included low pass filter in package and add to plot_data example

examples/gui/viewer2d/backend.py

@@ -13,7 +13,7 @@ from typing import Literal, Optional, Sequence, Tuple
 import cv2
 import numpy as np
 import orisys
-from scipy.signal import butter, filtfilt
+from orisys.signal_processing import lowpass_filter
 
 FORCE_SAMPLE_RATE_HZ = 30.0
 PLOT_BUFFER_POINTS = 120
@@ -61,32 +61,6 @@ class ForcePlotState:
     y_ranges: Tuple[Tuple[float, float], Tuple[float, float], Tuple[float, float]]
 
 
-def lowpass_filter(
-    data,
-    cutoff_hz: float,
-    sample_rate_hz: float = FORCE_SAMPLE_RATE_HZ,
-    order: int = 2,
-) -> np.ndarray:
-    """Zero-phase Butterworth low-pass for uniformly sampled 1-D data."""
-    y = np.asarray(data, dtype=np.float64)
-    if cutoff_hz == 0:
-        return y.copy()
-    if y.size == 0:
-        return y
-
-    nyquist = 0.5 * sample_rate_hz
-    if cutoff_hz < 0 or cutoff_hz >= nyquist:
-        raise ValueError(
-            f"cutoff_hz must be in (0, {nyquist}) for sample_rate_hz={sample_rate_hz}"
-        )
-
-    b, a = butter(order, cutoff_hz / nyquist, btype="low")
-    padlen = 3 * (max(len(b), len(a)) - 1)
-    if y.size <= padlen:
-        return y.copy()
-    return filtfilt(b, a, y)
-
-
 def ensure_bgr(img: Optional[np.ndarray]) -> Optional[np.ndarray]:
     if img is None:
         return None