approx_chain

approx_chain_simple ( : : Row, Column : ArcCenterRow, ArcCenterCol, ArcAngle, ArcBeginRow, ArcBeginCol, LineBeginRow, LineBeginCol, LineEndRow, LineEndCol, Order )

Approximate a contour by arcs and lines.

The contour of a curve is approximated by a sequence of lines and arcs.

The result of the procedure is returned separately as arcs and lines. If one is interested in the sequence of the segments the individual resulting elements can be read successively from the resulting tuples. The sequence can be taken from the return parameter order (0: next element is next line segment, 1: next element is next arc segment).

The operator approx_chain_simple behaves similarly as approx_chain except that in the case of approx_chain_simple the missing parameters are internally allocated as follows: MinWidthCoord = 1.0, MaxWidthCoord = 3.0, ThreshStart = 0.5, ThreshEnd = 0.9, ThreshStep = 0.3, MinWidthSmooth = 1.0, MaxWidthSmooth = 3.0, MinWidthCurve = 2, MaxWidthCurve = 9, Weight1 = 1.0, Weight2 = 1.0, Weight3 = 1.0.

Parameters

`Row` (input_control)	point.y `->` integer
Row of the contour.
Default value: 32

`Column` (input_control)	point.x `->` integer
Column of the contour.
Default value: 32

`ArcCenterRow` (output_control)	arc.center.y-array `->` integer
Row of the center of an arc.

`ArcCenterCol` (output_control)	arc.center.x-array `->` integer
Column of the center of an arc.

`ArcAngle` (output_control)	arc.angle.rad-array `->` real
Angle of an arc.

`ArcBeginRow` (output_control)	arc.begin.y-array `->` integer
Row of the starting point of an arc.

`ArcBeginCol` (output_control)	arc.begin.x-array `->` integer
Column of the starting point of an arc.

`LineBeginRow` (output_control)	line.begin.y-array `->` integer
Row of the starting point of a line segment.

`LineBeginCol` (output_control)	line.begin.x-array `->` integer
Column of the starting point of a line segment.

`LineEndRow` (output_control)	line.end.y-array `->` integer
Row of the ending point of a line segment.

`LineEndCol` (output_control)	line.end.x-array `->` integer
Column of the ending point of a line segment.

`Order` (output_control)	integer-array `->` integer
Sequence of line (value 0) and arc segments (value 1).

Example

/* read edge image */
read_image(&Image,"fig1_kan");
/* construct edge region */
hysteresis_threshold(Image,&RK1,64,255,40,1);
connection(RK1,&Rand);
/* fetch chain code */
T_get_region_contour(Rand,&Rows,&Columns);
firstline = get_i(Tline,0);
firstcol = get_i(Tcol,0);
/* approximation with lines and circular arcs */
T_approx_chain_simple(Rows,Columns,
                &Bzl,&Bzc,&Br,&Bwl,&Bwc,&Ll0,&Lc0,&Ll1,&Lc1,&order);
nob = length_tuple(Bzl);
nol = length_tuple(Ll0);
/* draw lines and arcs */
set_i(WindowHandleTuple,WindowHandle,0) ;
set_line_width(WindowHandle,4);
if (nob>0) T_disp_arc(Bzl,Bzc,Br,Bwl,Bwc);
set_line_width(WindowHandle,1);
if (nol>0) T_disp_line(WindowHandleTuple,Ll0,Lc0,Ll1,Lc1);

Result

The operator approx_chain_simple returns the value 2 (H_MSG_TRUE) if the parameters are correct. Otherwise an exception is raised.

Parallelization Information

approx_chain_simple is reentrant and processed without parallelization.

Possible Predecessors

sobel_amp, edges_image, get_region_contour, threshold, hysteresis_threshold

Possible Successors

set_line_width, disp_arc, disp_line

Alternatives

get_region_polygon, approx_chain

Module

Region processing