Update corner hist2d to match axis background color (dfm#196)

* Update corner hist2d to match axis background color

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* Update default color to match axes

Default line color now matches axes 'edgecolor' instead of being set to 'black'.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Update corner.py

Change default color from black ('k') to None.

* Update arviz_corner.py

Change default color from black ('k') to None.

* Update core.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Added hist2d tests for color match

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Update default linecolor to ytick color

* Update hist2d tests

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

src/corner/arviz_corner.py

@@ -46,7 +46,7 @@ def arviz_corner(
     # Original corner parameters
     range=None,
     weights=None,
-    color="k",
+    color=None,
     hist_bin_factor=1,
     smooth=None,
     smooth1d=None,

src/corner/core.py

@@ -11,6 +11,7 @@
 import copy
 import logging
 
+import matplotlib
 import numpy as np
 from matplotlib import pyplot as pl
 from matplotlib.colors import LinearSegmentedColormap, colorConverter
@@ -27,7 +28,7 @@ def corner_impl(
     bins=20,
     range=None,
     weights=None,
-    color="k",
+    color=None,
     hist_bin_factor=1,
     smooth=None,
     smooth1d=None,
@@ -171,6 +172,10 @@ def corner_impl(
                 "Dimension mismatch between hist_bin_factor and " "range"
             )
 
+    # Set up the default plotting arguments.
+    if color is None:
+        color = matplotlib.rcParams["ytick.color"]
+
     # Set up the default histogram keywords.
     if hist_kwargs is None:
         hist_kwargs = dict()
@@ -545,21 +550,24 @@ def hist2d(
 
     # Set up the default plotting arguments.
     if color is None:
-        color = "k"
+        color = matplotlib.rcParams["ytick.color"]
 
     # Choose the default "sigma" contour levels.
     if levels is None:
         levels = 1.0 - np.exp(-0.5 * np.arange(0.5, 2.1, 0.5) ** 2)
 
+    # This is the base color of the axis (background color)
+    base_color = ax.get_facecolor()
+
     # This is the color map for the density plot, over-plotted to indicate the
     # density of the points near the center.
     density_cmap = LinearSegmentedColormap.from_list(
-        "density_cmap", [color, (1, 1, 1, 0)]
+        "density_cmap", [color, colorConverter.to_rgba(base_color, alpha=0.0)]
     )
 
     # This color map is used to hide the points at the high density areas.
-    white_cmap = LinearSegmentedColormap.from_list(
-        "white_cmap", [(1, 1, 1), (1, 1, 1)], N=2
+    base_cmap = LinearSegmentedColormap.from_list(
+        "base_cmap", [base_color, base_color], N=2
     )
 
     # This "color map" is the list of colors for the contour levels if the
@@ -662,7 +670,7 @@ def hist2d(
             Y2,
             H2.T,
             [V.min(), H.max()],
-            cmap=white_cmap,
+            cmap=base_cmap,
             antialiased=False,
         )
 

src/corner/corner.py

@@ -21,7 +21,7 @@ def corner(
     # Original corner parameters
     range=None,
     weights=None,
-    color="k",
+    color=None,
     hist_bin_factor=1,
     smooth=None,
     smooth1d=None,

tests/test_hist2d.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 
+import matplotlib
 import numpy as np
 import pytest
 from matplotlib import pyplot as pl
@@ -60,6 +61,57 @@ def test_color():
     _run_hist2d("color", color="g")
 
 
+@image_comparison(
+    baseline_images=["backgroundDark"], remove_text=True, extensions=["png"]
+)
+def test_backgroundDark():
+    pl.style.use("dark_background")
+    _run_hist2d("backgroundDark")
+    pl.style.use("default")
+
+
+@image_comparison(
+    baseline_images=["backgroundDark2"], remove_text=True, extensions=["png"]
+)
+def test_backgroundDark2():
+    pl.style.use("dark_background")
+    _run_hist2d("backgroundDark2", color="r")
+    pl.style.use("default")
+
+
+@image_comparison(
+    baseline_images=["backgroundSolarized"],
+    remove_text=True,
+    extensions=["png"],
+)
+def test_backgroundSolarized():
+    pl.style.use("Solarize_Light2")
+    _run_hist2d("backgroundSolarized")
+    pl.style.use("default")
+
+
+@image_comparison(
+    baseline_images=["backgroundSeaborn"], remove_text=True, extensions=["png"]
+)
+def test_backgroundSeaborn():
+    pl.style.use("seaborn")
+    _run_hist2d("backgroundSeaborn")
+    pl.style.use("default")
+
+
+@image_comparison(
+    baseline_images=["backgroundColor"], remove_text=True, extensions=["png"]
+)
+def test_backgroundColor():
+    pl.style.use("default")
+    matplotlib.rcParams["axes.facecolor"] = "yellow"
+    matplotlib.rcParams["axes.edgecolor"] = "red"
+    matplotlib.rcParams["xtick.color"] = "green"
+    matplotlib.rcParams["ytick.color"] = "blue"
+    _run_hist2d("backgroundColor")
+    pl.style.use("default")
+
+
 @image_comparison(
     baseline_images=["levels1"], remove_text=True, extensions=["png"]
 )