breakup annotationbbox demo and add annotationbbox to annotation guide

matplotlib · Dec 23, 2024 · 04e428f · 04e428f
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diff --git a/galleries/examples/text_labels_and_annotations/demo_annotation_box.py b/galleries/examples/text_labels_and_annotations/demo_annotation_box.py
@@ -1,12 +1,12 @@
 """
-===================
-AnnotationBbox demo
-===================
-
-`.AnnotationBbox` creates an annotation using an `.OffsetBox`, and
-provides more fine-grained control than `.Axes.annotate`.  This example
-demonstrates the use of AnnotationBbox together with three different
-OffsetBoxes: `.TextArea`, `.DrawingArea`, and `.OffsetImage`.
+======================
+Artists as annotations
+======================
+
+`.AnnotationBbox` creates an annotation using an `.OffsetBox` object, which is a class
+of container artists for positioning an artist relative to a parent artist. This allows
+for annotations that are texts, images, and arbitrary artists.  `.AnnotationBbox` also
+provides more fine-grained control than `.Axes.annotate`.
 """
 
 import matplotlib.pyplot as plt
@@ -15,8 +15,16 @@
 from matplotlib.cbook import get_sample_data
 from matplotlib.offsetbox import (AnnotationBbox, DrawingArea, OffsetImage,
                                   TextArea)
-from matplotlib.patches import Circle
+from matplotlib.patches import Annulus, Circle
 
+# %%%%
+# Text
+# ====
+#
+# `.AnnotationBbox` supports positioning annotations relative to data, Artists, and
+# callables, as described in :ref:`annotations`. The  `.TextArea` is used to create a
+# textbox that is not explicitly attached to an axes.
+#
 fig, ax = plt.subplots()
 
 # Define a 1st position to annotate (display it with a marker)
@@ -26,46 +34,37 @@
 # Annotate the 1st position with a text box ('Test 1')
 offsetbox = TextArea("Test 1")
 
-ab = AnnotationBbox(offsetbox, xy,
-                    xybox=(-20, 40),
-                    xycoords='data',
-                    boxcoords="offset points",
-                    arrowprops=dict(arrowstyle="->"),
-                    bboxprops=dict(boxstyle="sawtooth"))
-ax.add_artist(ab)
+ab1 = AnnotationBbox(offsetbox, xy,
+                     xybox=(-20, 40),
+                     xycoords='data',
+                     boxcoords="offset points",
+                     arrowprops=dict(arrowstyle="->"),
+                     bboxprops=dict(boxstyle="sawtooth"))
+ax.add_artist(ab1)
 
 # Annotate the 1st position with another text box ('Test')
-offsetbox = TextArea("Test")
-
-ab = AnnotationBbox(offsetbox, xy,
-                    xybox=(1.02, xy[1]),
-                    xycoords='data',
-                    boxcoords=("axes fraction", "data"),
-                    box_alignment=(0., 0.5),
-                    arrowprops=dict(arrowstyle="->"))
-ax.add_artist(ab)
+offsetbox = TextArea("Test 2")
 
-# Define a 2nd position to annotate (don't display with a marker this time)
-xy = [0.3, 0.55]
+ab2 = AnnotationBbox(offsetbox, (1, .85),
+                     xybox=(.75, xy[1]),
+                     xycoords=ab1,
+                     boxcoords=("axes fraction", "data"),
+                     box_alignment=(0., 0.5),
+                     arrowprops=dict(arrowstyle="->"))
+ax.add_artist(ab2)
 
-# Annotate the 2nd position with a circle patch
-da = DrawingArea(20, 20, 0, 0)
-p = Circle((10, 10), 10)
-da.add_artist(p)
+# %%%%
+# Images
+# ======
+# The `.OffsetImage` container supports plotting images using `.BboxImage`
 
-ab = AnnotationBbox(da, xy,
-                    xybox=(1., xy[1]),
-                    xycoords='data',
-                    boxcoords=("axes fraction", "data"),
-                    box_alignment=(0.2, 0.5),
-                    arrowprops=dict(arrowstyle="->"),
-                    bboxprops=dict(alpha=0.5))
-
-ax.add_artist(ab)
+fig, ax = plt.subplots()
+# Define a position to annotate (don't display with a marker)
+xy = [0.3, 0.55]
 
