# -*- coding: utf-8 -*-
import matplotlib.pyplot as plt
import numpy as np
from ..signal import signal_resample
[docs]
def video_plot(video, sampling_rate=30, frames=3, signals=None):
"""**Visualize video**
This function plots a few frames from a video as an image.
Parameters
----------
video : np.ndarray
An video data numpy array of the shape (frame, channel, height, width)
sampling_rate : int
The number of frames per second (FPS), by default 30.
frames : int or list
What frames to plot. If list, indicates the index of frames. If number, will select
linearly spaced frames.
signals : list
A list of signals to plot under the videos.
Examples
--------
.. ipython:: python
import neurokit2 as nk
# video, sampling_rate = nk.read_video("video.mp4")
# nk.video_plot(video, sampling_rate=sampling_rate)
"""
# Put into list if it's not already
if isinstance(video, list) is False:
video = [video]
# How many subplots
nrows = len(video)
if signals is not None:
if isinstance(signals, list) is False:
signals = [signals]
nrows += len(signals)
# Get x-axis (of the first video)
length = video[0].shape[0]
desired_length = 1000
if length > 1000:
desired_length = length
# TODO: height_ratios doesn't work as expected
_, ax = plt.subplots(
nrows=nrows,
sharex=True,
# gridspec_kw={"height_ratios": height_ratios},
constrained_layout=True,
)
# Get frame locations
if isinstance(frames, int):
frames = np.linspace(0, length - 1, frames).astype(int)
# For each videos in the list, plot them
if nrows == 1:
ax = [ax] # Otherwise it will make ax[i] non subscritable
for i, vid in enumerate(video):
vid = _video_plot_format(vid, frames=frames, desired_length=desired_length)
ax[i].axis("off")
ax[i].imshow(vid, aspect="auto")
if signals is not None:
for j, signal in enumerate(signals):
# Make sure the size is correct
if len(signal) != length:
signal = signal_resample(signal, desired_length=desired_length)
# Plot
ax[i + j + 1].plot(signal)
for frame in frames:
ax[i + j + 1].axvline(
x=int(np.round(frame / length * desired_length)),
color="black",
linestyle="--",
alpha=0.5,
)
# Ticks in seconds
plt.xticks(
np.linspace(0, desired_length, 5),
np.char.mod("%.1f", np.linspace(0, length / sampling_rate, 5)),
)
plt.xlabel("Time (s)")
def _video_plot_format(vid, frames=[0], desired_length=1000):
# Try loading cv2
try:
import cv2
except ImportError:
raise ImportError(
"The 'cv2' module is required for this function to run. ",
"Please install it first (`pip install opencv-python`).",
)
# (frames, height, width, RGB channels) for cv2
vid = vid.swapaxes(3, 1).swapaxes(2, 1)
# Concatenate
excerpt = np.concatenate(vid[frames], axis=1)
# Rescale
excerpt = cv2.resize(
excerpt.astype("uint8"),
dsize=(desired_length, vid.shape[1]),
interpolation=cv2.INTER_CUBIC,
)
return excerpt
