Feature Extraction And Use With A Probability Density Function (PDF) Divergence Metric

• US 20140023278A1
• Filed: 03/07/2013
• Published: 01/23/2014
• Est. Priority Date: 07/19/2012
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Krishna Kumar, Raj Kumar, Baheti, Pawan Kumar, Gore, Dhananjay Ashok
• Granted Patent: US 9,141,874 B2
• Time in Patent Office: Days
• US Class Current: 382/192
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/18095 Summing image-intensity values; Projection and histogram analysis

Abstract

An image of real world is processed to identify blocks as candidates to be recognized. Each block is subdivided into sub-blocks, and each sub-block is traversed to obtain counts, in a group for each sub-block. Each count in the group is either of presence of transitions between intensity values of pixels or of absence of transition between intensity values of pixels. Hence, each pixel in a sub-block contributes to at least one of the counts in each group. The counts in a group for a sub-block are normalized, based at least on a total number of pixels in the sub-block. Vector(s) for each sub-block including such normalized counts may be compared with multiple predetermined vectors of corresponding symbols in a set, using any metric of divergence between probability density functions (e.g. Jensen-Shannon divergence metric). Whichever symbol has a predetermined vector that most closely matches the vector(s) is identified and stored.

Claims

1. A method of symbol recognition, the method comprising:

receiving a portion of an image of a scene of real world;

traversing at least the portion of the image to;

identify changes in intensities of pixels in the image; and

generate a group of counts based on the changes, without encoding positions at which the changes occur in the image;

wherein an intensity of each pixel in the portion of the image is used to generate at least one count in the group of counts;

wherein a size of the group of counts is predetermined;

wherein at least a first count in the group of counts is incremented, when an intensity change between two pixels, in a direction of traversal, exceeds a predetermined threshold;

wherein at least a second count in the group of counts is incremented, when the intensity change is positive and the intensity change does not exceed the predetermined threshold;

using a measure of difference between two probability distributions, to compare a vector that is based on at least the group of counts with a plurality of predetermined vectors of corresponding symbols in a set, to identify a specific symbol therein; and

storing the specific symbol in a memory, as being recognized in the image;

wherein the memory is coupled to one or more processors; and

wherein the traversing and the using are performed by the one or more processors.

2. The method of claim 1 wherein the portion is hereinafter referred to as a sub-block, and the sub-block is one of a plurality of sub-blocks comprised in a block in the image, the method further comprising:

dividing the block in the image to obtain the plurality of sub-blocks; and

assembling the vector by appending to one another, a plurality of groups of counts including said group of counts generated by the traversing;

wherein the plurality of groups of counts are obtained from the plurality of sub-blocks, by repeating the traversing; and

wherein the plurality of groups of counts are appended in a predetermined order, to obtain the vector.

3. The method of claim 2 wherein:

the block is identified by use of a predetermined test; and

the predetermined test is to detect pixels in the image that form a shiro-rekha;

wherein the shiro-rekha connects a plurality of tops of characters, of a word in Devanagari.

4. The method of claim 1 further comprising:

the one or more processors dividing each count in the group of counts by at least a total number of pixels N in the portion of the image.

5. The method of claim 1 wherein:

the portion is traversed multiple times in multiple directions respectively.

6. The method of claim 1 wherein:

the first count is incremented during the traversing when the direction of traversal is a predetermined first direction;

the second count is incremented during the traversing when the direction of traversal is the predetermined first direction;

a third count in the group of counts is incremented during the traversing when the intensity change, in the predetermined first direction, is negative and an absolute value thereof exceeds the predetermined threshold;

wherein a predetermined second direction is perpendicular to the predetermined first direction;

a fourth count in the group of counts is incremented during the traversing when the direction of traversal is the predetermined second direction, and the intensity change does not exceed the predetermined threshold;

a fifth count in the group of counts is incremented during the traversing when the direction of traversal is the predetermined second direction, and the intensity exceeds the predetermined threshold; and

a sixth count in the group of counts is incremented during the traversing when the intensity change, in the predetermined second direction, is negative and the absolute value thereof exceeds the predetermined threshold.

