Merge pull request matplotlib#27640 from dstansby/non-uniform-z

Add `get_cursor_data` to `NonUniformImage`

Author: QuLogic

doc/users/next_whats_new/nonuniformimage_mousover.rst

@@ -0,0 +1,4 @@
+NonUniformImage now has mouseover support
+-----------------------------------------
+When mousing over a `~matplotlib.image.NonUniformImage` the data values are now
+displayed.

lib/matplotlib/image.py

@@ -1038,7 +1038,6 @@ def get_cursor_data(self, event):
 
 
 class NonUniformImage(AxesImage):
-    mouseover = False  # This class still needs its own get_cursor_data impl.
 
     def __init__(self, ax, *, interpolation='nearest', **kwargs):
         """
@@ -1190,6 +1189,16 @@ def set_cmap(self, cmap):
             raise RuntimeError('Cannot change colors after loading data')
         super().set_cmap(cmap)
 
+    def get_cursor_data(self, event):
+        # docstring inherited
+        x, y = event.xdata, event.ydata
+        if (x < self._Ax[0] or x > self._Ax[-1] or
+                y < self._Ay[0] or y > self._Ay[-1]):
+            return None
+        j = np.searchsorted(self._Ax, x) - 1
+        i = np.searchsorted(self._Ay, y) - 1
+        return self._A[i, j]
+
 
 class PcolorImage(AxesImage):
     """
@@ -1322,10 +1331,7 @@ def get_cursor_data(self, event):
             return None
         j = np.searchsorted(self._Ax, x) - 1
         i = np.searchsorted(self._Ay, y) - 1
-        try:
-            return self._A[i, j]
-        except IndexError:
-            return None
+        return self._A[i, j]
 
 
 class FigureImage(_ImageBase):

lib/matplotlib/tests/test_image.py

@@ -365,6 +365,38 @@ def test_cursor_data():
     assert im.get_cursor_data(event) == 44
 
 
+@pytest.mark.parametrize("xy, data", [
+    # x/y coords chosen to be 0.5 above boundaries so they lie within image pixels
+    [[0.5, 0.5], 0 + 0],
+    [[0.5, 1.5], 0 + 1],
+    [[4.5, 0.5], 16 + 0],
+    [[8.5, 0.5], 16 + 0],
+    [[9.5, 2.5], 81 + 4],
+    [[-1, 0.5], None],
+    [[0.5, -1], None],
+    ]
+)
+def test_cursor_data_nonuniform(xy, data):
+    from matplotlib.backend_bases import MouseEvent
+
+    # Non-linear set of x-values
+    x = np.array([0, 1, 4, 9, 16])
+    y = np.array([0, 1, 2, 3, 4])
+    z = x[np.newaxis, :]**2 + y[:, np.newaxis]**2
+
+    fig, ax = plt.subplots()
+    im = NonUniformImage(ax, extent=(x.min(), x.max(), y.min(), y.max()))
+    im.set_data(x, y, z)
+    ax.add_image(im)
+    # Set lower min lim so we can test cursor outside image
+    ax.set_xlim(x.min() - 2, x.max())
+    ax.set_ylim(y.min() - 2, y.max())
+
+    xdisp, ydisp = ax.transData.transform(xy)
+    event = MouseEvent('motion_notify_event', fig.canvas, xdisp, ydisp)
+    assert im.get_cursor_data(event) == data, (im.get_cursor_data(event), data)
+
+
 @pytest.mark.parametrize(
     "data, text", [
         ([[10001, 10000]], "[10001.000]"),