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Inverted imshow using Cairo backend #7156

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QuLogic opened this issue Sep 22, 2016 · 4 comments
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Inverted imshow using Cairo backend #7156

QuLogic opened this issue Sep 22, 2016 · 4 comments
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backend: cairo
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v2.0.0

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@QuLogic
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QuLogic commented Sep 22, 2016

In testing some stuff for #7151, I realized that the Cairo backend inverts images plotted using imshow.

import matplotlib as mpl
mpl.use('Cairo')
import numpy as np
import matplotlib.pyplot as plt

a = np.random.randn(3,3)

im1 = plt.imshow(a, extent = [0,1,0,1])
plt.xlim(0,2.2)
plt.ylim(0,2.2)

plt.savefig('test.png')

It doesn't really matter if saving as png or pdf, the outcome is the same. With Agg, the image appears in the lower left corner:
test
With Cairo, the image appears in the upper left corner:
test

It worked correctly with mpl 1.4.3 and is broken with 1.5.0, but bisection is next to impossible because the Cairo backend was broken for a very long time.
@QuLogic
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QuLogic commented Oct 10, 2016

I'm going to ping @jenshnielsen who seems to have last had contact with the cairo backend.

@tacaswell tacaswell added this to the 2.0 (style change major release) milestone Oct 11, 2016
@tacaswell
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I can not reproduce this on 2.x with py3.5 and cairocffi

test

Please ping to have this re-opened if there is some combination of 2.x + py + cairo binding that fails.

@QuLogic
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QuLogic commented Oct 12, 2016

Oh, I thought I tested with v2.x at some point, but it looks like you're right. It appears to have been fixed with the ever-growing list of things from #5718.

@tacaswell
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The dragon infested rabbit holes are paying for them selves in recovered technical debt.

@QuLogic QuLogic mentioned this issue Dec 11, 2016
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