7. The method of claim 1 wherein:

the first count is incremented during the traversing when the direction of traversal is a predetermined first direction;

the second count is incremented during the traversing when the direction of traversal is the predetermined first direction;

a third count in the group of counts is incremented during the traversing when the intensity change, in the predetermined first direction, is negative and an absolute value thereof exceeds the predetermined threshold;

a fourth count is incremented during the traversing when the intensity change, in the predetermined first direction, is negative and the absolute value thereof does not exceed the predetermined threshold;

wherein a predetermined second direction is perpendicular to the predetermined first direction;

a fifth count in the group of counts is incremented during the traversing when the direction of traversal is the predetermined second direction, and the intensity change does not exceed the predetermined threshold;

a sixth count in the group of counts is incremented during the traversing when the direction of traversal is the predetermined second direction, and the intensity exceeds the predetermined threshold;

a seventh count in the group of counts is incremented during the traversing when the intensity change, in the predetermined second direction, is negative and the absolute value thereof exceeds the predetermined threshold; and

an eighth count is incremented during the traversing when the intensity change, in the predetermined second direction, is negative and the absolute value thereof does not exceed the predetermined threshold.

8. The method of claim 1 wherein:

the intensities of pixels in the image are binarized;

the predetermined threshold is 0;

the first count is incremented during the traversing when the direction of traversal is a predetermined first direction, and the intensity change between said two pixels is from a first intensity of binary value 0 to a second intensity of binary value 1;

the second count is incremented during the traversing when the intensity change, in the predetermined first direction, is non-existent and the intensity of each of said two pixels is identical, of binary value 0 or 1;

a third count in the group of counts is incremented during the traversing when the direction of traversal is the predetermined first direction, and the intensity change between said two pixels is from the second intensity of binary value 1 to the first intensity of binary value 0;

wherein a predetermined second direction is perpendicular to the predetermined first direction;

a fourth count in the group of counts is incremented during the traversing when the intensity change, in the predetermined second direction, is non-existent and the intensity of each of said two pixels is identical, of binary value 0 or 1;

a fifth count in the group of counts is incremented during the traversing when the direction of traversal is the predetermined second direction, and the intensity change between said two pixels is from the first intensity of binary value 0 to the second intensity of binary value 1; and

a sixth count in the group of counts is incremented during the traversing when the direction of traversal is the predetermined second direction, and the intensity change between said two pixels is from the second intensity of binary value 1 to the first intensity of binary value 0.

9. The method of claim 1 wherein:

the intensities of pixels in the image are binarized;

the predetermined threshold is 0;

the first count is incremented during the traversing when the direction of traversal is a predetermined first direction, and the intensity change between said two pixels is from binary value 0 to binary value 1;

the second count is incremented during the traversing when the intensity change, in the predetermined first direction, is non-existent and the intensity of each of said two pixels is identical to binary value 0;

a third count is incremented during the traversing when the intensity change, in the predetermined first direction, is non-existent and the intensity of each of said two pixels is identical to binary value 1;

a fourth count in the group of counts is incremented during the traversing when the direction of traversal is the predetermined first direction, and the intensity change between said two pixels is from binary value 1 to binary value 0;

wherein a predetermined second direction is perpendicular to the predetermined first direction;

a fifth count in the group of counts is incremented during the traversing when the intensity change, in the predetermined second direction, is non-existent and the intensity of each of said two pixels is identical to binary value 0;

a sixth count in the group of counts is incremented during the traversing when the intensity change, in the predetermined second direction, is non-existent and the intensity of each of said two pixels is identical to binary value 1;

a seventh count in the group of counts is incremented during the traversing when the direction of traversal is the predetermined second direction, and the intensity change between said two pixels is from binary value 0 to binary value 1; and

a eighth count in the group of counts is incremented during the traversing when the direction of traversal is the predetermined second direction, and the intensity change between said two pixels is from binary value 1 to binary value 0.

10. The method of claim 1 wherein the specific symbol is at least one of:

a predetermined logo;

a traffic sign;

or

a predetermined letter of an alphabet written in a predetermined font.

11. The method of claim 1 wherein said using of the measure of difference comprises:

computing a plurality of values of the measure of difference, respectively between said vector and said plurality of predetermined vectors of corresponding symbols; and

identifying a value among the plurality of values for being smallest;

wherein a predetermined vector, of the specific symbol identified as being recognized in the image, is used in said computing of the value identified as being smallest.

