Discrepancy in morphometrics between v3 and v4

Describe the bug When comparing morphometrics obtained in v3 and v4, the solidity and orientation values differ.

To Reproduce I computed morphometrics on the image.png test image located in axondeepseg/test/__test_files__/__test_demo_files__ and indeed every values are the same between versions except solidity and orientation.

[mariehbourget]

Thank you @hermancollin for looking into this! I also agree that we should consider adopting the new convention. Because we are also updating the models with v4, it seems to me that it’s the best possible time to do this.

[hermancollin]

For the solidity, it looks a bit more convoluted. This is how it’s computed:

def solidity(self):
        return self.area / self.area_convex

area_convex is in turn computed using skimage.morphology.convex_hull_image. Not sure what is happening exactly here but in skimage 0.18.0 this function was changed

morphology.convex_hull_image now uses much less memory by checking hull inequalities in sequence (#5020)

Maybe this has something to do with it because the solidity values only differ by about 1% between v3 and v4.

But I agree with @mathieuboudreau that switching to the new convention should be considered.