Fix boxplot conversion by mapping 'none' colors to transparent rgba

CHANGELOG.md

@@ -10,6 +10,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - Fix `mpl_to_plotly` crashing on touching bars (such as `plt.hist`) due to floating-point noise producing negative `bargap` values by clamping `bargap` to `[0, 1]` [[#5696](https://github.com/plotly/plotly.py/pull/5696)], with thanks to @robertoffmoura for the contribution!
 - Fix `mpl_to_plotly` drawing step plots with diagonal lines instead of vertical/horizontal step segments by mapping matplotlib step drawstyles (`steps-pre`, `steps-post`, `steps-mid`) to plotly line shapes [[#5697](https://github.com/plotly/plotly.py/pull/5697)], with thanks to @robertoffmoura for the contribution!
 - Fix `mpl_to_plotly` showing unwanted legends with placeholder or internal label entries (`_nolegend_`, `_childN`) by defaulting `layout.showlegend=False` unless the matplotlib figure explicitly defines a legend [[#5699](https://github.com/plotly/plotly.py/pull/5699)], with thanks to @robertoffmoura for the contribution!
+- Fix `mpl_to_plotly` crashing on figures with fully transparent or alpha-carrying colors, such as boxplot outlier markers (`facecolor="none"`), rgba line colors, and `color="none"` text and axis labels; all matplotlib colors are now exported through a single helper that maps `"none"` to transparent rgba and keeps or overrides alpha as matplotlib does [[#5700](https://github.com/plotly/plotly.py/pull/5700)], with thanks to @robertoffmoura for the contribution!
 - Export tick label colors to the plotly tickfont in `mpl_to_plotly` [[#5716](https://github.com/plotly/plotly.py/pull/5716)], with thanks to @robertoffmoura for the contribution!
 - Fix `px.sunburst`, `px.treemap` and `px.icicle` listing sectors in a different order on every run when `path` is used with a Polars DataFrame; sectors now follow their order of first appearance for all dataframe backends [[#5766](https://github.com/plotly/plotly.py/pull/5766)], with thanks to @Irahan2 for the contribution!
 

plotly/matplotlylib/mpltools.py

@@ -12,6 +12,8 @@
 
 from _plotly_utils.colors import hex_to_rgb
 
+from plotly.matplotlylib.mplexporter.utils import export_color
+
 
 def check_bar_match(old_bar, new_bar):
     """Check if two bars belong in the same collection (bar chart).
@@ -106,26 +108,6 @@ def convert_symbol(mpl_symbol):
         return "circle"  # default
 
 
-def merge_color_and_opacity(color, opacity):
-    """
-    Merge hex color with an alpha (opacity) to get an rgba tuple.
-
-    :param (str|unicode) color: A hex color string.
-    :param (float|int) opacity: A value [0, 1] for the 'a' in 'rgba'.
-    :return: (int, int, int, float) The rgba color and alpha tuple.
-
-    """
-    if color is None:  # None can be used as a placeholder, just bail.
-        return None
-
-    rgb_tup = hex_to_rgb(color)
-    if opacity is None:
-        return "rgb{}".format(rgb_tup)
-
-    rgba_tup = rgb_tup + (opacity,)
-    return "rgba{}".format(rgba_tup)
-
-
 def convert_va(mpl_va):
     """Convert mpl vertical alignment word to equivalent HTML word.
 
@@ -530,19 +512,29 @@ def prep_ticks(ax, index, ax_type, props):
     return axis_dict
 
 
-def _export_color(color):
+def _export_color(color, opacity=None):
     """Export a matplotlib color for use as a plotly color.
 
     matplotlib uses "none" for fully transparent colors, which plotly does not
-    accept, so transparent colors are exported as transparent black.
-    Colors already exported by the mplexporter (hex or rgba strings) are
-    passed through unchanged.
+    accept, so transparent colors are exported as transparent black. Colors
+    already exported by the mplexporter (hex or rgba strings) keep the alpha
+    they carry unless an explicit opacity overrides it.
     """
     if color is None:
         return None
-    if isinstance(color, str):
-        return color if color != "none" else "rgba(0,0,0,0)"
-    return [_export_color(c) for c in color]
+    if isinstance(color, (list, tuple)) and all(isinstance(c, str) for c in color):
+        return [_export_color(c, opacity) for c in color]
+    if not isinstance(color, str):
+        color = export_color(color)
+    if color == "none":
+        return "rgba(0,0,0,0)"
+    if color.startswith("#") and opacity is not None:
+        return "rgba{0}".format(hex_to_rgb(color) + (opacity,))
+    if color.startswith("rgb") and opacity not in (None, 1):
+        rgb = color[color.index("(") + 1 : color.rindex(")")].split(",")
+        r, g, b = (int(round(float(component))) for component in rgb[:3])
+        return "rgba({0}, {1}, {2}, {3})".format(r, g, b, opacity)
+    return color
 
