Fix image bbox clip.

The baseline image change was due to previously off-by-one clipping, as
can be checked by additionally drawing a line with the same clipbox and
checking that the image was clipped one pixel row/column too far:

    from matplotlib import pyplot as plt, patches

    fig, ax = plt.subplots()
    d = [[1, 2], [3, 4]]

    im = ax.imshow(d, extent=(0, 5, 0, 5), cmap="viridis")
    l, = ax.plot([0, 5], [0, 5])

    rect = patches.Rectangle(
        xy=(1, 1), width=2, height=2, transform=im.axes.transData)
    im.set_clip_path(rect)
    l.set_clip_path(rect)

    plt.show()

Author: anntzer

lib/matplotlib/image.py

@@ -863,8 +863,9 @@ def make_image(self, renderer, magnification=1.0, unsampled=False):
         bbox = Bbox(np.array([[x1, y1], [x2, y2]]))
         transformed_bbox = TransformedBbox(bbox, trans)
         return self._make_image(
-            self._A, bbox, transformed_bbox, self.axes.bbox, magnification,
-            unsampled=unsampled)
+            self._A, bbox, transformed_bbox,
+            self.get_clip_box() or self.axes.bbox,
+            magnification, unsampled=unsampled)
 
     def _check_unsampled_image(self, renderer):
         """

lib/matplotlib/tests/baseline_images/test_image/image_cliprect.png

@@ -1083,3 +1083,21 @@ def test_deprecation():
         with pytest.warns(MatplotlibDeprecationWarning):
             # Enough arguments to pass "shape" positionally.
             obj.imshow(data, *[None] * 10)
+
+
+def test_respects_bbox():
+    fig, axs = plt.subplots(2)
+    for ax in axs:
+        ax.set_axis_off()
+    im = axs[1].imshow([[0, 1], [2, 3]], aspect="auto", extent=(0, 1, 0, 1))
+    im.set_clip_path(None)
+    # Make the image invisible in axs[1], but visible in axs[0] if we pan
+    # axs[1] up.
+    im.set_clip_box(axs[0].bbox)
+    buf_before = io.BytesIO()
+    fig.savefig(buf_before, format="rgba")
+    assert {*buf_before.getvalue()} == {0xff}  # All white.
+    axs[1].set(ylim=(-1, 0))
+    buf_after = io.BytesIO()
+    fig.savefig(buf_after, format="rgba")
+    assert buf_before.getvalue() != buf_after.getvalue()  # Not all white.