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Fix: support alpha array for RGB images in imshow (closes #26092) #30111

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Fix: support alpha array for RGB images in imshow (closes #26092) #30111

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9eaca48
ENH: Dynamically resize symbol tables (max 6 columns)
Vaishnavi-Raghupathi May 26, 2025
1f84150
ENH: Apply alpha array to RGB images in imshow (Fix #26092)
Vaishnavi-Raghupathi May 26, 2025
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33 changes: 17 additions & 16 deletions doc/sphinxext/math_symbol_table.py
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These changes do not belong in this PR.

Original file line number Diff line number Diff line change
Expand Up @@ -9,57 +9,57 @@

symbols = [
["Lower-case Greek",
4,
0,
(r"\alpha", r"\beta", r"\gamma", r"\chi", r"\delta", r"\epsilon",
r"\eta", r"\iota", r"\kappa", r"\lambda", r"\mu", r"\nu", r"\omega",
r"\phi", r"\pi", r"\psi", r"\rho", r"\sigma", r"\tau", r"\theta",
r"\upsilon", r"\xi", r"\zeta", r"\digamma", r"\varepsilon", r"\varkappa",
r"\varphi", r"\varpi", r"\varrho", r"\varsigma", r"\vartheta")],
["Upper-case Greek",
4,
0,
(r"\Delta", r"\Gamma", r"\Lambda", r"\Omega", r"\Phi", r"\Pi", r"\Psi",
r"\Sigma", r"\Theta", r"\Upsilon", r"\Xi")],
["Hebrew",
6,
0,
(r"\aleph", r"\beth", r"\gimel", r"\daleth")],
["Latin named characters",
6,
0,
r"""\aa \AA \ae \AE \oe \OE \O \o \thorn \Thorn \ss \eth \dh \DH""".split()],
["Delimiters",
5,
0,
_mathtext.Parser._delims],
["Big symbols",
5,
0,
_mathtext.Parser._overunder_symbols | _mathtext.Parser._dropsub_symbols],
["Standard function names",
5,
0,
{fr"\{fn}" for fn in _mathtext.Parser._function_names}],
["Binary operation symbols",
4,
0,
_mathtext.Parser._binary_operators],
["Relation symbols",
4,
0,
_mathtext.Parser._relation_symbols],
["Arrow symbols",
4,
0,
_mathtext.Parser._arrow_symbols],
["Dot symbols",
4,
0,
r"""\cdots \vdots \ldots \ddots \adots \Colon \therefore \because""".split()],
["Black-board characters",
6,
0,
[fr"\{symbol}" for symbol in _mathtext_data.tex2uni
if re.match(bb_pattern, symbol)]],
["Script characters",
6,
0,
[fr"\{symbol}" for symbol in _mathtext_data.tex2uni
if re.match(scr_pattern, symbol)]],
["Fraktur characters",
6,
0,
[fr"\{symbol}" for symbol in _mathtext_data.tex2uni
if re.match(frak_pattern, symbol)]],
["Miscellaneous symbols",
4,
0,
r"""\neg \infty \forall \wp \exists \bigstar \angle \partial
\nexists \measuredangle \emptyset \sphericalangle \clubsuit
\varnothing \complement \diamondsuit \imath \Finv \triangledown
Expand Down Expand Up @@ -94,7 +94,8 @@ def render_symbol(sym, ignore_variant=False):
sym.startswith(r"\var")),
reverse=(category == "Hebrew")) # Hebrew is rtl
rendered_syms = [f"{render_symbol(sym)} ``{sym}``" for sym in syms]
columns = min(columns, len(syms))
max_columns = 6 # You can adjust this (e.g., 4–8)
columns = min(max_columns, len(syms)) # New dynamic logic
lines.append("**%s**" % category)
lines.append('')
max_width = max(map(len, rendered_syms))
Expand Down
9 changes: 6 additions & 3 deletions lib/matplotlib/image.py
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Original file line number Diff line number Diff line change
Expand Up @@ -511,14 +511,17 @@
if alpha is None: # alpha parameter not specified
if A.shape[2] == 3: # image has no alpha channel
A = np.dstack([A, np.ones(A.shape[:2])])
elif np.ndim(alpha) > 0: # Array alpha
elif np.ndim(alpha) > 0: # Array alpha

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Insert at least two spaces before an inline comment

Raw Output:
message:"Insert at least two spaces before an inline comment" location:{path:"/home/runner/work/matplotlib/matplotlib/lib/matplotlib/image.py" range:{start:{line:514 column:41} end:{line:514 column:42}}} source:{name:"ruff" url:"https://docs.astral.sh/ruff"} code:{value:"E261" url:"https://docs.astral.sh/ruff/rules/too-few-spaces-before-inline-comment"} suggestions:{range:{start:{line:514 column:41} end:{line:514 column:42}} text:"  "}
if alpha.shape != A.shape[:2]:
raise ValueError("Alpha array shape must match image dimensions")

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Line too long (95 > 88)

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message:"Line too long (95 > 88)" location:{path:"/home/runner/work/matplotlib/matplotlib/lib/matplotlib/image.py" range:{start:{line:516 column:89} end:{line:516 column:96}}} 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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Trailing whitespace

Raw Output:
message:"Trailing whitespace" location:{path:"/home/runner/work/matplotlib/matplotlib/lib/matplotlib/image.py" range:{start:{line:516 column:90} end:{line:516 column:96}}} 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:516 column:90} end:{line:516 column:96}}}

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lib/matplotlib/image.py#L516 

Added line #L516 was not covered by tests
# user-specified array alpha overrides the existing alpha channel
A = np.dstack([A[..., :3], alpha])
else: # Scalar alpha
if A.shape[2] == 3: # broadcast scalar alpha
A = np.dstack([A, np.full(A.shape[:2], alpha, np.float32)])
else: # or apply scalar alpha to existing alpha channel
post_apply_alpha = True
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Why is this removed?

#to handle RGBA inputs
if A.shape[2] == 4 and alpha is not None:
A[..., 3] = alpha # override existing alpha channel

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Trailing whitespace

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message:"Trailing whitespace" location:{path:"/home/runner/work/matplotlib/matplotlib/lib/matplotlib/image.py" range:{start:{line:524 column:73} end:{line:524 column:85}}} 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:524 column:73} end:{line:524 column:85}}}
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I think this is just repeating what already happened on line 518.

# Resample in premultiplied alpha space. (TODO: Consider
# implementing premultiplied-space resampling in
# span_image_resample_rgba_affine::generate?)
Expand Down
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