On 06/11/2010 02:38 PM, jason-s...@creativetrax.com wrote:
> On 6/11/10 1:02 PM, Michael Droettboom wrote:
>
>>
>>> It appears that the difficulty is that quantization is exposed at the
>>> python level only for collections, via iter_segments.
>>>
>>>
>>>
>> Sort of. Lines (but none of the other artists) follow what is set by
>> "set_snap" (the use of two terms for the same thing is also a problem,
>> of course). This needs to be extended to other artists (and other
>> relevant backend methods other than draw_path, if necessary). But I
>> think for convenience, it should also be a global rcParam.
>>
> I think a work-around, then (at least it seems to work for me), is
> setting both snap to False and antialiased to False for the spines.
> That won't solve the issue for other horizontal lines, but at least it
> takes care of having the correct origin for the intersection of the
> spines. (Correct me if I'm wrong, of course!)
>
> from matplotlib import pyplot as plt
> import numpy as np
> fig = plt.figure()
> ax = fig.add_subplot(1,1,1, aspect='equal')
> line1=ax.plot([-1,1],[0,0], color='blue')
> line2=ax.plot([-1,1],[-1,1], color='red',zorder=5)
> ax.set_xlim(-1.1,1.1)
> ax.set_ylim(-1.1,1.1)
> ax.spines['left'].set_position('zero')
> ax.spines['left'].set_snap(False)
> ax.spines['left'].set_antialiased(False)
> ax.spines['right'].set_color('none')
> ax.spines['bottom'].set_position('zero')
> ax.spines['bottom'].set_snap(False)
> ax.spines['bottom'].set_antialiased(False)
> ax.spines['top'].set_color('none')
> ax.xaxis.set_ticks_position('bottom')
> ax.yaxis.set_ticks_position('left')
> fig.savefig('test.png',dpi=100)
>
I've committed a patch that provides a global snap setting in r8415.
Set the rcParam "path.snap" to False to turn off all snapping (though it
should be equivalent to your "set_snap" calls above -- just possibly
more convenient).
However, I think turning anti-aliasing off will give you the same
problem at some scales, as anti-aliasing has basically the same effect
as snapping: rounding to integral pixel values. Try an odd dpi such as
"67" for example.
Mike
--
Michael Droettboom
Science Software Branch
Space Telescope Science Institute
Baltimore, Maryland, USA
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