Re: [Matplotlib-users] Saving as eps file shifts image?

[Jenna L. <je...@as...>]

That looks fine to me too, but if you plot that as one subplot in a 5x5 array
of subplots or more, then you can see the shift I am talking about in the
eps file.  Example:

import matplotlib.pyplot as plt
import numpy as np

arr = np.zeros((11, 11), dtype="d")
arr[3,3]=1
plt.figure(1)
plt.subplot(10,10,1)
im = plt.imshow(arr, interpolation="nearest", origin="lower")
cont = plt.contour(arr, levels=[0.5])
plt.savefig("a.eps")


Jae-Joon Lee wrote:
> 
> I tried a simple array (see the code below) but cannot reproduce the
> problem you reported.
> 
> import matplotlib.pyplot as plt
> import numpy as np
> 
> arr = np.zeros((11, 11), dtype="d")
> arr[3,3]=1
> im = plt.imshow(arr, interpolation="nearest", origin="lower")
> cont = plt.contour(arr, levels=[0.5])
> plt.savefig("a.eps")
> 
> Do you still see the shift with the above example code?
> And what version of matplotlib are you using?
> 
> If possible, please post a complete script with the data (use a
> mock-up data if you want)?
> Regards,
> 
> -JJ
> 
> 
> 
> On Fri, Jul 23, 2010 at 12:16 AM, Jenna Lemonias
> <je...@as...> wrote:
>> No, I don't think the issue is a flip in the y-axis.  I have a number of
>> different examples of this, and many in which the contour is an ellipse
>> so I
>> can tell that the overall positioning is correct.  It seems like
>> something
>> is going wrong only when I save the image...  Thanks for the suggestion
>> though!
>>
>> Jenna
>>
>> On Wed, Jul 21, 2010 at 3:40 PM, Jenna Lemonias
>> <je...@as...>wrote:
>>
>>> I am trying to save a matplotlib 2d array image with an overlaid contour
>>> as
>>> an eps file.  The contour appears to be shifted with respect to the
>>> image
>>> underneath in the eps file, particularly when I zoom in on the image.
>>> This
>>> shift is not noticeable in the plot within matplotlib.
>>>
>>> I am using imshow to display the image.  The contour is created by
>>> plotting
>>> a list of closely-spaced x,y coordinates.  The attached file
>>> matplotlib.png
>>> is a screenshot of the (zoomed-in) image as displayed by matplotlib. 
>>> The
>>> attached file epsfile.png is a screenshot of the (zoomed-in) eps file.
>>> When
>>> I save this image as an eps file, it is actually 1 of 20 subplots and
>>> the
>>> shift is noticeable in each subplot.
>>>
>>> Thanks in advance for your help!
>>>
>>> Jenna
>>>
>>>
>> Just as a wild guess, could this actually be an issue with how imshow
>> uses
>> the upper-left corner for (0,0)?  I have seen 1-pixel shifts before, but
>> this shift is a little dramatic and I am left wondering if what we are
>> really seeing is that the contour that is desired should actually be
>> fliped
>> in the y-axis?
>>
>> Maybe you could try another example where you try to draw a contour
>> further
>> away from the center of the image and see if it still goes in the spot
>> you
>> expect it to be?
>>
>> Ben Root
>>
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