Hi Patrick,
you made my day!
This is the framework I already can work with from scratch. Perfect!
0.04 seconds on average per export. Super!
I will post your code as an (unaccepted) answer in stackoverflow, as still
others might see it there and could benefit from it.
Thanks again!
On Wednesday, 12 September 2018 03:06:42 UTC+2, Patrick wrote:
>
> The "entire scene" export item is the GraphicsLayout object that then
> contains the multiple PlotItem objects. Demo code below (Note on Linux you
> can overwrite an open file, so can see exported image being updated in
> realtime, probably can't do that on Windows).
>
> 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)
>
> # 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
> self.trace1.setData(np.random.random(10))
> self.trace2.setData(np.random.random(10))
> self.exporter.export('exported_image.png')
>
> 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_())
>
>
>
>
>
>
> On Wednesday, 12 September 2018 02:03:24 UTC+9:30, GR wrote:
>>
>> Hi Patrick,
>>
>> thanks, that was already helpful.
>>
>> You are right that the call to app.exec_() was missing for a proper
>> display. And with that, indeed, I can execute the export from the gui.
>>
>> My boilerplate for exporting was
>> http://www.pyqtgraph.org/documentation/exporting.html and so I thought I
>> could work without the app.exec_().
>>
>> So perhaps you know what I have to pass as a proper plotItem instance?
>>
>> Thanks in advance!
>>
>> On Tuesday, 11 September 2018 04:29:39 UTC+2, Patrick wrote:
>>>
>>> Hi,
>>> I'm pretty sure you can do this (update plot and export, without plot
>>> being updated on screen), but I think the plot axes still needs to be
>>> displayed somewhere initially so that the mapping from plot to device
>>> coordinates gets set up. Maybe there's a way to do that without showing the
>>> plot window, but I don't know.
>>>
>>> In your example code you never call app.exec_(), so the Qt event loop
>>> never starts, so none of the required initialisation happens. If you run a
>>> normal app with the window displayed, then trigger the export from a
>>> button/timer/event etc, then it should work.
>>>
>>> As an aside, I use pyqtgraph to plot inside my applications due to fast
>>> screen updates and interactivity, but produce output plot files with
>>> matplotlib (as pdf or png). So when the user hits the "save" button, I pass
>>> the data off to a separate matplotlib plotting method as it has prettier
>>> and more flexible plotting options. For performance, you can keep the
>>> matplotlib figure around and just modify the plot data with set_data
>>> methods rather than recreating the whole plot again. If that still isn't
>>> fast enough, then maybe store raw data and analyse/plot afterwards.
>>>
>>> On Tuesday, 11 September 2018 01:53:07 UTC+9:30, GR wrote:
>>>>
>>>> Hi,
>>>>
>>>> I posted a question on stackoverflow:
>>>>
>>>>
>>>> https://stackoverflow.com/questions/52250075/how-does-a-pyqtgraph-export-for-three-subplots-look-like
>>>>
>>>> I am unsure about how much attention it would rise there. Therefore I
>>>> would like to draw your attention to that question.
>>>>
>>>> I hope you do not mind.
>>>>
>>>> If you have an idea how my question can be solved: thanks in advance!
>>>>
>>>> Gerhard
>>>>
>>>>
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