三个子图的Pyqtgraph输出如何显示？

Question

使用PyQtGraph，我想在一个图表中生成三个子图并将该图表导出到一个文件中。

我将重复这一点很多次，它对性能非常敏感。因此，我不需要将图表带到屏幕上。

下面的代码显示了屏幕上的三个子图，但是导出到该文件目前无法正常工作。我有什么要作为参数传递给ImageExporter？ （如果可能的话：无论如何我只需做导出而不将图表带到屏幕上？）

from pyqtgraph.Qt import QtGui, QtCore
import pyqtgraph as pg
import pyqtgraph.exporters
import numpy as np

print("pyqtgraph.__version__:", pyqtgraph.__version__)

app = QtGui.QApplication([])

view = pg.GraphicsView()
l = pg.GraphicsLayout(border=(100, 100, 100))
view.setCentralItem(l)
view.show()
view.resize(800, 600)
# l.addLayout(colspan=1, border=(50, 0, 0))
p1 = l.addPlot()
l.nextRow()
p2 = l.addPlot()
l.nextRow()
p3 = l.addPlot()
p1.hideAxis("left")
p1.hideAxis("bottom")
p2.hideAxis("left")
p2.hideAxis("bottom")
p3.hideAxis("left")
p3.hideAxis("bottom")

p1.plot([1, 3, 2, 4, 3, 5])
p2.plot([1, 3, 2, 4, 3, 5])
p3.plot([1, 3, 2, 4, 3, 5])
# exporter = pg.exporters.ImageExporter(plt.plotItem)
exporter = pg.exporters.ImageExporter(view.currentItem)
# set export parameters if needed
exporter.parameters()['width'] = 100  # (note this also affects height parameter)
# save to file
exporter.export('fileName.png')

结果是：

pyqtgraph.__version__: 0.11.0.dev0+g9aaae8d
....
  File "/home/user/PycharmProjects/0480_all_integrated/attic3.py", line 36, in <module>
    exporter = pg.exporters.ImageExporter(view.currentItem)
  File "/home/user/anaconda3/lib/python3.6/site-packages/pyqtgraph/exporters/ImageExporter.py", line 15, in __init__
    tr = self.getTargetRect()
  File "/home/user/anaconda3/lib/python3.6/site-packages/pyqtgraph/exporters/Exporter.py", line 96, in getTargetRect
    return self.item.mapRectToDevice(self.item.boundingRect())
AttributeError: 'NoneType' object has no attribute 'mapRectToDevice'

Answer 1

我在PyQtGraph google forum上交叉引用了我的问题，得到了一个合适的解决方法。

import numpy as np
from PyQt5 import QtWidgets
import pyqtgraph as pg
import pyqtgraph.exporters
from pyqtgraph.Qt import QtCore, QtGui
from pyqtgraph import GraphicsLayoutWidget


class PyQtGraphExportTest(GraphicsLayoutWidget):

    def __init__(self):
        super().__init__()

        self.setWindowTitle('Test pyqtgraph export')
        self.resize(640, 400)

        # Set up a couple of stacked plots
        self.plot1 = self.addPlot(row=0, col=0)
        self.trace1 = self.plot1.plot(np.random.random(10))
        self.plot1.enableAutoRange(pg.ViewBox.XYAxes)

        self.plot2 = self.addPlot(row=1, col=0)
        self.trace2 = self.plot2.plot(np.random.random(10))
        self.plot2.enableAutoRange(pg.ViewBox.XYAxes)

        self.plot3 = self.addPlot(row=2, col=0)
        self.trace3 = self.plot3.plot(np.random.random(10))
        self.plot3.enableAutoRange(pg.ViewBox.XYAxes)

        self.plot1.hideAxis("left")
        self.plot1.hideAxis("bottom")
        self.plot2.hideAxis("left")
        self.plot2.hideAxis("bottom")
        self.plot3.hideAxis("left")
        self.plot3.hideAxis("bottom")



        # Store reference to exporter so it doesn't have to be initialised every
        # time it's called. Note though the window needs to be displayed so
        # mapping from plot to device coordinates is set up, that hasn't
        # happened yet as this GraphicsLayoutWidget is also the Qt app window,
        # so we'll create it later on.
        self.exporter = None

        # Configure a timer to act as trigger event for export. This could be a
        # data acquisition event, button press etc.
        self.timer = QtCore.QTimer()
        self.timer.timeout.connect(self.update_data)
        self.timer.start(2000)

    def update_data(self):
        # Create the exporter if needed, now window is displayed on screen
        if not self.exporter:
            # Here we are passing the exporter the GraphicsLayout object that is
            # the central item (ci) inside this GraphicsLayoutWidget. That in
            # turn contains the two PlotItem objects.
            self.exporter = pg.exporters.ImageExporter(self.ci)
            self.exporter.parameters()['width'] = 640
        # Get some new data, update plot and export
        import time
        my_time = time.time()
        self.trace1.setData(np.random.random(10))
        self.trace2.setData(np.random.random(10))
        self.trace3.setData(np.random.random(10))
        self.exporter.export('exported_image.png')
        print("03:38 ----:", time.time() - my_time)

if __name__ == '__main__':
    import sys

    app = QtWidgets.QApplication(sys.argv)
    window = PyQtGraphExportTest()
    window.show()
    if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
        sys.exit(app.exec_())