Isocurve example from pyqtgraph.examples works on Windows but not Linux!

[david_the_plotter]

Hi

I am currently developing a plotting routine involving an isocurve just like the one in one of the examples found at pyqtgraph.examples. I made the program which works beautifully on windows. However, when running the same program (including the example) on a Linux no isocurve shows and you get the following error message:

Traceback (most recent call last):

  File "/usr/lib/python2.7/dist-packages/pyqtgraph/graphicsItems/IsocurveItem.py", line 114, in paint

    self.generatePath()

  File "/usr/lib/python2.7/dist-packages/pyqtgraph/graphicsItems/IsocurveItem.py", line 103, in generatePath

    lines = fn.isocurve(self.data, self.level, connected=True, extendToEdge=True)

  File "/usr/lib/python2.7/dist-packages/pyqtgraph/functions.py", line 1513, in isocurve

    index += fields[i,j] * 2**vertIndex

TypeError: Cannot cast ufunc add output from dtype('int64') to dtype('uint8') with casting rule 'same_kind'

Any ideas? It would be great to get this issue resolved so both Windows- and Linux-users could enjoy this feature!

Regards

david_the_plotter