.. _old_animation-animation_blit_gtk2:

old_animation example code: animation_blit_gtk2.py
==================================================

[`source code <animation_blit_gtk2.py>`_]

::

    #!/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()
    

Keywords: python, matplotlib, pylab, example, codex (see :ref:`how-to-search-examples`)