Update scalebar.py (#40)

* Update scalebar.py

Formalizes the changes suggested by altanir84 in #39 to add support for bbox_to_anchor
Additionally implements get_window_extent

* Update scalebar.py

* Update scalebar.py

* Update scalebar.py

* Apply linter

* Fix use of bbox and add example

* Add doc in README. Add unit test

* Add contributor

---------

Co-authored-by: Philippe Pinard <philippe.pinard@gmail.com>

README.md

@@ -118,6 +118,8 @@ scalebar = ScaleBar(
         fixed_units=None,
         animated=False,
         rotation=None,
+        bbox_to_anchor=None,
+        bbox_transform=None,
     )
 ```
 
@@ -333,12 +335,50 @@ ax.add_artist(scalebar)
 
 ![rotation](doc/argument_rotation.png)
 
+### bbox_to_anchor and bbox_transform
+
+Use a different bounding box than the plot axes to anchor the scale bar.
+The *bbox_transform* defines the transform applied to the *bbox_to_anchor* value.
+Note that the *location* will influence the position of the scale bar relative to the anchor (see example below).
+Default: `None`, the plot axes bounding box is used.
+
+```python
+fig, ax = plt.subplots()
+
+scalebar = ScaleBar(
+    1,
+    "cm",
+    length_fraction=0.25,
+    bbox_to_anchor=(0.5, 0.5),
+    bbox_transform=ax.transAxes,
+    location="lower left",
+    label="lower left",
+    box_color="0.8",
+)
+ax.add_artist(scalebar)
+
+scalebar = ScaleBar(
+    1,
+    "cm",
+    length_fraction=0.25,
+    bbox_to_anchor=(0.5, 0.5),
+    bbox_transform=ax.transAxes,
+    location="upper right",
+    label="upper right",
+    box_color="0.8",
+)
+ax.add_artist(scalebar)
+```
+
+![rotation](doc/argument_bbox_to_anchor.png)
+
 ## Release notes
 
 ### Dev
 
 * Update tooling ([#53][i53])
 * Add example gallery ([#50][i50])
+* Add *bbox_anchor* and *bbox_transform* ([#40](i40))
 
 ### 0.8.1
 
@@ -422,13 +462,14 @@ ax.add_artist(scalebar)
 [@anntzer](https://github.com/anntzer),
 [@bugalo](https://github.com/bugalo),
 [@musicinmybrain](https://github.com/musicinmybrain),
-[@kolibril13](https://github.com/kolibril13)
+[@kolibril13](https://github.com/kolibril13),
+[@ilopata1](https://github.com/ilopata1)
 
 ## License
 
 License under the BSD License, compatible with matplotlib.
 
-Copyright (c) 2015-2022 Philippe Pinard
+Copyright (c) 2015-2023 Philippe Pinard
 
 [i9]: https://github.com/ppinard/matplotlib-scalebar/issues/9
 [i11]: https://github.com/ppinard/matplotlib-scalebar/issues/11
@@ -448,6 +489,7 @@ Copyright (c) 2015-2022 Philippe Pinard
 [i35]: https://github.com/ppinard/matplotlib-scalebar/issues/35
 [i36]: https://github.com/ppinard/matplotlib-scalebar/issues/36
 [i41]: https://github.com/ppinard/matplotlib-scalebar/issues/41
+[i40]: https://github.com/ppinard/matplotlib-scalebar/pull/40
 [i44]: https://github.com/ppinard/matplotlib-scalebar/pull/44
 [i47]: https://github.com/ppinard/matplotlib-scalebar/pull/47
 [i48]: https://github.com/ppinard/matplotlib-scalebar/pull/48

doc/argument_bbox_to_anchor.py

@@ -0,0 +1,32 @@
+from pathlib import Path
+import matplotlib.pyplot as plt
+from matplotlib_scalebar.scalebar import ScaleBar
+
+fig, ax = plt.subplots()
+
+scalebar = ScaleBar(
+    1,
+    "cm",
+    length_fraction=0.25,
+    bbox_to_anchor=(0.5, 0.5),
+    bbox_transform=ax.transAxes,
+    location="lower left",
+    label="lower left",
+    box_color="0.8",
+)
+ax.add_artist(scalebar)
+
+scalebar = ScaleBar(
+    1,
+    "cm",
+    length_fraction=0.25,
+    bbox_to_anchor=(0.5, 0.5),
+    bbox_transform=ax.transAxes,
+    location="upper right",
+    label="upper right",
+    box_color="0.8",
+)
+ax.add_artist(scalebar)
+
