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Fix imshow to support array alpha values and add corresponding test #30407

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Fix imshow to support array alpha values and add corresponding test #30407

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11 changes: 9 additions & 2 deletions lib/matplotlib/image.py
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Original file line number Diff line number Diff line change
Expand Up @@ -903,6 +903,10 @@
**kwargs
)

#support array value in imshow
if isinstance(self._alpha, np.ndarray):
self._set_alpha_for_array(self._alpha)

def get_window_extent(self, renderer=None):
x0, x1, y0, y1 = self._extent
bbox = Bbox.from_extents([x0, y0, x1, y1])
Expand Down Expand Up @@ -1579,8 +1583,10 @@

.. note::

If you want to save a single channel image as gray scale please use an
image I/O library (such as pillow, tifffile, or imageio) directly.
If *arr* is a single-channel (MxN) image and you want to save it as a grayscale image

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message:"Trailing whitespace" location:{path:"/home/runner/work/matplotlib/matplotlib/lib/matplotlib/image.py" range:{start:{line:1586 column:89} end:{line:1586 column:90}}} severity:WARNING source:{name:"ruff" url:"https://docs.astral.sh/ruff"} code:{value:"W291" url:"https://docs.astral.sh/ruff/rules/trailing-whitespace"} suggestions:{range:{start:{line:1586 column:89} end:{line:1586 column:90}}}

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message:"Line too long (89 > 88)" location:{path:"/home/runner/work/matplotlib/matplotlib/lib/matplotlib/image.py" range:{start:{line:1586 column:89} end:{line:1586 column:90}}} severity:WARNING source:{name:"ruff" url:"https://docs.astral.sh/ruff"} code:{value:"E501" url:"https://docs.astral.sh/ruff/rules/line-too-long"}

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message:"Docstring is under-indented" location:{path:"/home/runner/work/matplotlib/matplotlib/lib/matplotlib/image.py" range:{start:{line:1586 column:1} end:{line:1586 column:1}}} severity:WARNING source:{name:"ruff" url:"https://docs.astral.sh/ruff"} code:{value:"D207" url:"https://docs.astral.sh/ruff/rules/under-indentation"} suggestions:{range:{start:{line:1586 column:1} end:{line:1586 column:4}} text:"    "}
(instead of applying a colormap), consider using a dedicated image I/O library like

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message:"Trailing whitespace" location:{path:"/home/runner/work/matplotlib/matplotlib/lib/matplotlib/image.py" range:{start:{line:1587 column:87} end:{line:1587 column:88}}} severity:WARNING source:{name:"ruff" url:"https://docs.astral.sh/ruff"} code:{value:"W291" url:"https://docs.astral.sh/ruff/rules/trailing-whitespace"} suggestions:{range:{start:{line:1587 column:87} end:{line:1587 column:88}}}

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message:"Docstring is under-indented" location:{path:"/home/runner/work/matplotlib/matplotlib/lib/matplotlib/image.py" range:{start:{line:1587 column:1} end:{line:1587 column:1}}} severity:WARNING source:{name:"ruff" url:"https://docs.astral.sh/ruff"} code:{value:"D207" url:"https://docs.astral.sh/ruff/rules/under-indentation"} suggestions:{range:{start:{line:1587 column:1} end:{line:1587 column:4}} text:"    "}
Pillow, imageio, or tifffile. `imsave` will apply a colormap by default.

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message:"Docstring is under-indented" location:{path:"/home/runner/work/matplotlib/matplotlib/lib/matplotlib/image.py" range:{start:{line:1588 column:1} end:{line:1588 column:1}}} severity:WARNING source:{name:"ruff" url:"https://docs.astral.sh/ruff"} code:{value:"D207" url:"https://docs.astral.sh/ruff/rules/under-indentation"} suggestions:{range:{start:{line:1588 column:1} end:{line:1588 column:4}} text:"    "}


Parameters
----------
Expand Down Expand Up @@ -1658,6 +1664,7 @@
else:
sm = mcolorizer.Colorizer(cmap=cmap)
sm.set_clim(vmin, vmax)

rgba = sm.to_rgba(arr, bytes=True)
if pil_kwargs is None:
pil_kwargs = {}
Expand Down
11 changes: 11 additions & 0 deletions lib/matplotlib/tests/test_axes/test_imshow_alpha_array.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
import matplotlib.pyplot as plt
import numpy as np

def test_imshow_alpha_array():

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message:"Expected 2 blank lines, found 1" location:{path:"/home/runner/work/matplotlib/matplotlib/lib/matplotlib/tests/test_axes/test_imshow_alpha_array.py" range:{start:{line:4 column:1} end:{line:4 column:4}}} severity:WARNING source:{name:"ruff" url:"https://docs.astral.sh/ruff"} code:{value:"E302" url:"https://docs.astral.sh/ruff/rules/blank-lines-top-level"} suggestions:{range:{start:{line:3 column:1} end:{line:4 column:1}} text:"\n\n"}
data = np.random.rand(10, 10)
alpha = np.linspace(0, 1, 100).reshape(10, 10)

fig, ax = plt.subplots()
im = ax.imshow(data, alpha=alpha)
plt.colorbar(im, ax=ax)
return fig
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