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Fixed a bug with last two control points calculation
Fixed a bug with last two control points calculation
Marek Rosa - - Load All Authors

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r429:cbe57d7d97d6
r429:cbe57d7d97d6
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qsplineseries.cpp
110 lines | 3.7 KiB | text/x-c | CppLexer
/ src / splinechart / qsplineseries.cpp
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 r295 #include "qsplineseries.h"
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 r401 QTCOMMERCIALCHART_BEGIN_NAMESPACE
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 r295 QSplineSeries::QSplineSeries(QObject *parent) :
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 r419 QLineSeries(parent)
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 r295 {
}
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 r305
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 r419 //QSplineSeries& QSplineSeries::operator << (const QPointF &value)
//{
//// d->m_data.append(value);
// m_data.append(value);
//// emit changed();
// return *this;
//}
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 r318
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 r419 //void QSplineSeries::addData(QPointF value)
//{
// m_data.append(value);
//}
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 r401
void QSplineSeries::calculateControlPoints()
{
// Based on http://www.codeproject.com/Articles/31859/Draw-a-Smooth-Curve-through-a-Set-of-2D-Points-wit
// CPOL Licence
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 r419 int n = m_x.size() - 1;
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 r401 if (n == 1)
{ // Special case: Bezier curve should be a straight line.
// firstControlPoints = new Point[1];
// 3P1 = 2P0 + P3
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 r419 m_controlPoints.append(QPointF((2 * m_x[0] + m_x[1]) / 3, (2 * m_y[0] + m_y[1]) / 3));
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 r401
// P2 = 2P1 P0
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 r419 m_controlPoints.append(QPointF(2 * m_controlPoints[0].x() - m_x[0], 2 * m_controlPoints[0].y() - m_y[0]));
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 r401 return;
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 r318 }
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 r401 // Calculate first Bezier control points
// Right hand side vector
// Set of equations for P0 to Pn points.
//
// | 2 1 0 0 ... 0 0 0 ... 0 0 0 | | P1_1 | | P0 + 2 * P1 |
// | 1 4 1 0 ... 0 0 0 ... 0 0 0 | | P1_2 | | 4 * P1 + 2 * P2 |
// | 0 1 4 1 ... 0 0 0 ... 0 0 0 | | P1_3 | | 4 * P2 + 2 * P3 |
// | . . . . . . . . . . . . | | ... | | ... |
// | 0 0 0 0 ... 1 4 1 ... 0 0 0 | * | P1_i | = | 4 * P(i-1) + 2 * Pi |
// | . . . . . . . . . . . . | | ... | | ... |
// | 0 0 0 0 0 0 0 0 ... 1 4 1 | | P1_(n-1)| | 4 * P(n-2) + 2 * P(n-1) |
// | 0 0 0 0 0 0 0 0 ... 0 2 7 | | P1_n | | 8 * P(n-1) + Pn |
//
QList<qreal> rhs;
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 r419 rhs.append(m_x[0] + 2 * m_x[1]);
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// Set right hand side X values
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 r429 for (int i = 1; i < n - 1; ++i)
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 r419 rhs.append(4 * m_x[i] + 2 * m_x[i + 1]);
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 r401
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 r419 rhs.append((8 * m_x[n - 1] + m_x[n]) / 2.0);
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 r401 // Get first control points X-values
QList<qreal> x = getFirstControlPoints(rhs);
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 r419 rhs[0] = m_y[0] + 2 * m_y[1];
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 r401
// Set right hand side Y values
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 r429 for (int i = 1; i < n - 1; ++i)
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 r419 rhs[i] = 4 * m_y[i] + 2 * m_y[i + 1];
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 r401
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 r419 rhs[n - 1] = (8 * m_y[n - 1] + m_y[n]) / 2.0;
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 r401 // Get first control points Y-values
QList<qreal> y = getFirstControlPoints(rhs);
// Fill output arrays.
// firstControlPoints = new Point[n];
// secondControlPoints = new Point[n];
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 r429 for (int i = 0; i < n; ++i)
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 r318 {
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 r401 // First control point
m_controlPoints.append(QPointF(x[i], y[i]));
// Second control point
if (i < n - 1)
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 r419 m_controlPoints.append(QPointF(2 * m_x[i + 1] - x[i + 1], 2 * m_y[i + 1] - y[i + 1]));
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 r401 else
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 r419 m_controlPoints.append(QPointF((m_x[n] + x[n - 1]) / 2, (m_y[n] + y[n - 1]) / 2));
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 r318 }
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QList<qreal> QSplineSeries::getFirstControlPoints(QList<qreal> rhs)
{
QList<qreal> x; // Solution vector.
QList<qreal> tmp; // Temp workspace.
qreal b = 2.0;
x.append(rhs[0] / b);
tmp.append(0);
for (int i = 1; i < rhs.size(); i++) // Decomposition and forward substitution.
{
tmp.append(1 / b);
b = (i < rhs.size() - 1 ? 4.0 : 3.5) - tmp[i];
x.append((rhs[i] - x[i - 1]) / b);
}
for (int i = 1; i < rhs.size(); i++)
x[rhs.size() - i - 1] -= tmp[rhs.size() - i] * x[rhs.size() - i]; // Backsubstitution.
return x;
}
#include "moc_qsplineseries.cpp"
QTCOMMERCIALCHART_END_NAMESPACE