route_animation.py 文件源码

def _animate(fig, ax, frame_data, line_width=2, fps=10, tail_color='r',
             tail_alpha=0.75, head_color='b', head_alpha=1):
  segments, segment_frames, timestamps, fade_frames = frame_data
  head_color = np.array(to_rgb(head_color))[None]
  tail_color = np.array(to_rgb(tail_color))[None]

  # start with all segments transparent
  segment_colors = np.zeros((len(segments), 4), dtype=float)
  lines = LineCollection(segments, linewidths=line_width, colors=segment_colors)
  ax.add_collection(lines)

  timer = ax.text(1, 0, '0:00:00', transform=ax.transAxes, zorder=3,
                  verticalalignment='bottom', horizontalalignment='right',
                  bbox=dict(facecolor='white'))

  def update_frame(frame_idx):
    frame_diff = frame_idx - segment_frames
    mask = frame_diff < 0
    # compute head alpha
    alpha1 = 1 - np.minimum(frame_diff/fade_frames, 1)
    alpha1[mask] = 0
    alpha1 *= head_alpha
    # compute tail alpha
    alpha2 = (1 - mask) * tail_alpha
    # composite alpha and colors
    color, alpha = _blend_alpha(head_color, alpha1, tail_color, alpha2)
    segment_colors[:, :3] = color
    segment_colors[:, 3] = alpha

    lines.set_color(segment_colors)
    timer.set_text(timestamps[frame_idx])
    return lines, timer

  interval = 1000. / fps
  return FuncAnimation(fig, update_frame, frames=len(timestamps), blit=True,
                       interval=interval, repeat=True)