pyqtgraph/chaco/guiqwt:快速滚动时间跟踪演示

Question

我想在python中实现一个快速滚动的时间跟踪工具。在numpy数组中，时间跟踪数据已经全部在内存中，并且很大(>1e6个样本)。我需要一种快速目视检查的工具。

我已经尝试使用Matplotlib+PySide，但更新速度不够快。

能否在另一个工具包(如pygraphqt/chaco/quiqwt)中重现Matplotlib+Pyside演示?我一个都不认识，我愿意学习在这个应用程序中表现更好的一个。

为了在我的工作流程中有用，所选择的框架应该允许从交互式python会话中运行绘图，并且应该是快速和可扩展的(最终我将需要在同一窗口上同步滚动几个绘图)。原则上，pyqtgraph、guqwt或chaco似乎都是不错的选择。但让我们用一个真实的例子来判断。

谢谢。

Answer 1

这是pyqtgraph的版本。我尽量保持代码与原始演示相似。在我的系统上，pyqtgraph的运行速度只比matplotlib快5倍左右，当所有数据都可见时，它仍然很慢(约1fps)。matplotlib和pyqtgraph之间的主要性能差异在于吞吐量——绘制新数据的速度。

为了获得更好的性能，我建议使用一些基于gpu的绘图库，如visvis或gallery。Pyqtgraph将在未来添加GPU支持，但目前还没有。也有一些努力将matplotlib引入GPU，但我还没有看到任何结果。

## adapted from http://stackoverflow.com/questions/16824718/python-matplotlib-pyside-fast-timetrace-scrolling
from PySide import QtGui, QtCore
import numpy as np
import pyqtgraph as pg
N_SAMPLES = 1e6
def test_plot():
    time = np.arange(N_SAMPLES)*1e-3
    sample = np.random.randn(N_SAMPLES)
    plt = pg.PlotWidget(title="Use the slider to scroll and the spin-box to set the width")
    plt.addLegend()
    plt.plot(time, sample, name="Gaussian noise")
    q = ScrollingToolQT(plt)
    return q   # WARNING: it's important to return this object otherwise
            # python will delete the reference and the GUI will not respond!

class ScrollingToolQT(object):
    def __init__(self, fig):
        # Setup data range variables for scrolling
        self.fig = fig
        self.xmin, self.xmax = fig.plotItem.vb.childrenBounds()[0]
        self.step = 1 # axis units
        self.scale = 1e3 # conversion betweeen scrolling units and axis units
        # Retrive the QMainWindow used by current figure and add a toolbar
        # to host the new widgets
        self.win = QtGui.QMainWindow()
        self.win.show()
        self.win.resize(800,600)
        self.win.setCentralWidget(fig)
        self.toolbar = QtGui.QToolBar()
        self.win.addToolBar(QtCore.Qt.BottomToolBarArea, self.toolbar)
        # Create the slider and spinbox for x-axis scrolling in toolbar
        self.set_slider(self.toolbar)
        self.set_spinbox(self.toolbar)
        # Set the initial xlimits coherently with values in slider and spinbox
        self.set_xlim = self.fig.setXRange
        self.set_xlim(0, self.step)
    def set_slider(self, parent):
        # Slider only support integer ranges so use ms as base unit
        smin, smax = self.xmin*self.scale, self.xmax*self.scale
        self.slider = QtGui.QSlider(QtCore.Qt.Horizontal, parent=parent)
        self.slider.setTickPosition(QtGui.QSlider.TicksAbove)
        self.slider.setTickInterval((smax-smin)/10.)
        self.slider.setMinimum(smin)
        self.slider.setMaximum(smax-self.step*self.scale)
        self.slider.setSingleStep(self.step*self.scale/5.)
        self.slider.setPageStep(self.step*self.scale)
        self.slider.setValue(0)  # set the initial position
        self.slider.valueChanged.connect(self.xpos_changed)
        parent.addWidget(self.slider)
    def set_spinbox(self, parent):
        self.spinb = QtGui.QDoubleSpinBox(parent=parent)
        self.spinb.setDecimals(3)
        self.spinb.setRange(0.001, 3600.)
        self.spinb.setSuffix(" s")
        self.spinb.setValue(self.step)   # set the initial width
        self.spinb.valueChanged.connect(self.xwidth_changed)
        parent.addWidget(self.spinb)
    def xpos_changed(self, pos):
        #pprint("Position (in scroll units) %fn" %pos)
        #        self.pos = pos/self.scale
        pos /= self.scale
        self.set_xlim(pos, pos + self.step, padding=0)
    def xwidth_changed(self, xwidth):
        #pprint("Width (axis units) %fn" % step)
        if xwidth <= 0: return
        self.step = xwidth
        self.slider.setSingleStep(self.step*self.scale/5.)
        self.slider.setPageStep(self.step*self.scale)
        old_xlim = self.fig.plotItem.vb.viewRange()[0]
        self.xpos_changed(old_xlim[0] * self.scale)
if __name__ == "__main__":
    app = pg.mkQApp()
    q = test_plot()
    app.exec_()