Real time handwriting recognition system

A handwritten character recognition system for use in a data processing system including a tablet and pen for user entry of handwritten characters and a processing unit connected from the tablet and pen for operating upon the user input under control of the character recognition system, the handwritten character recognition system comprising:

• a pen input detector for detecting and indicating user inputs through the tablet and pen, the user inputs including pen strokes and pen states,
• an input cluster buffer connected from the pen input detector for storing stroke descriptor information of a current stroke as the current stroke is entered by the user,
• a point buffer connected ftom the input cluster buffer for storing the stroke descriptor information of the current stroke,
• a point detector connected from the input cluster buffer and responsive to the pen states for transferring the stroke descriptor information of the current stroke into the point buffer,
• a stroke feature recognizer connected from the point buffer and responsive to the pen states for extracting stroke recognition features from the stroke descriptor information of the current stroke and assigning a meaning to the current stroke, and
• a cluster recognizer connected from the stroke feature recognizer and responsive to the meaning assigned to each stroke for recognizing and assigning a character meaning to a current cluster of strokes,
• wherein the stroke feature recognizer includes
• a multiple scale stroke representation generator for
• reading the stroke recognition features from the stroke recognition feature data structure,
• generating a plurality of scaled topological representations of the current stroke,
• each scaled topological representation being a progressively smoothed representation of the current stroke generated from the stroke representation features,
• selecting a scaled topological representation of the current stroke, the scaled topological representation of the current stroke being selected to provide the maximum signal to noise ratio of the stroke representation,
• a stroke proportion discriminator responsive to the scaled topological representation of the current stroke for storing a list of ideal prototype representations corresponding to possible meanings of the current stroke from a plurality of ideal prototype representations of strokes, and
• a stroke boundary discriminator responsive to the scaled topological representation of the current stroke and to the ideal prototype representations of the list of ideal prototype representations for comparing the scaled topological representation of the current stroke and
• boundaries of the ideal prototype representations of the list of ideal prototype representations wherein the boundaries of the ideal prototype representations are determined by linear combinations of features of the ideal prototype representations, and
• assigning to the current stroke an identification of an ideal prototype representation having boundaries including the scaled topological representation of the current stroke, the assigned identification of the matching ideal prototype representation representing a stroke meaning assigned to the current stroke.

A handwritten character recognition system for use in a data processing systern including a tablet and pen for user entry of handwritten characters and a processing unit connected from the tablet and pen for operating uDon the user input under control of the character recognition system, the handwritten character recognition system comprising:

• a pen input detector for detecting and indicating user inputs through the tablet and pen, the user inputs including pen strokes and pen states,
• an input cluster buffer connected from the pen input detector for storing stroke descriptor information of a current stroke as the current stroke is entered by the user,
• a point buffer connected from the input cluster buffer for storing the stroke descriptor information of the current stroke,
• a point detector connected from the input cluster bufer and responsive to the pen states for transferring the stroke descritor informration of the current stroke into the point buffer,
• a stroke feature recognizer including a dynamic stroke feature extractor connected from the point buffer and responsive to a pen down state for dynamically extracting stroke recognition features from the stroke descriptor information of the current stroke as the current stroke is entered by the user and for assiliini a meaning to the current stroke, and
• a cluster recognizer connected from the stroke feature recognizer and responsive to the meaning assigned to each stroke for recognizing and assigning a character meaning to a current cluster of strokes,
• wherein the stroke feature recognizer is responsive to the stroke recognition features for assigning a meaning to each current stroke and the cluster recognizer includes
• a stroke buffer, including
• a current stroke buffer for storing the strokes of a current cluster of strokes in the time order of their entry, and
• a previous stroke buffer for storing the strokes of a cluster of strokes immediately preceding the current cluster of strokes,
• a window buffer for storing a contiguous group of strokes in spatial order according to the coordinates of the strokes of the group,
• a stroke buffer controller responsive to the stroke feature recognizer for constructing an influence list containing an identification of an area of influence of each stroke of the current cluster of strokes,
• receiving a current stroke,
• determining an area of influence of the current stroke, when the area of influence of the current stroke indicates that the current stroke is a part of the current cluster of strokes,
• writing the current stroke into the current stroke buffer, and
• when the area of influence of the current stroke indicates that the current stroke is not a part of the current cluster of strokes,
• transferring the strokes of the current cluster of strokes into the previous stroke buffer, and
• writing the current stroke into the current stroke buffer to begin a new current cluster of strokes,
• a stroke buffer scanner for scanning the influence list, and
• writing the strokes of the current stoke buffer into the window buffer in spatial order,
• a position discriminator for storing a cluster data structure containing a plurality of cluster meanings,
• each cluster meaning representing a cluster of strokes and a corresponding meaning assigned to the cluster of strokes,
• reading combinations of strokes from the window buffer,
• comparing the combinations of strokes from the window buffer with the cluster meanings stored in the cluster data structure,
• determining when a combination a strokes from the window buffer corresponds to a cluster meaning,
• providing as an output an identification of the cluster meaning corresponding to the combination of strokes from the window buffer,
• removing the combination of strokes from the window buffer, and transferring the combination of strokes fom the current cluster buffer to the previous stroke buffer.

In a data processing system including a tablet and pen for user entry of handwritten characters and a processing unit connected from the tablet and pen for operating upon the user input, a method for recognizing handwritten characters, comprising the steps of:

• storing stroke descriptor information of a current stroke in a stroke buffer as the current stroke is entered by the user,
• responsive to the pen states, transferring the stroke descriptor information of the current stroke into a point buffer,
• in response to a pen down state, dynamically extracting stroke recognition features from the stroke descriptor information of the current stroke and dynamically assigning a meaning to the current stroke,
• wherein the stroke recognition features describe the current stroke with variable degrees of hierarchical aIproximations, the hierarchical approximations including mutiple scalar representations of the current stroke, and
• recognizing and assigning a character meaning to a current cluster of strokes.

In a data processing system including a tablet and pen for user entry of handwritten characters and a processing unit connected from the tablet and pen for operating upon the user input, a method for recognizing handwritten characters. comprising the steps of:

• storing stroke descriptor information of a current stroke in a stroke buffer as the current stroke is entered by the user,
• responsive to the pen states, transferring the stroke descriptor information of the current stroke into a point buffer,
• extracting stroke recognition features from the stroke descriptor information of the current stroke and assigning a meaning to the current stroke, and
• recognizing and assigning a character meaning to a current cluster of strokes, including
• reading the stroke recognition features from the stroke recognition feature data structure,
• generating a plurality of scaled topological representations of the current stroke,
• each scaled topological representation being a progressively smoothed representation of the current stroke generated from the stroke representation features,
• selecting a scaled topological representation of the current stroke, the scaled topological representation of the current stroke being selected to provide the maximum signal to noise ratio of the stroke representation,
• storing a list of ideal prototype representations corresponding to possible meanings of the current stroke from a plurality of ideal prototype representations of strokes,
• comparing the scaled topological representation of the current stroke and boundaries of the ideal prototype representations of the list of ideal prototype representations wherein the boundaries of the ideal prototype representations are determined by linear combinations of features of the ideal prototype representations, and
• assigning to the current stroke an identification of an ideal prototype representation having boundaries including the scaled topological representation of the current stroke, the assigned identification of the matching ideal prototype representation representing a stroke meaning assigned to the current stroke.