12. The method of claim 1 wherein:

wherein a predetermined vector of the specific symbol is hereinafter P and the vector for said portion of the image is hereinafter Q, the method further comprising;

computing a mean vector as

13. A mobile device to perform symbol recognition, the mobile device comprising:

one or more memories comprising a plurality of portions identified from an image of a scene of real world, as candidates to be recognized;

one or more processors configured to traverse at least one portion of the image to;

identify changes in intensities of pixels in the image; and

generate a group of counts based on the changes, without encoding positions at which the changes occur in the image;

wherein an intensity of each pixel in the at least one portion of the image is used to generate at least one count in the group of counts;

wherein a size of the group of counts is predetermined;

wherein at least a first count in the group of counts is incremented, when an intensity change between two pixels, in a direction of traversal, exceeds a predetermined threshold;

wherein at least a second count in the group of counts is incremented, when the intensity change is positive and the intensity change does not exceed the predetermined threshold;

wherein the one or more processors are configured to use a measure of difference between two probability distributions, to compare a vector based on at least the group of counts with a plurality of predetermined vectors of corresponding symbols in a set, to identify a specific symbol therein; and

wherein the one or more processors are configured to store the specific symbol in a memory, as being recognized in the image;

wherein the memory is coupled to the one or more processors.

14. The mobile device of claim 13 wherein:

the first count is incremented by the one or more processors during the traversing when the direction of traversal is a predetermined first direction;

the second count is incremented by the one or more processors during the traversing when the direction of traversal is the predetermined first direction;

a third count in the group of counts is incremented by the one or more processors during the traversing when the intensity change, in the predetermined first direction, is negative and an absolute value thereof exceeds the predetermined threshold;

wherein a predetermined second direction is perpendicular to the predetermined first direction;

a fourth count in the group of counts is incremented by the one or more processors during the traversing when the direction of traversal is the predetermined second direction, and the intensity change does not exceed the predetermined threshold;

a fifth count in the group of counts is incremented by the one or more processors during the traversing when the direction of traversal is the predetermined second direction, and the intensity exceeds the predetermined threshold; and

a sixth count in the group of counts is incremented by the one or more processors during the traversing when the intensity change, in the predetermined second direction, is negative and the absolute value thereof exceeds the predetermined threshold.

15. The mobile device of claim 13 wherein:

the first count is incremented by the one or more processors during the traversing when the direction of traversal is a predetermined first direction;

the second count is incremented by the one or more processors during the traversing when the direction of traversal is the predetermined first direction;

a third count in the group of counts is incremented by the one or more processors during the traversing when the intensity change, in the predetermined first direction, is negative and an absolute value thereof exceeds the predetermined threshold;

a fourth count is incremented by the one or more processors during the traversing when the intensity change, in the predetermined first direction, is negative and the absolute value thereof does not exceed the predetermined threshold;

wherein a predetermined second direction is perpendicular to the predetermined first direction;

a fifth count in the group of counts is incremented by the one or more processors during the traversing when the direction of traversal is the predetermined second direction, and the intensity change does not exceed the predetermined threshold;

a sixth count in the group of counts is incremented by the one or more processors during the traversing when the direction of traversal is the predetermined second direction, and the intensity exceeds the predetermined threshold;

a seventh count in the group of counts is incremented by the one or more processors during the traversing when the intensity change, in the predetermined second direction, is negative and the absolute value thereof exceeds the predetermined threshold; and

an eighth count is incremented by the one or more processors during the traversing when the intensity change, in the predetermined second direction, is negative and the absolute value thereof does not exceed the predetermined threshold.

16. The mobile device of claim 13 wherein:

the intensities of pixels in the image are binarized;

the predetermined threshold is 0;

the first count is incremented by the one or more processors during the traversing when the direction of traversal is a predetermined first direction, and the intensity change between said two pixels is from a first intensity of binary value 0 to a second intensity of binary value 1;

the second count is incremented by the one or more processors during the traversing when the intensity change, in the predetermined first direction, is non-existent and the intensity of each of said two pixels is identical, of binary value 0 or 1;

a third count in the group of counts is incremented by the one or more processors during the traversing when the direction of traversal is the predetermined first direction, and the intensity change between said two pixels is from the second intensity of binary value 1 to the first intensity of binary value 0;

wherein a predetermined second direction is perpendicular to the predetermined first direction;

a fourth count in the group of counts is incremented by the one or more processors during the traversing when the intensity change, in the predetermined second direction, is non-existent and the intensity of each of said two pixels is identical, of binary value 0 or 1;

a fifth count in the group of counts is incremented by the one or more processors during the traversing when the direction of traversal is the predetermined second direction, and the intensity change between said two pixels is from the first intensity of binary value 0 to the second intensity of binary value 1; and

a sixth count in the group of counts is incremented by the one or more processors during the traversing when the direction of traversal is the predetermined second direction, and the intensity change between said two pixels is from the second intensity of binary value 1 to the first intensity of binary value 0.

