using matplotlib to plot data vs unix time with yaxis_date is ungoogleable

plot_image_vs_time.py

#!/usr/bin/env python3

import sys
import os

def plot_image_vs_time(data, timestamps, x0, dx, xlabel, title=None):
    import datetime

    try:
        import numpy
        import matplotlib
    except:
        print('warning: plotting skipped, please "pip3 install matplotlib" or the equivalent on your OS')
        exit()

    matplotlib.use('pdf')
    import matplotlib.pyplot

    T, X = data.shape
    if T < 2: raise RuntimeError('need multiple rows of pixels to plot')
    if len(timestamps) != T: raise RuntimeError('need one timestamp per row of pixels')
    dt_mean = (timestamps[T - 1] - timestamps[0]) / (T - 1)

    fig, ax = matplotlib.pyplot.subplots()

    # assumes that timestamps[0] and x0 specify the CENTRE of the oldest leftmost pixel
    extent = [x0 - 0.5 * dx, x0 + (X - 0.5) * dx,
              matplotlib.dates.date2num(datetime.datetime.utcfromtimestamp(timestamps[T - 1] + 0.5 * dt_mean)),
              matplotlib.dates.date2num(datetime.datetime.utcfromtimestamp(timestamps[0] - 0.5 * dt_mean)) ]

    # aspect is calculated from extent to force square pixels on screen
    pos = ax.imshow(data, extent=extent, aspect=abs(extent[1] - extent[0]) * data.shape[0] / (abs(extent[3] - extent[2]) * data.shape[1]), vmin=0, vmax=255)

    ax.yaxis_date()
    ax.set(xlabel=xlabel)
    if title:
        ax.set(title=title)
        ax.title.set_size(10)

    if (sys.stdout.isatty()):
        fig.savefig('/tmp/out.pdf', bbox_inches='tight')
        os.system('open /tmp/out.pdf 2>/dev/null')
    else: fig.savefig(sys.stdout.buffer, bbox_inches='tight')