Hi Patrick,
thanks a lot! I will use that.
Wonderful - again!
On Tuesday, 18 September 2018 04:40:19 UTC+2, Patrick wrote:
>
> Hi,
>
> I think there is a bug somewhere, where the first call to setData()
> doesn't result in the view range being updated. Your code is working fine,
> the plot is being updated with the correct data, but the axes scales aren't
> correct on the first call.
>
> Without spending time tracing through why the ranges aren't being updated,
> a simple workaround would be to manually trigger the update by inserting
> "self.plot.autoRange()" after your self.spectrum.setData(data) line. Not
> ideal, but seems to work.
>
> Patrick
>
>
> On Tuesday, 18 September 2018 05:54:18 UTC+9:30, GR wrote:
>>
>>
>> Hi,
>>
>> I am using the following code to generate png files with PyQtGraph.
>>
>> The code works quite well, but unfortunately, the first loop / picture
>> ("0exported_image.png", that is: runner = 0) does not have any data in the
>> output picture (respectively: has only default values in the exported
>> graph).
>> I additionally set a manual breakpoint in "update_data" and looked at
>> the attributes of the class instance for runner = 0 and runner >0. It
>> strikes that at several parts of the object tree the "picture" is set for
>> runner >0, but is not for runner = 0:
>>
>> "picture": {
>> "py/object": "PyQt5.QtGui.QPicture"
>> },
>>
>>
>>
>> This is the code I use. Does anybody have an idea what could be the
>> reason for this?
>>
>> Thanks in advance.
>>
>> import numpy as np
>> from PyQt5 import QtWidgets
>> from PyQt5.QtCore import pyqtSignal, pyqtSlot
>> import pyqtgraph as pg
>> import pyqtgraph.exporters
>> from pyqtgraph.Qt import QtCore, QtGui
>> from pyqtgraph import GraphicsLayoutWidget
>> from threading import Thread, Event
>> import time
>>
>>
>> # Routine to acquire and serve data
>> # This might be a camera driver, notifying when a new frame is available
>> def generate_data(callback, threadkill):
>> # while not threadkill.is_set():
>> # width = 1600
>> # data = np.zeros(width)
>> # runner = int(np.random.random()*5)
>> # data.fill(runner)
>> # callback(data, runner)
>> # time.sleep(0.01)
>> for runner in range(5):
>> width = 1600
>> data = np.zeros(width)
>> data.fill(runner)
>> my_var = callback(data, runner)
>> time.sleep(0.01)
>> print("callback called")
>>
>> # threadkill.set()
>> # # sys.exit(1)
>>
>>
>> class PyQtGraphTest(GraphicsLayoutWidget):
>> # Signal to indicate new data acquisition
>> # Note: signals need to be defined inside a QObject class/subclass
>> data_acquired = pyqtSignal(np.ndarray, int)
>>
>> def __init__(self):
>> super().__init__()
>> self.exporter = None
>>
>> self.setWindowTitle('Test pyqtgraph paint signals')
>> self.resize(640, 400)
>> self.plot = self.addPlot()
>> self.spectrum = self.plot.plot()
>> self.plot.enableAutoRange(pg.ViewBox.XYAxes)
>>
>> # Connect the signal
>> self.data_acquired.connect(self.update_data)
>>
>> # Make and start the background thread to acquire data
>> # Pass it the signal.emit as the callback function
>> self.threadkill = Event()
>> self.thread = Thread(target=generate_data,
>> args=(self.data_acquired.emit, self.threadkill))
>> self.thread.start()
>>
>> self.thread.join()
>> # my_var = self.thread.isAlive()
>> # print("my_var:", my_var)
>> # self.threadkill.set()
>> # print("fin")
>>
>> # Kill our data acquisition thread when shutting down
>> def closeEvent(self, close_event):
>> self.threadkill.set()
>>
>> # Slot to receive acquired data and update plot
>> @pyqtSlot(np.ndarray, int)
>> def update_data(self, data, runner):
>> 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
>>
>> self.spectrum.setData(data)
>> self.exporter.export(str(runner) + 'exported_image.png')
>> print("exported image")
>>
>>
>> if __name__ == '__main__':
>> import sys
>>
>> app = QtWidgets.QApplication(sys.argv)
>> window = PyQtGraphTest()
>> window.show()
>> if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
>> sys.exit(app.exec_())
>>
>> print("fin2")
>>
>>
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