Ah,
I did not know that. I shall investigate.

Thanks,
Gerald.

On 6/05/2011 7:27 AM, Benjamin Root wrote:


On Tue, May 3, 2011 at 3:57 AM, Gerald Storer <gds@mrxtech.com.au> wrote:
Hello,

I've been trying to animate some plots with the qt backend and run into
a couple of problems.

Firstly,
I'd like to be able to update the axis limits in an automated fashion as
the data changes size.

Secondly,
Resizing figures appears to redraw everything _but_ items with the
animation flag.  The is causing me problems when the animation is paused
or the frames are occurring slow enough such that there is a noticable
period where the my lines disappear.

I've sort of solved both of these problems but the solutions seem
hackish.  In particular updating the axis limits is slowing the
animation by 25% and toggling the animated field using the qt events
just feels like its asking for trouble.

Below is the qt animation example with my solutions.  Adjust the size of
the plot after the animation finishes to see the effect of the resize
hack.  I would be grateful if anyone could suggest some improvements.

Thanks,
Gerald.

# For detailed comments on animation and the techniqes used here, see

# the wiki entry http://www.scipy.org/Cookbook/Matplotlib/Animations

import os

import sys

#import matplotlib

#matplotlib.use('Qt4Agg')

from matplotlib.figure import Figure

from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas

from PyQt4 import QtCore, QtGui

ITERS = 100

import numpy as np

import time

class BlitQT(FigureCanvas):

    def __init__(self):

        FigureCanvas.__init__(self, Figure())

        self.ax = self.figure.add_subplot(111)

        #self.ax.grid()

        self.draw()

        self.old_size = self.ax.bbox.width, self.ax.bbox.height

        self.ax_background = self.copy_from_bbox(self.ax.bbox)

        self.cnt = 0

        self.x = np.arange(0,2*np.pi,0.01)

        self.sin_line, = self.ax.plot(self.x, np.sin(self.x), animated=True)

        self.cos_line, = self.ax.plot(self.x, np.cos(self.x), animated=True)

        self.draw()

        self.old_limits = self.ax.get_xlim(),self.ax.get_ylim()

        self.tstart = time.time()

        self.maintimer = self.startTimer(10)

    ## HACK for disapearing objects on resize

    def resizeEvent(self,evt):

        super(BlitQT,self).resizeEvent(evt)

        self.sin_line.set_animated(False)

    def paintEvent(self,evt):

        super(BlitQT,self).paintEvent(evt)

        self.sin_line.set_animated(True)

    def timerEvent(self, evt):

        current_size = self.ax.bbox.width, self.ax.bbox.height

        if self.old_size != current_size:

            self.old_size = current_size

            #self.ax.clear()

            #self.ax.grid()

            self.draw()

            self.ax_background = self.copy_from_bbox(self.ax.bbox)

        self.restore_region(self.ax_background)

        # update the data

        self.sin_line.set_ydata(np.sin(self.x+self.cnt/10.0)*self.cnt/100.0)

        self.cos_line.set_ydata(np.cos(self.x+self.cnt/10.0)*self.cnt/100.0)

        ## HACK for updating axis limits

        self.ax.relim()

        self.ax.autoscale_view()

        current_limits = self.ax.get_xlim(),self.ax.get_ylim()

        if self.old_limits != current_limits:

            self.old_limits = current_limits

            self.draw()

            self.ax_background = self.copy_from_bbox(self.ax.bbox)

            self.blit(self.figure.bbox)



        # just draw the animated artist

        self.ax.draw_artist(self.sin_line)

        self.ax.draw_artist(self.cos_line)

        # just redraw the axes rectangle

        self.blit(self.ax.bbox)

        if self.cnt == 0:

            # TODO: this shouldn't be necessary, but if it is excluded the

            # canvas outside the axes is not initially painted.

            self.draw()

        if self.cnt==ITERS:

            # print the timing info and quit

            print 'FPS:' , ITERS/(time.time()-self.tstart)

            #sys.exit()

            self.killTimer(self.maintimer)

        else:

            self.cnt += 1

app = QtGui.QApplication(sys.argv)

widget = BlitQT()

widget.show()

sys.exit(app.exec_())


Gerald,

I haven't looked at your code, but I would like to point out that if you wish to experiment a little further with animations in matplotlib, there is a animation module that is in the  current development branch (but has not been officially released).  Maybe using it might help make your code less "hack-ish"?  We would also greatly welcome any and all comments on the module before the next release of matplotlib.

Ben Root


--
Gerald Storer | MRX Technologies
+61 8 9227 4529 | gds@mrxtech.com.au | http://www.mrxtech.com.au