 
 def prep_xy_axis(ax, props, x_bounds, y_bounds):

plotly/matplotlylib/renderer.py

@@ -384,7 +384,7 @@ def draw_bar(self, coll):
             yaxis="y{0}".format(self.axis_ct),
             opacity=trace[0]["alpha"],  # TODO: get all alphas if array?
             marker=go.bar.Marker(
-                color=trace[0]["facecolor"],  # TODO: get all
+                color=_export_color(trace[0]["facecolor"]),  # TODO: get all
                 line=dict(width=trace[0]["edgewidth"]),
             ),
         )  # TODO ditto
@@ -446,7 +446,7 @@ def draw_marked_line(self, **props):
             self.msg += "... with just markers\n"
             mode = "markers"
         if props["linestyle"]:
-            color = mpltools.merge_color_and_opacity(
+            color = _export_color(
                 props["linestyle"]["color"], props["linestyle"]["alpha"]
             )
 
@@ -469,22 +469,22 @@ def draw_marked_line(self, **props):
             if props["coordinates"] == "data":
                 marker = go.scatter.Marker(
                     opacity=props["markerstyle"]["alpha"],
-                    color=props["markerstyle"]["facecolor"],
+                    color=_export_color(props["markerstyle"]["facecolor"]),
                     symbol=mpltools.convert_symbol(props["markerstyle"]["marker"]),
                     size=props["markerstyle"]["markersize"],
                     line=dict(
-                        color=props["markerstyle"]["edgecolor"],
+                        color=_export_color(props["markerstyle"]["edgecolor"]),
                         width=props["markerstyle"]["edgewidth"],
                     ),
                 )
             else:
                 shape = dict(
                     opacity=props["markerstyle"]["alpha"],
-                    fillcolor=props["markerstyle"]["facecolor"],
+                    fillcolor=_export_color(props["markerstyle"]["facecolor"]),
                     symbol=mpltools.convert_symbol(props["markerstyle"]["marker"]),
                     size=props["markerstyle"]["markersize"],
                     line=dict(
-                        color=props["markerstyle"]["edgecolor"],
+                        color=_export_color(props["markerstyle"]["edgecolor"]),
                         width=props["markerstyle"]["edgewidth"],
                     ),
                 )
@@ -782,7 +782,8 @@ def draw_text(self, **props):
                 yanchor=yanchor,
                 showarrow=False,  # change this later?
                 font=go.layout.annotation.Font(
-                    color=props["style"]["color"], size=props["style"]["fontsize"]
+                    color=_export_color(props["style"]["color"]),
+                    size=props["style"]["fontsize"],
                 ),
             )
             self.plotly_fig["layout"]["annotations"] += (annotation,)
@@ -822,7 +823,8 @@ def draw_title(self, **props):
             annotation = go.layout.Annotation(
                 text=props["text"],
                 font=go.layout.annotation.Font(
-                    color=props["style"]["color"], size=props["style"]["fontsize"]
+                    color=_export_color(props["style"]["color"]),
+                    size=props["style"]["fontsize"],
                 ),
                 xref="paper",
                 yref="paper",
@@ -837,7 +839,8 @@ def draw_title(self, **props):
             self.msg += "          Only one subplot found, adding as a plotly title\n"
             self.plotly_fig["layout"]["title"] = props["text"]
             title_font = dict(
-                size=props["style"]["fontsize"], color=props["style"]["color"]
+                size=props["style"]["fontsize"],
+                color=_export_color(props["style"]["color"]),
             )
             self.plotly_fig["layout"]["title_font"] = title_font
 
@@ -868,7 +871,8 @@ def draw_xlabel(self, **props):
         axis_key = "xaxis{0}".format(self.axis_ct)
         self.plotly_fig["layout"][axis_key]["title"] = str(props["text"])
         title_font = dict(
-            size=props["style"]["fontsize"], color=props["style"]["color"]
+            size=props["style"]["fontsize"],
+            color=_export_color(props["style"]["color"]),
         )
         self.plotly_fig["layout"][axis_key]["title_font"] = title_font
 
@@ -899,7 +903,8 @@ def draw_ylabel(self, **props):
         axis_key = "yaxis{0}".format(self.axis_ct)
         self.plotly_fig["layout"][axis_key]["title"] = props["text"]
         title_font = dict(
-            size=props["style"]["fontsize"], color=props["style"]["color"]
+            size=props["style"]["fontsize"],
+            color=_export_color(props["style"]["color"]),
         )
         self.plotly_fig["layout"][axis_key]["title_font"] = title_font
 

plotly/matplotlylib/tests/test_renderer.py

@@ -322,6 +322,113 @@ def test_pcolor_rectangles_render():
     assert all(len(t.x) >= 4 for t in plotly_fig.data)
 