17. The mobile device of claim 13 wherein:

the intensities of pixels in the image are binarized;

the predetermined threshold is 0;

the first count is incremented by the one or more processors during the traversing when the direction of traversal is a predetermined first direction, and the intensity change between said two pixels is from binary value 0 to binary value 1;

the second count is incremented by the one or more processors during the traversing when the intensity change, in the predetermined first direction, is non-existent and the intensity of each of said two pixels is identical to binary value 0;

a third count is incremented by the one or more processors during the traversing when the intensity change, in the predetermined first direction, is non-existent and the intensity of each of said two pixels is identical to binary value 1;

a fourth count in the group of counts is incremented by the one or more processors during the traversing when the direction of traversal is the predetermined first direction, and the intensity change between said two pixels is from binary value 1 to binary value 0;

wherein a predetermined second direction is perpendicular to the predetermined first direction;

a fifth count in the group of counts is incremented by the one or more processors during the traversing when the intensity change, in the predetermined second direction, is non-existent and the intensity of each of said two pixels is identical to binary value 0;

a sixth count in the group of counts is incremented by the one or more processors during the traversing when the intensity change, in the predetermined second direction, is non-existent and the intensity of each of said two pixels is identical to binary value 1;

a seventh count in the group of counts is incremented by the one or more processors during the traversing when the direction of traversal is the predetermined second direction, and the intensity change between said two pixels is from binary value 0 to binary value 1; and

a eighth count in the group of counts is incremented by the one or more processors during the traversing when the direction of traversal is the predetermined second direction, and the intensity change between said two pixels is from binary value 1 to binary value 0.

18. One or more non-transitory storage media comprising instructions, which, when executed in a mobile device, cause one or more processors in the mobile device to perform operations, the instructions comprising:

instructions to receive a portion of an image of a scene of real world;

instructions to traverse at least the portion of the image to;

identify changes in intensities of pixels in the image; and

generate a group of counts based on the changes, without encoding positions at which the changes occur in the image;

wherein an intensity of each pixel in the portion of the image is used to generate at least one count in the group of counts;

wherein a size of the group of counts is predetermined;

wherein at least a first count in the group of counts is incremented, when an intensity change between two pixels, in a direction of traversal, exceeds a predetermined threshold;

wherein at least a second count in the group of counts is incremented, when the intensity change is positive and the intensity change does not exceed the predetermined threshold;

instructions to use a measure of difference between two probability distributions, to compare a vector based on at least the group of counts with a plurality of predetermined vectors of corresponding symbols in a set, to identify a specific symbol therein; and

instructions to store the specific symbol in a memory, as being recognized in the image;

wherein the memory is coupled to the one or more processors.

19. The one or more non-transitory storage media of claim 18 wherein:

the first count is incremented by execution of instructions to traverse when the direction of traversal is a predetermined first direction;

the second count is incremented by execution of instructions to traverse when the direction of traversal is the predetermined first direction;

a third count in the group of counts is incremented by execution of instructions to traverse when the intensity change, in the predetermined first direction, is negative and an absolute value thereof exceeds the predetermined threshold;

wherein a predetermined second direction is perpendicular to the predetermined first direction;

a fourth count in the group of counts is incremented by execution of instructions to traverse when the direction of traversal is the predetermined second direction, and the intensity change does not exceed the predetermined threshold;

a fifth count in the group of counts is incremented by execution of instructions to traverse when the direction of traversal is the predetermined second direction, and the intensity exceeds the predetermined threshold; and

a sixth count in the group of counts is incremented by execution of instructions to traverse when the intensity change, in the predetermined second direction, is negative and the absolute value thereof exceeds the predetermined threshold.

