TST: Increase tolerance of some tests for aarch64

Some tests differ from expected result on aarch64 by more than the
expected tolerance.  The generated images however remain visually
similar.

The differences appear to be at borders of colours for images,
i.e. edges of fonts, between transitions of colours, etc. and is
possibly due to FP rounding differences at those points.

Bump up tolerance of these tests by a wee bit so that they pass on
aarch64.

Author: siddhesh

lib/matplotlib/tests/test_backend_pgf.py

@@ -6,6 +6,7 @@
 
 import numpy as np
 import pytest
+import platform
 
 import matplotlib as mpl
 import matplotlib.pyplot as plt
@@ -165,7 +166,8 @@ def test_pathclip():
 # test mixed mode rendering
 @needs_xelatex
 @pytest.mark.backend('pgf')
-@image_comparison(['pgf_mixedmode.pdf'], style='default')
+@image_comparison(['pgf_mixedmode.pdf'], style='default',
+                  tol={'aarch64': 1.086}.get(platform.machine(), 0.0))
 def test_mixedmode():
     rc_xelatex = {'font.family': 'serif',
                   'pgf.rcfonts': False}

lib/matplotlib/tests/test_pickle.py

@@ -40,7 +40,7 @@ def test_simple():
 
 
 @image_comparison(['multi_pickle.png'], remove_text=True, style='mpl20',
-                  tol={'aarch64': 0.02}.get(platform.machine(), 0.0))
+                  tol={'aarch64': 0.082}.get(platform.machine(), 0.0))
 def test_complete():
     fig = plt.figure('Figure with a label?', figsize=(10, 6))
 

lib/matplotlib/tests/test_usetex.py

@@ -1,4 +1,5 @@
 import pytest
+import platform
 
 import matplotlib as mpl
 from matplotlib.testing.decorators import check_figures_equal, image_comparison
@@ -14,7 +15,7 @@ def usetex():
 
 @image_comparison(baseline_images=['test_usetex'],
                   extensions=['pdf', 'png'],
-                  tol=0.3)
+                  tol={'aarch64': 2.868}.get(platform.machine(), 0.3))
 def test_usetex():
     fig = plt.figure()
     ax = fig.add_subplot(111)

lib/mpl_toolkits/tests/test_axisartist_grid_helper_curvelinear.py

@@ -16,7 +16,8 @@
     GridHelperCurveLinear
 
 
-@image_comparison(['custom_transform.png'], style='default', tol=0.03)
+@image_comparison(['custom_transform.png'], style='default',
+                  tol={'aarch64': 0.034}.get(platform.machine(), 0.03))
 def test_custom_transform():
     class MyTransform(Transform):
         input_dims = 2