[Insight-users] reproducible bug in CannyEdgeDetectionImageFilter

[Charl Botha]

Dear all,

Running the attached Python script on
Insight/Testing/Data/Input/cthead1.png yields 4 images on disc, of
which canny_t0.png and canny_t0_after.png should be identical, as they
are using the same thresholds, and otherwise identical parameters.
However, they are wildly different, see the attached images.

In short, the canny filter's behaviour changes depending on whether it
has been freshly instantiated or whether it has been used with a
different parameter setting before.  Setting the threshold back to a
previous value after having executed the filter with different values
will yield incorrect results.

Is this a bug, or am I expecting too much from this filter? :)

Thanks,
Charl
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