20. The one or more non-transitory storage media of claim 18 wherein:

the first count is incremented by execution of instructions to traverse when the direction of traversal is a predetermined first direction;

the second count is incremented by execution of instructions to traverse when the direction of traversal is the predetermined first direction;

a third count in the group of counts is incremented by execution of instructions to traverse when the intensity change, in the predetermined first direction, is negative and an absolute value thereof exceeds the predetermined threshold;

a fourth count is incremented by execution of instructions to traverse when the intensity change, in the predetermined first direction, is negative and the absolute value thereof does not exceed the predetermined threshold;

wherein a predetermined second direction is perpendicular to the predetermined first direction;

a fifth count in the group of counts is incremented by execution of instructions to traverse when the direction of traversal is the predetermined second direction, and the intensity change does not exceed the predetermined threshold;

a sixth count in the group of counts is incremented by execution of instructions to traverse when the direction of traversal is the predetermined second direction, and the intensity exceeds the predetermined threshold;

a seventh count in the group of counts is incremented by execution of instructions to traverse when the intensity change, in the predetermined second direction, is negative and the absolute value thereof exceeds the predetermined threshold; and

an eighth count is incremented by execution of instructions to traverse when the intensity change, in the predetermined second direction, is negative and the absolute value thereof does not exceed the predetermined threshold.

21. An apparatus for symbol recognition, the apparatus comprising:

means for receiving a portion of an image of a scene of real world;

means for traversing the portion of the image to;

identify changes in intensities of pixels in the image; and

generate a group of counts based on the changes, without encoding positions at which the changes occur in the image;

wherein an intensity of each pixel in the portion of the image is used to generate at least one count in the group of counts;

wherein a size of the group of counts is predetermined;

wherein at least a first count in the group of counts is incremented, when an intensity change between two pixels, in a direction of traversal, exceeds a predetermined threshold;

wherein at least a second count in the group of counts is incremented, when the intensity change is positive and the intensity change does not exceed the predetermined threshold;

means for using a measure of difference between two probability distributions, to compare a vector based on at least the group of counts with a plurality of predetermined vectors of corresponding symbols in a set, to identify a specific symbol therein; and

means for storing the specific symbol in a memory, as being recognized in the image;

wherein the memory is coupled to one or more processors.

22. The apparatus of claim 21 wherein:

the first count is incremented by the means for traversing when the direction of traversal is a predetermined first direction;

the second count is incremented by the means for traversing when the direction of traversal is the predetermined first direction;

a third count in the group of counts is incremented by the means for traversing when the intensity change, in the predetermined first direction, is negative and an absolute value thereof exceeds the predetermined threshold;

wherein a predetermined second direction is perpendicular to the predetermined first direction;

a fourth count in the group of counts is incremented by the means for traversing when the direction of traversal is the predetermined second direction, and the intensity change does not exceed the predetermined threshold;

a fifth count in the group of counts is incremented by the means for traversing when the direction of traversal is the predetermined second direction, and the intensity exceeds the predetermined threshold; and

a sixth count in the group of counts is incremented by the means for traversing when the intensity change, in the predetermined second direction, is negative and the absolute value thereof exceeds the predetermined threshold.

23. The apparatus of claim 21 wherein:

the first count is incremented by the means for traversing when the direction of traversal is a predetermined first direction;

the second count is incremented by the means for traversing when the direction of traversal is the predetermined first direction;

a third count in the group of counts is incremented by the means for traversing when the intensity change, in the predetermined first direction, is negative and an absolute value thereof exceeds the predetermined threshold;

a fourth count is incremented by the means for traversing when the intensity change, in the predetermined first direction, is negative and the absolute value thereof does not exceed the predetermined threshold;

wherein a predetermined second direction is perpendicular to the predetermined first direction;

a fifth count in the group of counts is incremented by the means for traversing when the direction of traversal is the predetermined second direction, and the intensity change does not exceed the predetermined threshold;

a sixth count in the group of counts is incremented by the means for traversing when the direction of traversal is the predetermined second direction, and the intensity exceeds the predetermined threshold;

a seventh count in the group of counts is incremented by the means for traversing when the intensity change, in the predetermined second direction, is negative and the absolute value thereof exceeds the predetermined threshold; and

an eighth count is incremented by the means for traversing when the intensity change, in the predetermined second direction, is negative and the absolute value thereof does not exceed the predetermined threshold.