EP0633548A2
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EP
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Method and device for determining a contour in a space having a density distribution
Assignee: Koninklijke Philips NV
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Filing: 1994-06-22
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Granted: —
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Expires: 2014-06-22
Abstract
Abstract In a space having a density variation of a certain parameter, a contour (10) is defined consisting of vertices (11, 12, 13) connected by edges (14, 15, 16). By variation of the position and number of the vertices as a function of the density variation in the space, the contour (10) is determined to follow features in the density variation. The movement of vertices is restricted to a direction ( i )perpendicular to the local direction ( i ) of the contour (10). For smoothening the contour (10), an internal force or energy is applied to each of the vertices (11, 12, 13) which force or energy depends on the angle ( c i ) between the edges at the vertex, or of the variation of the angles along a sequence of adjacent vertices. A direct interaction between vertices is thereby avoided.
Inventors
- 👤 Steven Lobregt
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 16:02
CPC Classifications
G; G06; G06T; G06T7/00; G06T7/0002; G06T7/0012; G06T7/10; G06T7/12; G06T2207/00; G06T2207/10; G06T2207/10132; G06T2207/20; G06T2207/20092; G06T2207/20096; G06T2207/30; G06T2207/30004; G06T2207/30101
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
148 words
Method for determining a contour in a space with a density variation, comprising: defining a plurality of initial vertices being located on a seed contour, said vertices being connected by edges to neighbouring vertices; defining an energy function comprising an internal portion which is a function of the curvature at each of the vertices and an external portion determined by the density variation at the location of each of said vertices; determining a final contour by continuously varying the position of the vertices till the energy function reaches a minimum, characterised in that, for each of the vertices the internal portion of the energy function is dependent on the angle between the edges at the respective vertex and in that the external portion of the energy function is related to the density variation in a direction having equal angles with each of the edges at the respective vertex.
Claim 2
Dependent Claim
28 words
Method according to claim 1, characterised in that the internal energy portion is derived from the difference in angles of the edges at a series of adjacent vertices.
Claim 3
Dependent Claim
35 words
Method according to claim 2, characterised in that said internal energy portion is obtained by the convolution of said difference in angles with a symmetric discrete filter having a zero frequency component equal to zero.
Claim 4
Dependent Claim
16 words
Method according to claim 1, 2 or 3, characterised in that the seed contour is open.
Claim 5
Dependent Claim
38 words
Method according to claim 1, 2, 3 or 4, characterised in that if during minimization of the energy function an edge length exceeds a first predetermined threshold, the edge is replaced by an additional vertex and connecting edges.
Claim 6
Dependent Claim
41 words
Method according to claim 1, 2, 3, 4 or 5, characterised in that if during minimization of the energy function an edge length falls below a second predetermined threshold, the edge and the connected vertices are replaced by a single vertex.
Claim 7
Dependent Claim
27 words
Method according to any one of the preceding claims, characterised in that a user defined energy distribution is added to the external portion of the energy function.
Claim 8
Dependent Claim
64 words
Method according to claim 1, characterised in that firstly a contour is determined in a first space and that, secondly, a contour is determined in a second space having a density variation having similar features to the density variation in the first space whereby the seed contour in the second space is defined by transfer of the final contour obtained in the first space.
Claim 9
Dependent Claim
202 words
Arrangement for determining a contour a space in which a given parameter has a value varying throughout said space, the arrangement comprising - a memory (12) for storing parameter values in said space in the form of a matrix of pixel values; - a display (11) having a two-dimensional matrix of pixels; - pointer means for indicating initial vertex positions for the definition of a seed contour; - computing means (13), having access to said memory (12) and said vertex positions, for evaluating an energy function comprising an internal portion which is a function of the curvature at each of the vertices and an external portion determined by the density variation at the location of each of said vertices; the computing means being arranged for - determining a final contour by continuously varying the position of the vertices till the energy function reaches a minimum, while - for each of the vertices the internal portion of the energy function is dependent on the angle between the edges at the respective vertex and in that the external portion of the energy function is related to the density variation in a direction having equal angles with each of the edges at the respective vertex.
References Cited (Backward Citations)
No citation records indexed.
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