scipy butterworth带通滤波器的Java替代方案

import org.jtransforms.fft.DoubleFFT_1D;

public class ButterworthBandpassFilter {
    private double[] filterCoefficients;
    private int filterLength;

    public ButterworthBandpassFilter(double lowCutoff, double highCutoff, int sampleRate, int filterOrder) {
        this.filterLength = (int) Math.pow(2, Math.ceil(Math.log(sampleRate) / Math.log(2)));
        this.filterCoefficients = new double[filterLength];
        designFilter(lowCutoff, highCutoff, sampleRate, filterOrder);
    }

    private void designFilter(double lowCutoff, double highCutoff, int sampleRate, int filterOrder) {
        // 这里需要实现Butterworth滤波器的设计算法
        // 例如，可以使用双二阶节（biquad）来实现
        // 这只是一个示例，实际实现会更复杂
        for (int i = 0; i < filterLength; i++) {
            double freq = (double) i / filterLength * sampleRate;
            if (freq >= lowCutoff && freq <= highCutoff) {
                filterCoefficients[i] = 1.0;
            } else {
                filterCoefficients[i] = 0.0;
            }
        }
    }

    public double[] applyFilter(double[] input) {
        DoubleFFT_1D fft = new DoubleFFT_1D(filterLength);
        double[] fftInput = new double[filterLength * 2];
        double[] fftOutput = new double[filterLength * 2];

        System.arraycopy(input, 0, fftInput, 0, filterLength);
        fft.realForwardFull(fftInput);

        for (int i = 0; i < fftInput.length; i += 2) {
            double real = fftInput[i];
            double imag = fftInput[i + 1];
            // 应用滤波器系数
            fftInput[i] = real * filterCoefficients[i / 2];
            fftInput[i + 1] = imag * filterCoefficients[i / 2];
        }

        fft.realInverseFull(fftInput, true);
        return fftOutput;
    }

    public static void main(String[] args) {
        ButterworthBandpassFilter filter = new ButterworthBandpassFilter(1000, 2000, 44100, 4);
        double[] input = {/* 输入信号数据 */};
        double[] output = filter.applyFilter(input);
        // 处理输出信号
    }
}