121 lines
3.7 KiB
C++
121 lines
3.7 KiB
C++
#include "smoothcurve.h"
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#include "qdebug.h"
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QPainterPath SmoothCurve::createSmoothCurve(const QVector<QPointF> &points)
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{
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QPainterPath path;
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int len = points.count();
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if (len < 2) {
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return path;
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}
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QVector<QPointF> firstControlPoints;
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QVector<QPointF> secondControlPoints;
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calculateControlPoints(points, &firstControlPoints, &secondControlPoints);
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path.moveTo(points[0].x(), points[0].y());
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for (int i = 0; i < len - 1; ++i) {
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path.cubicTo(firstControlPoints[i], secondControlPoints[i], points[i + 1]);
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}
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return path;
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}
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QPainterPath SmoothCurve::createSmoothCurve2(const QVector<QPointF> &points)
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{
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//采用Qt原生方法不做任何处理
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int count = points.count();
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if (count == 0) {
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return QPainterPath();
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}
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QPainterPath path(points.at(0));
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for (int i = 0; i < count - 1; ++i) {
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//控制点的 x 坐标为 sp 与 ep 的 x 坐标和的一半
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//第一个控制点 c1 的 y 坐标为起始点 sp 的 y 坐标
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//第二个控制点 c2 的 y 坐标为结束点 ep 的 y 坐标
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QPointF sp = points.at(i);
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QPointF ep = points.at(i + 1);
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QPointF c1 = QPointF((sp.x() + ep.x()) / 2, sp.y());
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QPointF c2 = QPointF((sp.x() + ep.x()) / 2, ep.y());
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path.cubicTo(c1, c2, ep);
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}
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return path;
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}
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void SmoothCurve::calculateFirstControlPoints(double *&result, const double *rhs, int n)
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{
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result = new double[n];
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double *tmp = new double[n];
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double b = 2.0;
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result[0] = rhs[0] / b;
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for (int i = 1; i < n; ++i) {
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tmp[i] = 1 / b;
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b = (i < n - 1 ? 4.0 : 3.5) - tmp[i];
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result[i] = (rhs[i] - result[i - 1]) / b;
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}
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for (int i = 1; i < n; ++i) {
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result[n - i - 1] -= tmp[n - i] * result[n - i];
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}
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delete tmp;
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}
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void SmoothCurve::calculateControlPoints(const QVector<QPointF> &datas,
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QVector<QPointF> *firstControlPoints,
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QVector<QPointF> *secondControlPoints)
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{
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int n = datas.count() - 1;
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for (int i = 0; i < n; ++i) {
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firstControlPoints->append(QPointF());
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secondControlPoints->append(QPointF());
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}
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if (n == 1) {
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(*firstControlPoints)[0].rx() = (2 * datas[0].x() + datas[1].x()) / 3;
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(*firstControlPoints)[0].ry() = (2 * datas[0].y() + datas[1].y()) / 3;
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(*secondControlPoints)[0].rx() = 2 * (*firstControlPoints)[0].x() - datas[0].x();
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(*secondControlPoints)[0].ry() = 2 * (*firstControlPoints)[0].y() - datas[0].y();
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return;
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}
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double *xs = 0;
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double *ys = 0;
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double *rhsx = new double[n];
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double *rhsy = new double[n];
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for (int i = 1; i < n - 1; ++i) {
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rhsx[i] = 4 * datas[i].x() + 2 * datas[i + 1].x();
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rhsy[i] = 4 * datas[i].y() + 2 * datas[i + 1].y();
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}
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rhsx[0] = datas[0].x() + 2 * datas[1].x();
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rhsx[n - 1] = (8 * datas[n - 1].x() + datas[n].x()) / 2.0;
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rhsy[0] = datas[0].y() + 2 * datas[1].y();
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rhsy[n - 1] = (8 * datas[n - 1].y() + datas[n].y()) / 2.0;
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calculateFirstControlPoints(xs, rhsx, n);
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calculateFirstControlPoints(ys, rhsy, n);
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for (int i = 0; i < n; ++i) {
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(*firstControlPoints)[i].rx() = xs[i];
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(*firstControlPoints)[i].ry() = ys[i];
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if (i < n - 1) {
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(*secondControlPoints)[i].rx() = 2 * datas[i + 1].x() - xs[i + 1];
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(*secondControlPoints)[i].ry() = 2 * datas[i + 1].y() - ys[i + 1];
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} else {
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(*secondControlPoints)[i].rx() = (datas[n].x() + xs[n - 1]) / 2;
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(*secondControlPoints)[i].ry() = (datas[n].y() + ys[n - 1]) / 2;
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}
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}
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delete xs;
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delete ys;
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delete rhsx;
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delete rhsy;
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}
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