Radical-based HMM modeling for handwritten East Asian characters
View Patent ↗Exemplary methods, systems, and computer-readable media for developing, training and/or using models for online handwriting recognition of characters are described. An exemplary method for building a trainable radical-based HMM for use in character recognition includes defining radical nodes, where a radical node represents a structural element of an character, and defining connection nodes, where a connection node represents a spatial relationship between two or more radicals. Such a method may include determining a number of paths in the radical-based HMM using subsequence direction histogram vector (SDHV) clustering and determining a number of states in the radical-based HMM using curvature scale space-based (CSS) corner detection.
1. A method for character recognition, implemented at least in part by a computing device, the method comprising:
receiving ink data for a character;
recognizing the character as associated with the received ink data using a radical-based Hidden Markov Model (HMM), the radical-based HMM comprising radical nodes, wherein a radical node represents a structural element of a character, and connection nodes, wherein a connection node represents a spatial relationship between two or more radicals; and
describing the radical-based HMM with a finite state machine that comprises at least one state selected from durative states or turning states.
2. The method of claim 1 wherein the radical-based HMM comprises a multi-path topology wherein at least some paths of the multi-path topology traverse one or more radical nodes and one or more connection nodes.
3. The method of claim 1 wherein the radical nodes represent radicals in a contextual radical set.
4. The method of claim 3 wherein the contextual radical set accounts for shape variance of radicals with respect to characters.
5. The method of claim 1 wherein the characters comprise East Asian characters.
6. A method for character recognition, implemented at least in part by a computing device, the method comprising:
receiving ink data for a character;
recognizing the character as associated with the received ink data using a radical-based Hidden Markov Model (HMM), the radical-based HMM comprising radical nodes, wherein a radical node represents a structural element of the character, and connection nodes, wherein a connection node represents a spatial relationship between two or more radicals; and
describing the radical-based HMM with a finite state machine that comprises at least one state selected from durative states or turning states, wherein a durative state represents a stroke forming action in forming the character.
7. A method for character recognition, implemented at least in part by a computing device, the method comprising:
receiving ink data for a character;
recognizing the character as associated with the received ink data using a radical-based Hidden Markov Model (HMM), the radical-based HMM comprising radical nodes, wherein a radical node represents a structural element of the character, and connection nodes, wherein a connection node represents a spatial relationship between two or more radicals; and
describing the radical-based HMM with a finite state machine that comprises at least one state selected from durative states or turning states, wherein a turning state represents a turning action in forming a character.
8. A method for training a radical-based Hidden Markov Model (HMM) for character recognition, implemented at least in part by a computing device, the method comprising:
providing an initial radical-based HMM that comprises radical nodes and connection nodes;
splitting character ink data into radical data and connection data using the initial radical-based HMM;
training radical HMMs with the radical data and training connection HMMs with the connection data;
generating a trained radical-based HMM by concatenating the trained radical HMMs and the trained connection HMMs; and
determining a number of paths for the trained radical-based HMM, wherein the determining the number of paths for the trained radical-based HMM includes using a subsequence direction histogram vector (SDHV) clustering.
9. The method of claim 8 further comprising iteratively training the radical-based HMM using the character ink data.
10. The method of claim 8 further comprising splitting character ink data into radical data and connection data using the trained radical-based HMM.
11. The method of claim 10 comprising generating a refined trained radical-based HMM using the radical data and the connection data split using the trained radical-based HMM.
12. The method of claim 8 wherein the characters comprise East Asian characters.
13. A method for training a radical-based Hidden Markov Model (HMM) for character recognition, implemented at least in part by a computing device, the method comprising:
providing an initial radical-based HMM that comprises radical nodes and connection nodes;
splitting character ink data into radical data and connection data using the initial radical-based HMM;
training radical HMMs with the radical data and training connection HMMs with the connection data;
generating a trained radical-based HMM by concatenating the trained radical HMMs and the trained connection HMMs; and
determining a number of states for the radical-based HMM, wherein the determining the number of states for the radical-based HMM comprises using a curvature scale space-based (CSS) corner detection.
14. A method for training a radical-based Hidden Markov Model (HMM) for character recognition, implemented at least in part by a computing device, the method comprising:
providing an initial radical-based HMM that comprises radical nodes and connection nodes by:
selecting a set of characters;
providing a set of radicals that can represent the characters;
providing types of connections that represent relationships between two or more radicals of the set of radicals; and
generating the initial radical-based HMM by constructing paths through nodes that represent radicals and nodes that represent types of connections using a path splitting algorithm that applies a convergence measure, wherein the convergence measure comprises self-rotation probabilities and leaving transition probabilities;
splitting character ink data into radical data and connection data using the initial radical-based HMM;
training radical HMMs with the radical data and training connection HMMs with the connection data; and
generating the trained radical-based HMM by concatenating the trained radical HMMs and the trained connection HMMs.
15. A method for training a radical-based Hidden Markov Model (HMM) for character recognition, implemented at least in part by a computing device, the method comprising:
providing an initial radical-based HMM that comprises radical nodes and connection nodes by:
selecting a set of characters;
providing a set of radicals that can represent the characters;
providing types of connections that represent relationships between two or more radicals of the set of radicals; and
generating the initial radical-based HMM by constructing paths through nodes that represent radicals and nodes that represent types of connections using a path splitting algorithm that applies a convergence measure;
splitting character ink data into radical data and connection data using the initial radical-based HMM;
training radical HMMs with the radical data and training connection HMMs with the connection data; and
generating the trained radical-based HMM by concatenating the trained radical HMMs and the trained connection HMMs.