Re: [Matplotlib-users] Arc reporting bogus bounding box?

[Jason S. <jas...@gm...>]

On Sun, Oct 4, 2009 at 10:57 PM, Jae-Joon Lee <lee...@gm...> wrote:
> MPL, by default, does not do any clipping. So, i'm not sure why the
> extent of the circle matters (I think even the bbox_inches option does
> not take care of that) . Everything should be fine as far as you
> create a figure in an appropriate size. Changing the suplotplot
> parameters (or something similar) is not your option?

> If possible, can you post a simplified version of your code that
> demonstrate the problem?

Sure:
-------- bounds.py ---------
#!/usr/bin/python
import matplotlib
import pylab

if __name__ == '__main__':
    pylab.clf()
    ax = pylab.axes([0,0,1,1])
    ax.add_line(matplotlib.lines.Line2D((2, 5), (0.75, 6)))
    ax.add_patch(matplotlib.patches.Arc((2, 0), 1.5, 1.5, 0.0, 0,
180.0, fill=False))
    ax.axis('equal')
    pylab.savefig("fig-a.pdf", bbox_inches='tight', pad_inches=0)
--------------------------------

What this does is make a stupid little picture of a hemi-circle and
and line going off somewhere. At any rate, the y dimensions of this
image are something like [-0.75, 6], while I'd expect it to be [0, 6]
- the 'imaginary' lower half of the circle is being used to compute
the final axes size. The y dimensions do no change if I choose
ax.axis('tight')

While I'm at it, I might as well as about image dimensions vs. axes limits.

If I change ax.axis('equal') manually to the correct bounding box of
the visible stuff (i.e. ax.axis([1.25, 5, 0, 6])), I then get an image
that is distorted, presumably to fit some pre-set aspect ratio. Is
there a way to fix this, too? I guess what I'd like is a way to say:
"When you save or render this image, set the output image dimensions
to be appropriate to aspect ratio x (usually 1:1 for me) and the
current axis setting"

I've used matplotlib for more than a few projects, but this aspect of
it has eluded me.

Thanks for all your help,
Jason