From 3a1c196401915a63733c45d1916af3656b7a71ee Mon Sep 17 00:00:00 2001
From: Illviljan <14371165+Illviljan@users.noreply.github.com>
Date: Wed, 16 Jun 2021 18:19:20 +0200
Subject: [PATCH] Don't handle pixel centering when inputs are strings.

Has to be refixed if/when ax.imshow allows categorical data.
---
 xarray/plot/plot.py | 29 ++++++++++++-----------------
 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/xarray/plot/plot.py b/xarray/plot/plot.py
index 37e9a1c40d9..e4926395f84 100644
--- a/xarray/plot/plot.py
+++ b/xarray/plot/plot.py
@@ -927,23 +927,18 @@ def imshow(x, y, z, ax, **kwargs):
             "imshow requires 1D coordinates, try using pcolormesh or contour(f)"
         )
 
-    def _maybe_center_pixels(x):
-        """Center the pixels on the coordinates."""
-        if np.issubdtype(x.dtype, str):
-            # Categorical data cannot be centered:
-            return None, None
-
-        try:
-            # Center the pixels assuming uniform spacing:
-            xstep = 0.5 * (x[1] - x[0])
-        except IndexError:
-            # Arbitrary default value, similar to matplotlib behaviour:
-            xstep = 0.1
-        return x[0] - xstep, x[-1] + xstep
-
-    # Try to center the pixels:
-    left, right = _maybe_center_pixels(x)
-    top, bottom = _maybe_center_pixels(y)
+    # Centering the pixels- Assumes uniform spacing
+    try:
+        xstep = (x[1] - x[0]) / 2.0
+    except IndexError:
+        # Arbitrary default value, similar to matplotlib behaviour
+        xstep = 0.1
+    try:
+        ystep = (y[1] - y[0]) / 2.0
+    except IndexError:
+        ystep = 0.1
+    left, right = x[0] - xstep, x[-1] + xstep
+    bottom, top = y[-1] + ystep, y[0] - ystep
 
     defaults = {"origin": "upper", "interpolation": "nearest"}