+outdir = Path(__file__).parent.resolve()
+fig.savefig(outdir / "argument_bbox_to_anchor.png", dpi=60, bbox_inches="tight")

doc/splashscreen.py

@@ -12,7 +12,7 @@
 
 ax.imshow(im, "gray")
 
-# According to Wikipedia, 
+# According to Wikipedia,
 # "the bean shaped grain in the bottom left corner is about 50 μm long."
 scalebar = ScaleBar(
     50 / 144, "um", location="lower right", width_fraction=0.02, border_pad=1, pad=0.5

matplotlib_scalebar/scalebar.py

@@ -183,6 +183,8 @@ def __init__(
         fixed_units=None,
         animated=False,
         rotation=None,
+        bbox_to_anchor=None,
+        bbox_transform=None,
     ):
         """
         Creates a new scale bar.
@@ -299,6 +301,13 @@ def __init__(
         :arg rotation: either ``horizontal`` or ``vertical``
             (default: rcParams['scalebar.rotation'] or ``horizontal``)
         :type rotation: :class:`str`
+
+        :arg bbox_to_anchor: box that is used to position the scalebar
+            in conjunction with location. If ``None`` the figure bbox is used.
+        :type bbox_to_anchor: :class:`BboxBase`, `2-tuple`, or `4-tuple` of floats
+
+        :arg bbox_transform: transform for the bounding box
+        :type bbox_transform: :class:`matplotlib.transforms.Transform`
         """
         Artist.__init__(self)
 
@@ -346,6 +355,8 @@ def __init__(
         self.fixed_units = fixed_units
         self.set_animated(animated)
         self.rotation = rotation
+        self.bbox_to_anchor = bbox_to_anchor
+        self.bbox_transform = bbox_transform
 
     def _calculate_best_length(self, length_px):
         dx = self.dx
@@ -509,7 +520,13 @@ def _get_value(attr, default):
             child = scale_box
 
         box = AnchoredOffsetbox(
-            loc=location, pad=pad, borderpad=border_pad, child=child, frameon=frameon
+            loc=location,
+            pad=pad,
+            child=child,
+            borderpad=border_pad,
+            frameon=frameon,
+            bbox_to_anchor=self.bbox_to_anchor,
+            bbox_transform=self.bbox_transform,
         )
 
         box.axes = ax
@@ -788,3 +805,19 @@ def set_rotation(self, rotation):
         self._rotation = rotation
 
     rotation = property(get_rotation, set_rotation)
+
+    def get_bbox_to_anchor(self):
+        return self._bbox_to_anchor
+
+    def set_bbox_to_anchor(self, bbox_to_anchor):
+        self._bbox_to_anchor = bbox_to_anchor
+
+    bbox_to_anchor = property(get_bbox_to_anchor, set_bbox_to_anchor)
+
+    def get_bbox_transform(self):
+        return self._bbox_transform
+
+    def set_bbox_transform(self, bbox_transform):
+        self._bbox_transform = bbox_transform
+
+    bbox_transform = property(get_bbox_transform, set_bbox_transform)

matplotlib_scalebar/test_scalebar.py

@@ -19,6 +19,7 @@
 
 matplotlib.use("agg")
 
+
 @pytest.fixture
 def scalebar():
     fig = plt.figure()
@@ -308,3 +309,21 @@ def test_rotation(scalebar, rotation):
 
     with pytest.raises(ValueError):
         scalebar.set_rotation("h")
+
+
+def test_bbox_to_anchor(scalebar):
+    assert scalebar.get_bbox_to_anchor() is None
+    assert scalebar.bbox_to_anchor is None
+
+    scalebar.bbox_to_anchor = (0.5, 0.5)
+    assert scalebar.get_bbox_to_anchor() == (0.5, 0.5)
+    assert scalebar.bbox_to_anchor == (0.5, 0.5)
+
+
+def test_bbox_transform(scalebar):
+    assert scalebar.get_bbox_transform() is None
+    assert scalebar.bbox_transform is None
+
+    scalebar.bbox_transform = scalebar.axes.transAxes
+    assert scalebar.get_bbox_transform() == scalebar.axes.transAxes
+    assert scalebar.bbox_transform == scalebar.axes.transAxes