-# Annotate the 2nd position with an image (a generated array of pixels)
+# Annotate a position with an image generated from an array of pixels
 arr = np.arange(100).reshape((10, 10))
-im = OffsetImage(arr, zoom=2)
+im = OffsetImage(arr, zoom=2, cmap='viridis')
 im.image.axes = ax
 
 ab = AnnotationBbox(im, xy,
@@ -74,10 +73,9 @@
                     boxcoords="offset points",
                     pad=0.3,
                     arrowprops=dict(arrowstyle="->"))
-
 ax.add_artist(ab)
 
-# Annotate the 2nd position with another image (a Grace Hopper portrait)
+# Annotate the position with another image (a Grace Hopper portrait)
 with get_sample_data("grace_hopper.jpg") as file:
     arr_img = plt.imread(file)
 
@@ -102,6 +100,36 @@
 
 plt.show()
 
+# %%%%
+# Arbitrary Artists
+# ================
+# `.DrawingArea` artists position arbitrary artists relative to their parent artists.
+
+fig, ax = plt.subplots()
+# Define a position to annotate (don't display with a marker)
+xy = [0.3, 0.55]
+
+# Annotate the position with a circle and annulus
+da = DrawingArea(30, 30, 0, 0)
+p = Circle((10, 10), 10, color='C0')
+da.add_artist(p)
+q = Annulus((20, 20), 10, 5, color='C1')
+da.add_artist(q)
+
+
+# Use the drawing area as an annotation
+ab = AnnotationBbox(da, xy,
+                    xybox=(.75, xy[1]),
+                    xycoords='data',
+                    boxcoords=("axes fraction", "data"),
+                    box_alignment=(0.2, 0.5),
+                    arrowprops=dict(arrowstyle="->"),
+                    bboxprops=dict(alpha=0.5))
+
+ax.add_artist(ab)
+plt.show()
+#
+
 # %%
 #
 # .. admonition:: References
@@ -117,3 +145,6 @@
 #    - `matplotlib.cbook.get_sample_data`
 #    - `matplotlib.pyplot.subplots`
 #    - `matplotlib.pyplot.imread`
+#
+# .. tags::
+#    component: annotation, styling: position
diff --git a/galleries/users_explain/text/annotations.py b/galleries/users_explain/text/annotations.py
@@ -691,11 +691,54 @@ def __call__(self, x0, y0, width, height, mutation_size):
 
 ax.add_artist(anchored_box)
 fig.subplots_adjust(top=0.8)
-
 # %%
 # Note that, unlike in `.Legend`, the ``bbox_transform`` is set to
 # `.IdentityTransform` by default
 #
+# .. _annotations-bbox:
+#
+# Using an Artist as an annotation
+# ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+# `.AnnotationBbox` uses `.OffsetBox` artists as the annotations and supports
+# positioning these annotations in the same was the other annotation methods.
+# For more examples, see
+# :doc:`/gallery/text_labels_and_annotations/demo_annotation_box`
+
+from matplotlib.offsetbox import AnnotationBbox, DrawingArea, OffsetImage
+from matplotlib.patches import Annulus
+
+fig, ax = plt.subplots()
+
+text = ax.text(.2, .8, "Green!", color='green')
+
+da = DrawingArea(20, 20, 0, 0)
+annulus = Annulus((10, 10), 10, 5, color='tab:green')
+da.add_artist(annulus)
+
+# position annulus relative to text
+ab1 = AnnotationBbox(da, (.5, 0),
+                     xybox=(.5, .25),
+                     xycoords=text,
+                     boxcoords=(text, "data"),
+                     arrowprops=dict(arrowstyle="->"),
+                     bboxprops=dict(alpha=0.5))
+ax.add_artist(ab1)
+
+N = 25
+arr = np.repeat(np.linspace(0, 10, N), N).reshape(N, N)
+im = OffsetImage(arr, cmap='Greens')
+im.image.axes = ax
+
+# position gradient relative to text and annulus
+ab2 = AnnotationBbox(im, xy=(.5, 0),
+                     xybox=(.75, 0),
+                     xycoords=text,
+                     boxcoords=('data', annulus),
+                     arrowprops=dict(arrowstyle="->"),
+                     bboxprops=dict(alpha=0.5))
+ax.add_artist(ab2)
+
+# %%%%
 # .. _annotating_coordinate_systems:
 #
 # Coordinate systems for annotations