Regression: imshow on geo axes produces an empty plot in matplotlib 2.0.0

Bug summary

In Matplotlib 1.5.3, it was possible to use imshow on geo axes (e.g. the mollweide projection defined in matplotlib.projections.geo. In Matplotlib 2.0.0, this produces a blank plot.

Code for reproduction

Here is an example that worked in 1.5.3.

from matplotlib import pyplot as plt
import numpy as np

lon = np.linspace(-np.pi, np.pi)
lat = np.linspace(-np.pi/2, np.pi/2)
lon, lat = np.meshgrid(lon, lat)

ax = plt.axes(projection='mollweide')
ax.grid()
ax.imshow(lon, extent=[-np.pi, np.pi, -np.pi/2, np.pi/2], aspect=ax.get_aspect())
plt.savefig('test.png')

Actual outcome

This is the output on Matplotlib 2.0.0: blank axes.

Expected outcome

This was the output in Matplotlib 1.5.3.

Matplotlib version

Installed from MacPorts on OS X 10.11.6 "El Capitan". Port versions:

py27-matplotlib @1.5.3_0+cairo
py27-matplotlib @2.0.0_0+cairo

It appears that in 1.5.3 the image was being created in Cartesian coordinates and then clipped to the projection. Is this what you want?

Yes.

@mdboom

That seems like fundamentally incorrect behavior, doesn't it? Wouldn't most users expect that if anything, imshow with a projection would warp the image to that projection? It's never done that, though. In 2.0 its behavior with a log scale on one or both axes has changed so that it does map the image to the scale, but I think that its behavior with a non-affine projection has always been undefined. If so, it should raise an error. Alternatively, I suppose it could warn and drop back to the 1.5.x behavior. Comments, @mdboom?

I was looking through past PRs... did this change occur in #5718?

yes, that is the rework that Eric is referring to.

…

On Mon, Jan 23, 2017 at 5:04 PM, Leo Singer ***@***.***> wrote: I was looking through past PRs... did this change occur in #5718 <#5718>? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#7903 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AARy-F-GjvXUZW3O-sXcDqGT0iE0cRvwks5rVSPRgaJpZM4Lp_U0> .

Oh, OK! I modified my test code to use ax.imshow(..., extent=[0, 1, 0, 1], transform=ax.transAxes):

#!/usr/bin/env python
from matplotlib import pyplot as plt
import numpy as np

lon = np.linspace(-np.pi, np.pi)
lat = np.linspace(-np.pi/2, np.pi/2)
lon, lat = np.meshgrid(lon, lat)

ax = plt.axes(projection='mollweide')
ax.grid()
ax.imshow(lon, extent=[0, 1, 0, 1], aspect=ax.get_aspect(), transform=ax.transAxes)
plt.savefig('test.png')

And it works now:

Adapt bayestar_plot_allsky and friends to matplotlib 2.0.0

Oh, OK! I modified my test code to use ax.imshow(..., extent=[0, 1, 0, 1], transform=ax.transAxes):

Was this just a latent bug in my own code that was revealed by the transition to 2.0.0? If so, then we can close this issue.

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Regression: imshow on geo axes produces an empty plot in matplotlib 2.0.0 #7903

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Regression: imshow on geo axes produces an empty plot in matplotlib 2.0.0 #7903

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efiring commented on Jan 23, 2017

lpsinger commented on Jan 23, 2017

efiring commented on Jan 23, 2017

lpsinger commented on Jan 23, 2017

WeatherGod commented on Jan 23, 2017

lpsinger commented on Jan 23, 2017

lpsinger commented on Jan 24, 2017

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