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pythontreenlpnltktext-parsing

Saving nltk drawn parse tree to image file

enter image description here

Is there any way to save the draw image from tree.draw() to an image file programmatically? I tried looking through the documentation, but I couldn't find anything.

Solution

  • I had exactly the same need, and looking into the source code of nltk.draw.tree I found a solution:

    from nltk import Tree
from nltk.draw.util import CanvasFrame
from nltk.draw import TreeWidget

cf = CanvasFrame()
t = Tree.fromstring('(S (NP this tree) (VP (V is) (AdjP pretty)))')
tc = TreeWidget(cf.canvas(),t)
cf.add_widget(tc,10,10) # (10,10) offsets
cf.print_to_file('tree.ps')
cf.destroy()

    The output file is a postscript, and you can convert it to an image file using ImageMagick on terminal:

    $ convert tree.ps tree.png

    I think this is a quick and dirty solution; it could be inefficient in that it displays the canvas and destroys it later (perhaps there is an option to disable display, which I couldn't find). Please let me know if there is any better way.