如何加快查科图像的绘制

Question

I am trying to animate a bunch of 2D images with chaco, but unfortunately it does not seem to be as fast as my application needs it. At the moment I am building a chaco Plot and using img_plot , eg:

pd = ArrayPlotData()
pd.set_data("imagedata", myarray)
plot = Plot(pd)
plot.img_plot("imagedata", interpolation="nearest")

And to update the image, I use the following:

pd.set_data("imagedata", my_new_array)

This works, however is not fast enough. Is there any way to speed it up? Any lower-level function that allows a faster update of the image?

Answer 1

This is just a thought, but would adding every image initially into your ArrayPlotData solve your problem? Then you aren't adding a new image at each step in your animation, and just calling img_plot() on the next series. For example, if your images are stored in a numpy array called images[nt, nx, ny]:

pd = ArrayPlotData()
for index in range(images.shape[0]): #Assuming you want to iterate over nt
    pd.set_data('', images[index,:,:], generate_name = True)
plot = Plot(pd)

This automatically names each image 'series1', 'series2', etc. Then you can call:

plot.img_plot('series1', interpolation = 'nearest') #or 'series2' etc. 

for every image in your animation without having to call set_data().

You can get a sorted list of your image names ['series1, 'series2', ...] to iterate over using:

from natsort import natsorted #sort using natural sorting
names = natsorted(pd.list_data())

Would that help with the bottleneck?

Answer 2

Here's an example of how I do animations in Chaco using a timer. Usually the trick (as J Corson said) is to load your data into an array and then just use an index to take successive slices of the array.

from chaco.api import ArrayPlotData, Plot
from enable.api import ComponentEditor
import numpy as np
from pyface.timer.api import Timer
from traits.api import Array, Bool, Event, HasTraits, Instance, Int
from traitsui.api import ButtonEditor, Item, View


class AnimationDemo(HasTraits):
    plot = Instance(Plot)
    x = Array
    y = Array
    run = Bool(False)
    go = Event
    idx = Int

    def _x_default(self):
        x = np.linspace(-np.pi, np.pi, 100)
        return x

    def _y_default(self):
        phi = np.linspace(0, 2 * np.pi, 360)
        y = np.sin(self.x[:, np.newaxis] + phi[np.newaxis, :]) - \
            0.1 * np.sin(13 * self.x[:, np.newaxis] - 7 * phi[np.newaxis, :])
        return y

    def _plot_default(self):
        plot_data = ArrayPlotData(y=self.y[:, 0], x=self.x)
        plot = Plot(plot_data)
        plot.plot(('x', 'y'))
        return plot

    def _go_fired(self):
        if not self.run:
            self.run = True
        else:
            self.run = False

    def _run_changed(self):
        if self.run:
            self.timer.Start()
        else:
            self.timer.Stop()

    def _run_default(self):
        self.timer = Timer(5, self._timer_tick)
        return False

    def _timer_tick(self):
        if not self.run:
            raise StopIteration
        else:
            if self.idx >= 360:
                self.idx = 0
            self.plot.data.set_data('y', self.y[:, self.idx])
            self.idx += 1

    traits_view = View(
        Item('plot', editor=ComponentEditor(), show_label=False),
        Item('go', editor=ButtonEditor(label="Start/Stop"), show_label=False),
    )


if __name__ == "__main__":
    ad = AnimationDemo()
    ad.edit_traits()

I get something like this: