How do I integrate the pyqtgraph image example into a class?

I am trying to integrate the pyqtgraph example into a class. However, since the example uses "global" to acces important methods, I am having trouble translating it into a class.

The example:

import initExample ## Add path to library (just for examples; you do not need this)

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


# Interpret image data as row-major instead of col-major
pg.setConfigOptions(imageAxisOrder='row-major')

pg.mkQApp()
win = pg.GraphicsLayoutWidget()
win.setWindowTitle('pyqtgraph example: Image Analysis')

# A plot area (ViewBox + axes) for displaying the image
p1 = win.addPlot()

# Item for displaying image data
img = pg.ImageItem()
p1.addItem(img)

# Custom ROI for selecting an image region
roi = pg.ROI([-8, 14], [6, 5])
roi.addScaleHandle([0.5, 1], [0.5, 0.5])
roi.addScaleHandle([0, 0.5], [0.5, 0.5])
p1.addItem(roi)
roi.setZValue(10)  # make sure ROI is drawn above image

# Isocurve drawing
iso = pg.IsocurveItem(level=0.8, pen='g')
iso.setParentItem(img)
iso.setZValue(5)

# Contrast/color control
hist = pg.HistogramLUTItem()
hist.setImageItem(img)
win.addItem(hist)

# Draggable line for setting isocurve level
isoLine = pg.InfiniteLine(angle=0, movable=True, pen='g')
hist.vb.addItem(isoLine)
hist.vb.setMouseEnabled(y=False) # makes user interaction a little easier
isoLine.setValue(0.8)
isoLine.setZValue(1000) # bring iso line above contrast controls

# Another plot area for displaying ROI data
win.nextRow()
p2 = win.addPlot(colspan=2)
p2.setMaximumHeight(250)
win.resize(800, 800)
win.show()


# Generate image data
data = np.random.normal(size=(200, 100))
data[20:80, 20:80] += 2.
data = pg.gaussianFilter(data, (3, 3))
data += np.random.normal(size=(200, 100)) * 0.1
img.setImage(data)
hist.setLevels(data.min(), data.max())

# build isocurves from smoothed data
iso.setData(pg.gaussianFilter(data, (2, 2)))

# set position and scale of image
img.scale(0.2, 0.2)
img.translate(-50, 0)

# zoom to fit imageo
p1.autoRange()  


# Callbacks for handling user interaction
def updatePlot():
    global img, roi, data, p2
    selected = roi.getArrayRegion(data, img)
    p2.plot(selected.mean(axis=0), clear=True)

roi.sigRegionChanged.connect(updatePlot)
updatePlot()

def updateIsocurve():
    global isoLine, iso
    iso.setLevel(isoLine.value())

isoLine.sigDragged.connect(updateIsocurve)


## Start Qt event loop unless running in interactive mode or using     pyside.
if __name__ == '__main__':
    import sys
    if (sys.flags.interactive != 1) or not hasattr(QtCore,     'PYQT_VERSION'):
        QtGui.QApplication.instance().exec_()

What I tried: (only changed parts)

    def updatePlot(img, roi, data, p2):
            #global img, roi, data, p2
            selected = roi.getArrayRegion()
            p2.plot(selected.mean(axis=0), clear=True)

    roi.sigRegionChanged.connect(updatePlot(img, roi, data, p2))    
    updatePlot(img, roi, data, p2)


    def updateIsocurve(isoLine, iso):
    # global isoLine, iso
         so.setLevel(isoLine.value())

    isoLine.sigDragged.connect(updateIsocurve(isoLine, iso))

This gives an error, since the "img" object I am giving it instead of accessing it through "global" seems to be of type None.

I don't know how to give the update function access to the necessary objects.

Solution

Make all the variables into instance variables by using self

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

class ImageWidget(QtGui.QWidget):
    def __init__(self, parent=None):
        super(ImageWidget, self).__init__(parent)

        # Interpret image data as row-major instead of col-major
        pg.setConfigOptions(imageAxisOrder='row-major')

        pg.mkQApp()
        self.win = pg.GraphicsLayoutWidget()
        self.win.setWindowTitle('pyqtgraph example: Image Analysis')

        # A plot1 area (ViewBox + axes) for displaying the image
        self.plot1 = self.win.addPlot()

        # Item for displaying image data
        self.item = pg.ImageItem()
        self.plot1.addItem(self.item)

        # Custom ROI for selecting an image region
        self.ROI = pg.ROI([-8, 14], [6, 5])
        self.ROI.addScaleHandle([0.5, 1], [0.5, 0.5])
        self.ROI.addScaleHandle([0, 0.5], [0.5, 0.5])
        self.plot1.addItem(self.ROI)
        self.ROI.setZValue(10)  # make sure ROI is drawn above image

        # Isocurve drawing
        self.iso = pg.IsocurveItem(level=0.8, pen='g')
        self.iso.setParentItem(self.item)
        self.iso.setZValue(5)

        # Contrast/color control
        self.hist = pg.HistogramLUTItem()
        self.hist.setImageItem(self.item)
        self.win.addItem(self.hist)

        # Draggable line for setting isocurve level
        self.isoLine = pg.InfiniteLine(angle=0, movable=True, pen='g')
        self.hist.vb.addItem(self.isoLine)
        self.hist.vb.setMouseEnabled(y=False) # makes user interaction a little easier
        self.isoLine.setValue(0.8)
        self.isoLine.setZValue(1000) # bring iso line above contrast controls

        # Another plot1 area for displaying ROI data
        self.win.nextRow()
        self.plot2 = self.win.addPlot(colspan=2)
        self.plot2.setMaximumHeight(250)
        self.win.resize(800, 800)
        self.win.show()

        # Generate image self.data
        self.data = np.random.normal(size=(200, 100))
        self.data[20:80, 20:80] += 2.
        self.data = pg.gaussianFilter(self.data, (3, 3))
        self.data += np.random.normal(size=(200, 100)) * 0.1
        self.item.setImage(self.data)
        self.hist.setLevels(self.data.min(), self.data.max())

        # build isocurves from smoothed self.data
        self.iso.setData(pg.gaussianFilter(self.data, (2, 2)))

        # set position and scale of image
        self.item.scale(0.2, 0.2)
        self.item.translate(-50, 0)

        # zoom to fit imageo
        self.plot1.autoRange()  

        self.ROI.sigRegionChanged.connect(self.updatePlot)
        self.updatePlot()

        self.isoLine.sigDragged.connect(self.updateIsocurve)

    # Callbacks for handling user interaction
    def updatePlot(self):
        selected = self.ROI.getArrayRegion(self.data, self.item)
        self.plot2.plot(selected.mean(axis=0), clear=True)

    def updateIsocurve(self):
        self.iso.setLevel(self.isoLine.value())

## Start Qt event loop unless running in interactive mode or using     pyside.
if __name__ == '__main__':

    app = QtGui.QApplication([])
    app.setStyle(QtGui.QStyleFactory.create("Cleanlooks"))

    image_widget = ImageWidget()

    import sys
    if (sys.flags.interactive != 1) or not hasattr(QtCore,     'PYQT_VERSION'):
        QtGui.QApplication.instance().exec_()