 
+def test_boxplot_converts_with_none_marker_facecolor():
+    """Boxplot outlier markers use facecolor 'none', which plotly rejects."""
+    fig, ax = plt.subplots()
+    ax.boxplot(np.random.randn(100, 4))
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert len(plotly_fig.data) > 0
+
+
+def test_line_with_none_color_converts():
+    """Lines with color='none' use the string 'none' for the line color,
+    which plotly rejects; it must be exported as a transparent line."""
+    fig, ax = plt.subplots()
+    ax.plot([0, 1], [0, 1], color="none")
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert len(plotly_fig.data) == 1
+    assert plotly_fig.data[0].line.color == "rgba(0,0,0,0)"
+
+
+def test_line_with_rgba_color_converts():
+    """Line colors that carry their own alpha (rgba tuple or 8-digit hex)
+    export as rgba strings."""
+    fig, ax = plt.subplots()
+    ax.plot([0, 1], [0, 1], color=(1.0, 0.0, 0.0, 0.5))
+    ax.plot([0, 1], [1, 0], color="#0000FF80")
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert plotly_fig.data[0].line.color == "rgba(255, 0, 0, 0.5)"
+    assert plotly_fig.data[1].line.color == "rgba(0, 0, 255, 0.5019607843137255)"
+
+
+def test_line_rgba_color_with_separate_alpha_converts():
+    """An explicit alpha overrides the alpha carried by the line color."""
+    fig, ax = plt.subplots()
+    ax.plot([0, 1], [0, 1], color=(1.0, 0.0, 0.0, 0.2), alpha=0.5)
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert plotly_fig.data[0].line.color == "rgba(255, 0, 0, 0.5)"
+
+
+def test_transparent_text_colors_export():
+    """Text, title, and axis labels with color 'none' export transparent
+    fonts."""
+    fig, ax = plt.subplots()
+    ax.text(0.5, 0.5, "text", color="none")
+    ax.set_title("title", color="none")
+    ax.set_xlabel("xlabel", color="none")
+    ax.set_ylabel("ylabel", color="none")
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert plotly_fig.layout.annotations[0].font.color == "rgba(0,0,0,0)"
+    assert plotly_fig.layout.title.font.color == "rgba(0,0,0,0)"
+    assert plotly_fig.layout.xaxis.title.font.color == "rgba(0,0,0,0)"
+    assert plotly_fig.layout.yaxis.title.font.color == "rgba(0,0,0,0)"
+
+
+def test_export_color_maps_colors():
+    """_export_color maps matplotlib color strings to plotly colors, keeping
+    or overriding the alpha as requested."""
+    from plotly.matplotlylib.mpltools import _export_color
+
+    expected_mappings = {
+        (None, None): None,
+        ("none", None): "rgba(0,0,0,0)",
+        ("#FF0000", None): "#FF0000",
+        ("#FF0000", 1): "rgba(255, 0, 0, 1)",
+        ("#FF0000", 0.5): "rgba(255, 0, 0, 0.5)",
+        ("rgba(255, 0, 0, 0.2)", None): "rgba(255, 0, 0, 0.2)",
+        ("rgba(255, 0, 0, 0.2)", 1): "rgba(255, 0, 0, 0.2)",
+        ("rgba(255, 0, 0, 0.2)", 0.5): "rgba(255, 0, 0, 0.5)",
+        ("rgb(255, 0, 0)", None): "rgb(255, 0, 0)",
+        ("rgb(255, 0, 0)", 0.5): "rgba(255, 0, 0, 0.5)",
+        ((1.0, 0.0, 0.0, 0.5), None): "rgba(255, 0, 0, 0.5)",
+        ((0.0, 1.0, 0.0, 1.0), None): "#00FF00",
+    }
+    for (color, opacity), expected in expected_mappings.items():
+        result = _export_color(color, opacity)
+        assert result == expected, (
+            f"Input {color!r} with opacity {opacity!r} produced {result!r}, "
+            f"expected {expected!r}"
+        )
+
+    assert _export_color(["#FF0000", "none"]) == ["#FF0000", "rgba(0,0,0,0)"]
+    assert _export_color(["rgba(255, 0, 0, 0.2)"], 0.5) == ["rgba(255, 0, 0, 0.5)"]
+
+
+def test_scatter_with_multiple_colors_converts():
+    """Scatter markers with per-point colors export a list of marker colors."""
+    fig, ax = plt.subplots()
+    ax.scatter([0, 1, 2], [0, 1, 2], c=["red", "green", "blue"])
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert plotly_fig.data[0].mode == "markers"
+    assert plotly_fig.data[0].marker.color == (
+        "rgba(255,0,0,1.0)",
+        "rgba(0,128,0,1.0)",
+        "rgba(0,0,255,1.0)",
+    )
+
+
 def test_eventplot_segments_render():
     fig, ax = plt.subplots()
     ax.eventplot([np.random.randn(20) for _ in range(5)])