Method and apparatus for on-top writing

Abstract

A handwriting recognition apparatus facilitates user entry of strokes one on top of another. The apparatus, which includes a processor and a display integrated with a touch sensitive screen, receives a series of strokes via the screen. Each stroke is defined by contact, trace, and lift occurrences. Each stroke appears on the display until occurrence of a prescribed event, and then disappears. The apparatus accumulates strokes into a buffer and interprets all accumulated strokes collectively against a character database and optionally a linguistic database, to identify multiple candidate strings that could be represented by the accumulated strokes. The apparatus displays candidate strings for user selection after all strokes have faded, or after receiving a user submitted delimiter, or after a given delay has elapsed following user entry of the latest stroke. Alternatively, candidate strings are displayed after each stroke without waiting for timeout or explicit delimiter.

1 . A handwriting recognition apparatus, comprising:
 a touch-sensitive display adapted to receive one or more strokes input by a user and present one or more complete candidate strings for user selection, each stroke defined by a contact, trace, and lift, and each complete candidate string representing a potential interpretation of the strokes input by the user;   a processor coupled to the touch-sensitive display and a machine-readable storage; and   the machine-readable storage comprising at least one of a character database that includes predefined character shape data and a linguistic database that includes predefined character strings, and instructions for:
 receiving the one or more strokes and accumulating the strokes into a buffer; 
 presenting each stroke on the touch-sensitive display until occurrence of a prescribed event after which the stroke disappears; 
 interpreting all or a portion of the accumulated strokes collectively to identify at least one candidate string that could potentially be represented by the accumulated strokes by:
 combining the strokes in different ways to produce alternative configurations; 
 comparing, for each alternative configuration, each stroke with the character database to produce at least one character candidate and a character distance for each character candidate; and 
 concatenating said character candidates in different combinations to produce the complete candidate strings; 
 generating a list of the complete candidate strings ordered by candidate string score; and 
 presenting on the touch-sensitive display at least one complete candidate string for user selection. 
 
   
     
     
         2 . The handwriting recognition apparatus of  claim 1 , where the candidate string score is produced by weighing the distances of the concatenated characters and string likeliness such that low scores are more likely to represent the accumulated strokes. 
     
     
         3 . The handwriting recognition apparatus of  claim 1 , where the at least one candidate string is displayed upon one of the following bases:
 (1) when all strokes have disappeared,   (2) after receiving a predefined user-submitted delimiter, or   (3) after a predetermined delay has elapsed following user entry of a most recent stroke.   
     
     
         4 . The handwriting recognition apparatus of  claim 1 , further comprising:
 interpreting all or a portion of the accumulated strokes collectively against one or both of the character database and the linguistic database to identify at least one candidate string that could potentially be represented by the accumulated strokes.   
     
     
         5 . The handwriting recognition apparatus of  claim 1 , where the order also depends on string length, such that long strings having a particular linguistic likelihood are promoted more than short strings having the particular linguistic likelihood. 
     
     
         6 . The handwriting recognition apparatus of  claim 3 , where the prescribed event comprises expiration of a prescribed time period. 
     
     
         7 . The handwriting recognition apparatus of  claim 6 , where, upon user entry of multiple strokes within a length of time less than or equal to the prescribed time period, the touch-sensitive display concurrently presents all of the strokes in various stages of fading. 
     
     
         8 . The handwriting recognition apparatus of  claim 6 , where the predetermined delay is different than the prescribed time period. 
     
     
         9 . The handwriting recognition apparatus of  claim 1 , where presenting each stroke on the touch-sensitive display until occurrence of the prescribed event after which the stroke disappears comprises:
 making an area of the touch-sensitive screen visually distinct in response to receiving stroke; and   after a prescribed time period from entry of the stroke, fading the visually distinct area.   
     
     
         10 . The handwriting recognition apparatus of  claim 1 , where the prescribed event comprises user entry of a prescribed number of subsequent strokes. 
     
     
         11 . The handwriting recognition apparatus of  claim 1 , where presenting each stroke on the touch-sensitive display until occurrence of the prescribed event after which the stroke disappears comprises:
 responsive to user entry of a new stroke, incrementally fading each currently displayed stroke by a predetermined amount.   
     
     
         12 . The handwriting recognition apparatus of  claim 1 , where the strokes form multiple characters and at least some of the characters substantially overlap each other. 
     
