[Matplotlib-users] Plotting boundaries of segmented data

rwleo peter.leitner at uni-graz.at
Wed Dec 7 11:59:56 EST 2016


I am trying to plot a 2-D array with segmentation data from a fluid flow.
The data structure is continuous which means that the segments are connected
regions, like in the picture below:
I use
plt.imshow(seg, cmap="Greys")
which returns a black area on a white background. What I would like to
achieve instead is to plot only the boundary as a black curve, like when
plotting a shape with pylab setting edgecolor=black and facecolor=white.
Unfortunately, having the data in matrix format I am not sure whether this
can easily be achieved without writing a separate function that detects
whether a pixel belongs to the border or the interior. Is there an
alternative to the imshow function which does this simply by setting some

Secondly I would like to smoothen the boundary curve which looks quite
"rectangular" due to the coarse segmentation algorithm that has been applied
to the fluid flow data. Can this be done with interp2d, if the segments are
not based on an analytical expression?

Many thanks in advance!

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