Sources_For_Linux/Qwt/doc/man/man3/QwtWeedingCurveFitter.3

.TH "QwtWeedingCurveFitter" 3 "Mon Dec 28 2020" "Version 6.1.6" "Qwt User's Guide" \" -*- nroff -*-
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.SH NAME
QwtWeedingCurveFitter \- A curve fitter implementing Douglas and Peucker algorithm\&.  

.SH SYNOPSIS
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.PP
.PP
\fC#include <qwt_curve_fitter\&.h>\fP
.PP
Inherits \fBQwtCurveFitter\fP\&.
.SS "Public Member Functions"

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.ti -1c
.RI "\fBQwtWeedingCurveFitter\fP (double \fBtolerance\fP=1\&.0)"
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.RI "virtual \fB~QwtWeedingCurveFitter\fP ()"
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.RI "Destructor\&. "
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.RI "void \fBsetTolerance\fP (double)"
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.RI "double \fBtolerance\fP () const"
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.RI "void \fBsetChunkSize\fP (uint)"
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.RI "uint \fBchunkSize\fP () const"
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.RI "virtual QPolygonF \fBfitCurve\fP (const QPolygonF &) const"
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.SS "Additional Inherited Members"
.SH "Detailed Description"
.PP 
A curve fitter implementing Douglas and Peucker algorithm\&. 

The purpose of the Douglas and Peucker algorithm is that given a 'curve' composed of line segments to find a curve not too dissimilar but that has fewer points\&. The algorithm defines 'too dissimilar' based on the maximum distance (tolerance) between the original curve and the smoothed curve\&.
.PP
The runtime of the algorithm increases non linear ( worst case O( n*n ) ) and might be very slow for huge polygons\&. To avoid performance issues it might be useful to split the polygon ( \fBsetChunkSize()\fP ) and to run the algorithm for these smaller parts\&. The disadvantage of having no interpolation at the borders is for most use cases irrelevant\&.
.PP
The smoothed curve consists of a subset of the points that defined the original curve\&.
.PP
In opposite to \fBQwtSplineCurveFitter\fP the Douglas and Peucker algorithm reduces the number of points\&. By adjusting the tolerance parameter according to the axis scales \fBQwtSplineCurveFitter\fP can be used to implement different level of details to speed up painting of curves of many points\&. 
.SH "Constructor & Destructor Documentation"
.PP 
.SS "QwtWeedingCurveFitter::QwtWeedingCurveFitter (double tolerance = \fC1\&.0\fP)"
Constructor
.PP
\fBParameters\fP
.RS 4
\fItolerance\fP Tolerance 
.RE
.PP
\fBSee also\fP
.RS 4
\fBsetTolerance()\fP, \fBtolerance()\fP 
.RE
.PP

.SH "Member Function Documentation"
.PP 
.SS "uint QwtWeedingCurveFitter::chunkSize () const"

.PP
\fBReturns\fP
.RS 4
Maximum for the number of points passed to a run of the algorithm - or 0, when unlimited 
.RE
.PP
\fBSee also\fP
.RS 4
\fBsetChunkSize()\fP 
.RE
.PP

.SS "QPolygonF QwtWeedingCurveFitter::fitCurve (const QPolygonF & points) const\fC [virtual]\fP"

.PP
\fBParameters\fP
.RS 4
\fIpoints\fP Series of data points 
.RE
.PP
\fBReturns\fP
.RS 4
Curve points 
.RE
.PP

.PP
Implements \fBQwtCurveFitter\fP\&.
.SS "void QwtWeedingCurveFitter::setChunkSize (uint numPoints)"
Limit the number of points passed to a run of the algorithm
.PP
The runtime of the Douglas Peucker algorithm increases non linear with the number of points\&. For a chunk size > 0 the polygon is split into pieces passed to the algorithm one by one\&.
.PP
\fBParameters\fP
.RS 4
\fInumPoints\fP Maximum for the number of points passed to the algorithm
.RE
.PP
\fBSee also\fP
.RS 4
\fBchunkSize()\fP 
.RE
.PP

.SS "void QwtWeedingCurveFitter::setTolerance (double tolerance)"
Assign the tolerance
.PP
The tolerance is the maximum distance, that is acceptable between the original curve and the smoothed curve\&.
.PP
Increasing the tolerance will reduce the number of the resulting points\&.
.PP
\fBParameters\fP
.RS 4
\fItolerance\fP Tolerance
.RE
.PP
\fBSee also\fP
.RS 4
\fBtolerance()\fP 
.RE
.PP

.SS "double QwtWeedingCurveFitter::tolerance () const"

.PP
\fBReturns\fP
.RS 4
Tolerance 
.RE
.PP
\fBSee also\fP
.RS 4
\fBsetTolerance()\fP 
.RE
.PP


.SH "Author"
.PP 
Generated automatically by Doxygen for Qwt User's Guide from the source code\&.