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EP0279158A2
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Method and apparatus for recognition of graphic symbols
Assignee: GTX Corp
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Filing: 1988-01-05
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Granted: —
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Expires: 2008-01-05
Abstract
Abstract A technique for recognizing hand-drawn graphic symbols operates on vectorized graphic data, including lines, arcs, and circles, that have been produced by an automatic drawing recognition system. The user creates segmented rule bases for recognizing various symbols by describing the geometric structures of recognizable symbols and subsymbols. The rule bases each are compiled into a respective decision tree. Fetched input vectors and entities are placed in software "blackboards", and more particularly, into appropriate symbol slots and subsymbol slots thereof. The growing symbol and subsymbols on the blackboards are continually restructured until they form closed loops or the blackboards are filled. The decision tree then is applied to all possible permutations of the symbols and/or subsymbols to accomplish partial or complete recognition. An inference engine subsystem controls application of the decision trees to limited bits of the symbols and subsymbols, matching decision subtree segment labels to attributes associated with the blackboard data, and orders the matched data according to degree of matching to effectuate application of the decision tree to the linked lists.
Inventors
- 👤 Parvathy Bhaskaran
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 16:11
CPC Classifications
G; G06; G06V; G06V30/00; G06V30/10; G06V30/24; G06V30/248; G06V30/2504; G06V30/40; G06V30/42; G06V30/422
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
115 words
In a computerized graphics system, a symbol recognition system comprising in combination: (a) a list of stored vectors produced by vectorizing a drawing or the like, including vectors of the graphic symbol to be recognized; (b) means for storing a rule base decision tree including a plurality of geometric tests for various features of the graphic symbol; (c) means for forming a linked list of vectors representative of features of the graphic symbol; and (d) means for performing sequences of the geometric tests on selected portions of the linked list at successive nodes of the decision tree and producing a symbol identifier corresponding to the graphic symbol if a predetermined outcome of the tests occurs.
Claim 2
Dependent Claim
115 words
In a computerized graphics system, a symbol recognition system comprising in combination: (a) a list of stored vectors produced by vectorizing a drawing or the like, including vectors of the graphic symbol to be recognized; (b) means for storing a rule base decision tree including a plurality of geometric tests for various features of the graphic symbol; (c) means for forming a linked list of vectors representative of features of the graphic symbol; and (d) means for performing sequences of the geometric tests on selected portions of the linked list at successive nodes of the decision tree and producing a symbol identifier corresponding to the graphic symbol if a predetermined outcome of the tests occurs.
Claim 3
Dependent Claim
43 words
The symbol recognition system of Claim 1 including means for defining a window that surrounds a relatively small region of the drawing containing the graphic symbol, wherein linked list forming means includes means for selecting a software blackboard that corresponds to the window.
Claim 4
Dependent Claim
55 words
The symbol recognition system of Claim 2 wherein the linked list forming means includes means for fetching a vector from the list of stored vectors and means for inserting the vector into a symbol slot in the blackboard, the symbol slot having locational parameters that correspond to the location of the vector in the window.
Claim 5
Dependent Claim
49 words
The symbol recognition system of Claim 3 wherein the linked list forming means includes means for inserting the vector in a subsymbol slot in the symbol slot, and means for adding the vector to a linked list including a vector already in the subsymbol slot if there is one.
Claim 6
Dependent Claim
68 words
The symbol recognition system of Claim 4 wherein the linked list forming means includes means for creating the subsymbol slot if there does not already exist a previous subsymbol slot into which the vector can be inserted, means for inserting the vector into the created subsymbol slot, and means for adding the created subsymbol slot to a linked list of subsymbol slots that includes the previous subsymbol slot.
Claim 7
Dependent Claim
72 words
The symbol recognition system of Claim 5 wherein the linked list forming means includes means for creating a plurality of subsymbol slots in the course of fetching a plurality of vectors from the list of stored vectors and inserting the subsymbol slots into the symbol slot, means for determining if certain portions of subsymbols in various subsymbol slots are sufficiently close to be merged, and if so, means for merging such subsymbols.
Claim 8
Dependent Claim
48 words
The symbol recognition system of Claim 6 wherein the geometric test sequence performing means includes means for determining whether any types of subsymbols included in the linked list of subsymbol slots occur more than once, and if so, determining the number of possible permutations of the recurring subsymbols.
Claim 9
Dependent Claim
61 words
The symbol recognition system of Claim 6 wherein the geometric test sequence performing means includes means for updating a guess variable with a symbol identifier at each node of the decision tree if the outcome of the sequence of geometric tests at that node has a predetermined outcome and that node of the decision tree has a symbol identifier associated therewith.
Claim 10
Dependent Claim
85 words
The symbol recognition system of Claim 1 wherein the decision tree includes a plurality of nodes, the geometric test sequence performing means includes means for performing a different sequence of geometric tests on the linked list at each node of the decision tree, each sequence of geometric tests having an outcome that is true or false depending on which subsymbol slots or symbol slots are contained in the linked list, each true outcome determining which node of the decision tree is to be traversed next.
Claim 11
Dependent Claim
76 words
The symbol recognition system of Claim 9 including means for backtracking if no further permutations of the linked list are possible and no true outcome is obtained for the present node, the backtracking means including means for traversing the node of the decision tree pointed to by the false outcome of the last sequence of geometric tests and performing a new sequence of the geometric tests of that node on a portion of the linked list.
Claim 12
Dependent Claim
45 words
The symbol recognition of Claim 9 including means for determining certain attributes of the linked list and comparing the linked list attributes to attributes of portions of the decision tree to select portions of the decision tree against which the linked list can be tested.
References Cited (Backward Citations)
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