approx_chain

Herror ::approx_chain_simple ( const HTuple &Row, const HTuple &Column, HTuple *ArcCenterRow, HTuple *ArcCenterCol, HTuple *ArcAngle, HTuple *ArcBeginRow, HTuple *ArcBeginCol, HTuple *LineBeginRow, HTuple *LineBeginCol, HTuple *LineEndRow, HTuple *LineEndCol, HTuple *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 `->` HTuple.long
Row of the contour.
Default value: 32

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

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

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

`ArcAngle` (output_control)	arc.angle.rad-array `->` HTuple.double *
Angle of an arc.

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

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

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

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

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

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

`Order` (output_control)	integer-array `->` HTuple.long *
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 H_MSG_TRUE if the parameters are correct. Otherwise an exception is raised.

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