计算机视觉课件(1).ppt

文档介绍：Course 8 Contours
Course 8 Contours
Def: edge list
---- ordered set of edge point or fragments.
Def: contour
---- an edge list or expression that is used to represent the curve.
A contour can be open or closed.
Digital Curve.
(1) Curve length:
(2) K-slope: the (angle) direction vector between points with k edge points apart.
(3) K-curvature: the difference between left k-slope and right k-slope at a digital curve point:
2. Curve Representations
1) Chain code
Chain code quantities a space to 8 directions and encodes a contour at each edge point with the directions in an ordered sequence.
------- Chain code pact description.
------- Chain code cannot express branched curves.
plot:
For a digital curve, compute curve length and
slope from a beginning edge point. Then plot the
obtained curve length and slop in space.
------ Line segment in curve; horizontal line in plot.
------ Circular arc in curve; line segment of some direction in space.
------ Using plot can easily segment a curve at discontinuous point of plot.
Graph representation:
Establish topology relations among edge list points.
Each edge point is a graph node.
Struct Node {
int node_number;
int curve_number;
int x, y; // position
char type;
int link[8]; //link relation
int link_direction[8]; //heading or ending
char flag; //process flag
} node;
------ Digital description of curve.
------ Can handle branched curves.
------ Easy in operation.
------ Use more memories, but it can be simplified.
. to remove nodes that have type=2.
Struct link {
int curve_number;
int link_length;
int node_list[];
char flag; //process flag
} link;
3. Polyline representation
Represent an edge list by a set of joined line segments. The edge data not being the joint point will be neglected.