     
         13 . A method for recognizing handwriting on an electronic device, comprising:
 receiving one or more input strokes via a touch sensitive screen, each input stroke defined by a contact, trace, and lift;   presenting each input stroke on a display until occurrence of a prescribed event after which the input stroke disappears;   accumulating the input strokes into a buffer;   interpreting the accumulated input strokes collectively to identify at least one candidate string that could potentially be represented by the accumulated strokes by:
 combining the input strokes in different ways to produce alternative configurations; 
 comparing, for each alternative configuration, each input stroke with a character database to produce at least one character candidate and a character distance for each character candidate; 
 concatenating said character candidates in different combinations to produce one or more complete candidate strings that represent potential interpretations of user-intended strokes from start to end; and 
 generating a ranked list of the complete candidate strings that is ordered by score of each candidate string, where scores are produced by weighing the character distances of the concatenated characters and string likeliness such that candidate strings that are more likely to represent the accumulated strokes are ranked higher. 
   
     
     
         14 . The method of  claim 13 , further comprising:
 comparing, for each alternative configuration, the input strokes with the character database to produce q character candidates and a character distance for each character candidate, wherein q is a positive integer greater than or equal to two.   
     
     
         15 . The method of  claim 13 , further comprising:
 presenting on the display at least one complete candidate string for user selection, the complete candidate strings being displayed upon one of the following bases:
 (1) when all strokes have disappeared, 
 (2) after receiving a predefined user submitted delimiter, or 
 (3) after a predetermined delay has elapsed following user entry of a most recent stroke. 
   
     
     
         16 . The method  claim 13 , further comprising:
 storing predefined character shape data in the character database;   providing a linguistic database that includes predefined character strings; and   interpreting the accumulated input strokes collectively against one or both of the character database and the linguistic database to identify at least one candidate string that could potentially be represented by the accumulated strokes.   
     
     
         17 . The method of  claim 13 , where the order also depends on string length, such that long strings having a particular linguistic likelihood are promoted more than short strings having the particular linguistic likelihood. 
     
     
         18 . The method of  claim 15 , where the prescribed event comprises expiration of a prescribed time period. 
     
     
         19 . The method of  claim 18 , further comprising:
 responsive to user entry of multiple input strokes within a length of time less than or equal to the prescribed time period, concurrently presenting all of the input strokes in various stages of fading.   
     
     
         20 . The method of  claim 18 , where the predetermined delay is different than the prescribed time period. 
     
     
         21 . The method of  claim 13 , where presenting each input stroke on the display until occurrence of a prescribed event after which the input stroke disappears further comprises:
 making an area of the touch sensitive screen visually distinct in response to receiving the input stroke; and   after a prescribed time period from entry of the input stroke, fading the visually distinct area.   
     
     
         22 . The method of  claim 13 , where the prescribed event comprises user entry of a prescribed number of subsequent input strokes. 
     
     
         23 . The method of  claim 13 , where presenting each input stroke on the display until occurrence of the prescribed event after which the input stroke disappears comprises:
 responsive to user entry of a new input stroke, incrementally fading each currently displayed input stroke by a predetermined amount.   
     
     
         24 . The method of  claim 13 , where the input strokes form multiple characters and at least some of the characters substantially overlap each other. 
     
     
         25 . A handwriting recognition apparatus, comprising:
 a display having a touch-sensitive screen that is adapted to display one or more strokes input by a user, each stroke defined by a contact, trace, and lift;   a machine-readable storage comprising at least one of a character database that includes predefined character shape data and a linguistic database that includes predefined character strings; and   a processor coupled to the display and the machine-readable storage, the processor programmed to perform operations comprising:
 receiving the one or more strokes via the touch-sensitive screen; 
 removing, on the occurrence of a prescribed event, one of the strokes from the display; 
 accumulating the strokes into a buffer; 
 interpreting all or a portion of the accumulated strokes against the character database, the linguistic database, or both, to identify one or more candidate strings that could potentially be represented by the accumulated strokes by:
 combining the strokes in different ways to produce alternative configurations; 
 comparing, for each alternative configuration, each stroke with the character database to produce at least one character candidate; 
 concatenating said character candidates in different combinations to produce complete candidate strings, each complete candidate string comprising a potential representation of user-intended strokes from start to end; and 
 generating a ranked list of the complete candidate strings that is ordered by score of each candidate string, where scores are produced by weighing string likeliness such that candidate strings that are more likely to represent the accumulated strokes are ranked higher.