angle correction value, camera model values, and sub-part location resulted in successful extraction of digital watermark data from a greatest number of said image frames in said set P; adding this combination of tilt angle correction value, camera model values and sub-part location to a listing of decoding parameters; and removing, from the set P, those image frames from which digital watermark data was successfully extracted using said combination of tilt angle correction value, camera model values and sub-part location.

5. The method of claim 1 in which:
act (a) includes, for one sub-part of one image frame, applying at least M different values of tilt angle-correction, and for each such value of tilt angle-correction, applying S different values of camera model-correction, in attempting to extract digital watermark data from M*S resultant tilt angle- and camera model-corrected counterparts of said one sub-part of said one image frame, where M>1 and S>1;
act (b) includes performing act (a) at least N times, each with a differently-located sub-part of said one image frame, where N>1, wherein extraction of digital watermark data from said one image frame is attempted for at least M*S*N combinations of tilt angle correction values, bearing angle correction values, and sub-part locations.

6. A method employing a camera scanning system at a retail checkout, comprising the acts:
storing reference images captured by the camera scanning system, as a person operates the system by moving products past a window thereof;
determining, from analysis of plural of said stored reference images, a set cover-based list, the list comprising at least first and second sets of one or more watermark decoding parameters found useful in extracting digital watermark data from said reference images, so that said sets of watermark decoding parameters can be tried in extracting digital watermark data from future imagery produced by the scanning system;
the first set of watermark decoding parameters identifying a first patch of pixels to be examined in the future imagery digital watermark data;
the second set of watermark decoding parameters identifying a second patch of pixels to be examined in the future imagery for digital watermark data;
the first set of watermark decoding parameters including data specifying a location of said first patch of pixels in an image frame, a size of said first patch of pixels, a tilt of said first patch of pixels, and/or a bearing of said first patch of pixels;
the second set of watermark decoding parameters including data specifying a location of said second patch of pixels in an image frame, a size of said second patch of pixels, a tilt of said second patch of pixels, and/or a bearing of said second patch of pixels;
the first and second sets of watermark decoding parame

Assignees

• Digimarc Corp

Inventors

• Evans Eric D
• Filler Tomas

Classifications

• G06V30/1916

  Validation; Performance evaluation · CPC title

• G06F18/217

  Validation; Performance evaluation; Active pattern learning techniques · CPC title

• G06V10/464

  using a plurality of salient features, e.g. bag-of-words [BoW] representations · CPC title

• G06V30/224

  of printed characters having additional code marks or containing code marks · CPC title

• G06V10/20

  Image preprocessing · CPC title