Sorry, I was too fast in my reply.
When I save the figure, the png output is ok while the pdf is displaying some
kind of interpolation with the image.
import numpy as np
import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt
n = 16
fig = plt.figure(figsize=(6,6))
Z = np.array(([0,1]*(n//2) + [1,0]*(n//2))*(n//2)).reshape(n,n)
plt.imshow(Z, interpolation='none', cmap=plt.cm.gray, extent=[0,n,0,n],
alpha=.25)
plt.xticks(np.arange(0,n), [])
plt.yticks(np.arange(0,n), [])
plt.grid(ls='solid')
plt.savefig('pylab-grid.png')
plt.savefig('pylab-grid.pdf')
plt.show()
Just for the record, "Skim", "Preview" and "Adobe Reader" on OSX do not give
the same output on the saved pdf.
"Adobe Reader" displays the expected result (same as saved png) while "Preview"
and "Skim" are apparently trying to make some (bad) interpolation of the
checkboard image.
Nicolas
On Oct 30, 2012, at 7:52 , Nicolas Rougier wrote:
>
>
> You're right. Using 'none' interpolation seems to solve the problem. Good to
> know !
>
> One last question, why is the 'none' interpolation restricted to Agg/PS/pdf ?
>
>
> Nicolas
>
>
>
> On Oct 30, 2012, at 6:53 , Jae-Joon Lee wrote:
>
>> On Tue, Oct 30, 2012 at 12:25 AM, Nicolas Rougier
>> <nicolas.roug...@inria.fr> wrote:
>>>
>>>
>>> Thanks for testing.
>>>
>>> If I zoom at any line cross, the lines are definitely at the wrong place
>>> for me.
>>
>> As jules hummon commented, I see lines in right places when I zoom in.
>>
>>> As for screen aliasing I'm not sure since both the png and pdf seems to be
>>> wrong in my case.
>>
>> It still can be some aliasing-related issue. Note that with
>> interpolation="nearest", the images are rasterized with given dpi even
>> if you save the figure as pdf.
>> The agg backend tries to adjust the location of lines and images so
>> that they are well-aligned with the pixels, and the issue seems to be
>> related with that behavior.
>>
>> In my case, using interpolation="none" worked out okay. So give it a try.
>>
>> Regards,
>>
>> -JJ
>>
>>
>>> Weird !
>>>
>>>
>>> Nicolas
>>>
>>>
>>> On Oct 29, 2012, at 15:40 , jules hummon wrote:
>>>
>>>> Nicolas
>>>>
>>>> I get that too, (with your script and various things in my work).
>>>> But if you zoom in, the lines are in the right place. Is it
>>>> some kind of screen aliasing?
>>>>
>>>> Jules
>>>>
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