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#!/usr/bin/env python
"""
This example utlizes restore_region with optional bbox and xy
arguments. The plot is continuously shifted to the left. Instead of
drawing everything again, the plot is saved (copy_from_bbox) and
restored with offset by the amount of the shift. And only newly
exposed area is drawn. This technique may reduce drawing time for some cases.
"""
import time
import gtk, gobject
import matplotlib
matplotlib.use('GTKAgg')
import numpy as np
import matplotlib.pyplot as plt
class UpdateLine(object):
def get_bg_bbox(self):
return self.ax.bbox.padded(-3)
def __init__(self, canvas, ax):
self.cnt = 0
self.canvas = canvas
self.ax = ax
self.prev_time = time.time()
self.start_time = self.prev_time
self.prev_pixel_offset = 0.
self.x0 = 0
self.phases = np.random.random_sample((20,)) * np.pi * 2
self.line, = ax.plot([], [], "-", animated=True, lw=2)
self.point, = ax.plot([], [], "ro", animated=True, lw=2)
self.ax.set_ylim(-1.1, 1.1)
self.background1 = None
cmap = plt.cm.jet
from itertools import cycle
self.color_cycle = cycle(cmap(np.arange(cmap.N)))
def save_bg(self):
self.background1 = self.canvas.copy_from_bbox(self.ax.get_figure().bbox)
self.background2 = self.canvas.copy_from_bbox(self.get_bg_bbox())
def get_dx_data(self, dx_pixel):
tp = self.ax.transData.inverted().transform_point
x0, y0 = tp((0, 0))
x1, y1 = tp((dx_pixel, 0))
return (x1-x0)
def restore_background_shifted(self, dx_pixel):
"""
restore bacground shifted by dx in data coordinate. This only
works if the data coordinate system is linear.
"""
# restore the clean slate background
self.canvas.restore_region(self.background1)
# restore subregion (x1+dx, y1, x2, y2) of the second bg
# in a offset position (x1-dx, y1)
x1, y1, x2, y2 = self.background2.get_extents()
self.canvas.restore_region(self.background2,
bbox=(x1+dx_pixel, y1, x2, y2),
xy=(x1-dx_pixel, y1))
return dx_pixel
def on_draw(self, *args):
self.save_bg()
return False
def update_line(self, *args):
if self.background1 is None:
return True
cur_time = time.time()
pixel_offset = int((cur_time - self.start_time)*100.)
dx_pixel = pixel_offset - self.prev_pixel_offset
self.prev_pixel_offset = pixel_offset
dx_data = self.get_dx_data(dx_pixel) #cur_time - self.prev_time)
x0 = self.x0
self.x0 += dx_data
self.prev_time = cur_time
self.ax.set_xlim(self.x0-2, self.x0+0.1)
# restore background which will plot lines from previous plots
self.restore_background_shifted(dx_pixel) #x0, self.x0)
# This restores lines between [x0-2, x0]
self.line.set_color(self.color_cycle.next())
# now plot line segment within [x0, x0+dx_data],
# Note that we're only plotting a line between [x0, x0+dx_data].
xx = np.array([x0, self.x0])
self.line.set_xdata(xx)
# the for loop below could be improved by using collection.
[(self.line.set_ydata(np.sin(xx+p)),
self.ax.draw_artist(self.line)) \
for p in self.phases]
self.background2 = canvas.copy_from_bbox(self.get_bg_bbox())
self.point.set_xdata([self.x0])
[(self.point.set_ydata(np.sin([self.x0+p])),
self.ax.draw_artist(self.point)) \
for p in self.phases]
self.ax.draw_artist(self.ax.xaxis)
self.ax.draw_artist(self.ax.yaxis)
self.canvas.blit(self.ax.get_figure().bbox)
dt = (time.time()-tstart)
if dt>15:
# print the timing info and quit
print 'FPS:' , self.cnt/dt
gtk.main_quit()
raise SystemExit
self.cnt += 1
return True
plt.rcParams["text.usetex"] = False
fig = plt.figure()
ax = fig.add_subplot(111)
ax.xaxis.set_animated(True)
ax.yaxis.set_animated(True)
canvas = fig.canvas
fig.subplots_adjust(left=0.2, bottom=0.2)
canvas.draw()
# for profiling
tstart = time.time()
ul = UpdateLine(canvas, ax)
gobject.idle_add(ul.update_line)
canvas.mpl_connect('draw_event', ul.on_draw)
plt.show()
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