CODEWITHSUNDEEP
pythonmatplotlib
r_31415
r_31415

Reputation: 8982

Coordinates of box of annotations in matplotlib

How can I get the coordinates of the box displayed in the following plot?

enter image description here

fig, ax = subplots()
x = ax.annotate('text', xy=(0.5, 0), xytext=(0.0,0.7), 
                ha='center', va='bottom',
                bbox=dict(boxstyle='round', fc='gray', alpha=0.5),
                arrowprops=dict(arrowstyle='->', color='blue'))

I tried to inspect the properties of this object, but I couldn't find something suited to this purpose. There is a property called get_bbox_patch() which could be on the right track, however, I get results in a different coordinate system (or associated to a different property)

y = x.get_bbox_patch()
y.get_width()
63.265625

Thanks a lot!

Upvotes: 6

Views: 5898

Answers (2)

tacaswell
tacaswell

Reputation: 87496

ax.figure.canvas.draw()
bbox = x.get_window_extent()

will return a Bbox object for your text in display units (the draw is necessary so that the text is rendered and actually has a display size). You can then use the transforms to convert it to which ever coordinate system you want. Ex

bbox_data = ax.transData.inverted().transform(bbox)

Upvotes: 6

oz123
oz123

Reputation: 28868

To your questions there is also a a pre-question:

  • When you write How can I get the coordinates of the box displayed in the following plot?, which coordinate system you mean?

By default annotate is done using xytext = None, defaults to xy, and if textcoords = None, defaults to xycoords.

Since you didn't specify the coordinate system. Your annotation is on the default system. You could specify the data coordinates, which for some purposes is good enough:

x = ax.annotate('text', xy=(0.5, 0), xytext=(0.0,0.7), 
                ha='center', va='bottom', textcoords='data', xycoords="data",
                bbox=dict(boxstyle='round', fc='gray', alpha=0.5),
                arrowprops=dict(arrowstyle='->', color='blue'))

To find the coordinate system, you can do:

In [39]: x.xycoords
Out[39]: 'data'

and to get the coordinates:

In [40]: x.xytext
Out[40]: (0.0, 0.7)

In [41]: x.xy
Out[41]: (0.5, 0)

P.S. not directly related, but the output is from IPython, if you still don't use it, it can boost how you develop in Python and use matplotlib. Give it a try.

Upvotes: 1

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