QT实现傅里叶变换动画
时间: 2023-08-03 16:07:18 浏览: 114
要实现傅里叶变换动画,需要使用以下步骤:
1. 生成需要进行傅里叶变换的信号:可以使用任何一段周期性的信号,比如正弦波、方波等。
2. 对信号进行傅里叶变换:可以使用C++中的FFTW库进行傅里叶变换,也可以手动实现傅里叶变换算法。
3. 将变换结果进行可视化:可以使用QT中的QGraphicsView类或者OpenGL进行可视化。将变换结果以动画的形式展示出来。
以下是一个简单的基于QT的傅里叶变换动画示例代码:
```cpp
#include <QApplication>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QPainter>
#include <QTimer>
#include <complex>
#include <vector>
#include <fftw3.h>
const int kWidth = 800;
const int kHeight = 500;
const int kSampleRate = 800; // 采样率
const int kDuration = 5; // 信号持续时间
class SignalGenerator {
public:
explicit SignalGenerator(int sample_rate) : sample_rate_(sample_rate) {}
std::vector<double> GenerateSignal(double frequency) {
std::vector<double> signal(sample_rate_ * kDuration);
for (int i = 0; i < signal.size(); ++i) {
signal[i] = sin(2 * M_PI * i * frequency / sample_rate_);
}
return signal;
}
private:
int sample_rate_;
};
class FourierTransformer {
public:
FourierTransformer(int sample_rate) : sample_rate_(sample_rate) {}
std::vector<std::complex<double>> Transform(const std::vector<double>& signal) {
fftw_complex* in = reinterpret_cast<fftw_complex*>(fftw_malloc(sizeof(fftw_complex) * signal.size()));
fftw_complex* out = reinterpret_cast<fftw_complex*>(fftw_malloc(sizeof(fftw_complex) * signal.size()));
fftw_plan plan = fftw_plan_dft_r2c_1d(signal.size(), const_cast<double*>(signal.data()), out, FFTW_ESTIMATE);
for (int i = 0; i < signal.size(); ++i) {
in[i][0] = signal[i];
in[i][1] = 0;
}
fftw_execute(plan);
std::vector<std::complex<double>> result(signal.size() / 2 + 1);
for (int i = 0; i < result.size(); ++i) {
result[i].real(out[i][0]);
result[i].imag(out[i][1]);
}
fftw_destroy_plan(plan);
fftw_free(in);
fftw_free(out);
return result;
}
private:
int sample_rate_;
};
class FourierAnimation : public QGraphicsView {
public:
FourierAnimation(QWidget* parent = nullptr) : QGraphicsView(parent) {
setFixedSize(kWidth, kHeight);
setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
setRenderHint(QPainter::Antialiasing);
SignalGenerator generator(kSampleRate);
signal_ = generator.GenerateSignal(100);
FourierTransformer transformer(kSampleRate);
spectrum_ = transformer.Transform(signal_);
scene_ = new QGraphicsScene(this);
setScene(scene_);
timer_ = new QTimer(this);
connect(timer_, &QTimer::timeout, this, &FourierAnimation::OnTimeout);
timer_->start(20);
}
void DrawSignal() {
QPainterPath path;
path.moveTo(0, kHeight / 2);
for (int i = 0; i < signal_.size(); ++i) {
double x = i * kWidth / static_cast<double>(signal_.size());
double y = signal_[i] * kHeight / 2 + kHeight / 2;
path.lineTo(x, y);
}
scene_->addPath(path, QPen(Qt::blue));
}
void DrawSpectrum() {
QPainterPath path;
path.moveTo(0, kHeight / 2);
double scale = kHeight / 2 / abs(spectrum_[1]);
for (int i = 1; i < spectrum_.size(); ++i) {
double x = i * kWidth / static_cast<double>(spectrum_.size());
double y = abs(spectrum_[i]) * scale;
path.lineTo(x, kHeight / 2 - y);
}
scene_->addPath(path, QPen(Qt::red));
}
protected:
void resizeEvent(QResizeEvent* event) override {
fitInView(scene_->sceneRect(), Qt::KeepAspectRatio);
QGraphicsView::resizeEvent(event);
}
private:
void OnTimeout() {
scene_->clear();
DrawSignal();
DrawSpectrum();
// 重构信号
std::vector<std::complex<double>> new_spectrum(spectrum_.size());
new_spectrum[1] = spectrum_[1];
for (int i = 2; i < spectrum_.size(); ++i) {
new_spectrum[i] = spectrum_[i] * exp(std::complex<double>(0, 2 * M_PI * i / static_cast<double>(spectrum_.size())));
}
FourierTransformer transformer(kSampleRate);
std::vector<double> new_signal(signal_.size());
std::vector<std::complex<double>> new_spectrum_full(spectrum_.size());
new_spectrum_full[0] = spectrum_[0];
for (int i = 1; i < new_spectrum.size(); ++i) {
new_spectrum_full[i] = new_spectrum[i];
new_spectrum_full[spectrum_.size() - i] = std::conj(new_spectrum[i]);
}
new_signal = transformer.TransformBack(new_spectrum_full);
signal_ = new_signal;
spectrum_ = new_spectrum_full;
}
private:
std::vector<double> signal_;
std::vector<std::complex<double>> spectrum_;
QGraphicsScene* scene_;
QTimer* timer_;
};
int main(int argc, char *argv[]) {
QApplication app(argc, argv);
FourierAnimation animation;
animation.show();
return app.exec();
}
```
这个示例代码中,我们首先使用SignalGenerator类生成一个频率为100Hz的正弦波信号,然后使用FourierTransformer类对信号进行傅里叶变换。变换结果是一个复数向量,表示信号在频域上的幅度和相位信息。
然后我们使用QGraphicsView类创建一个动画窗口,然后在OnTimeout函数中,我们将信号和频谱可视化出来,并重构信号。重构信号的过程是将变换结果通过逆变换转换回时域信号,然后再将其中的高频成分去掉,最后再进行傅里叶变换。这个过程就是傅里叶变换动画的核心了。
最后,我们使用QApplication类创建一个QT应用程序,并显示我们的动画窗口。
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