Added hatch handling

Author: MadsAdrian

tikzplotlib/_hatches.py

@@ -0,0 +1,120 @@
+import warnings
+
+# From https://matplotlib.org/3.1.1/api/_as_gen/matplotlib.patches.Patch.html:
+# > Letters can be combined, in which case all the specified hatchings are done.
+# > If same letter repeats, it increases the density of hatching of that pattern.
+# To achieve something like this, custom patterns must be created
+# https://tex.stackexchange.com/questions/29359/pgfplots-how-to-fill-the-area-under-a-curve-with-oblique-lines-hatching-as-a/29367#29367
+
+# These methods exist, and might be relevant:
+# matplotlib.backend_bases.GraphicsContextBase.set/get_hatch_color
+# matplotlib.backend_bases.GraphicsContextBase.set/get_hatch_linewidth
+# hatch_density is mentioned in mpl API Changes in 2.0.1
+
+# for matplotlib hatches, see:
+# https://matplotlib.org/3.1.1/gallery/shapes_and_collections/hatch_demo.html
+
+# hatches in tikzpgf: Ch 26 Pattern Lbrary with \usetikzlibrary{patterns}
+
+BAD_MP_HATCH = ["o", "O"]  # Bad hatch/pattern correspondance
+UNUSED_PGF_HATCH = ["dots"]
+_MP_HATCH2PGF_HATCH = {
+    "-": "horizontal lines",
+    "|": "vertical lines",
+    "/": "north east lines",
+    "\\": "north west lines",
+    "+": "grid",
+    "x": "crosshatch",
+    ".": "crosshatch dots",
+    "*": "fivepointed stars",
+    "o": "sixpointed stars",
+    "O": "bricks",
+}
+
+
+def add_custom_pattern(mpl_hatch, pattern_name, pattern_definition):
+    pass
+
+
+def __validate_mpl_hatch(mpl_hatch):
+    if len(mpl_hatch) > 1:
+        warnings.warn(
+            f"tikzplotlib: Hatch '{mpl_hatch}' cannot be rendered. "
+            + "Only single character hatches are supported, e.g., "
+            + r"{'/', '\', '|', '-', '+', 'x', 'o', 'O', '.', '*'}. "
+            + f"Hatch '{mpl_hatch[0]}' will be used."
+        )
+        mpl_hatch = mpl_hatch[0]
+
+    if mpl_hatch in BAD_MP_HATCH:
+        warnings.warn(
+            f"tikzplotlib: The hatches {BAD_MP_HATCH} do not have good PGF"
+            + " counterparts."
+        )
+    return mpl_hatch
+
+
+def _mpl_hatch2pgfp_hatch(data, mpl_hatch, color_name, color_rgba):
+    """
+        Translates a hatch style of matplotlib to the corresponding style
+        in PGFPlots.
+    """
+    data["tikz libs"].add("patterns")
+
+    mpl_hatch = __validate_mpl_hatch(mpl_hatch)
+    try:
+        pgfplots_hatch = _MP_HATCH2PGF_HATCH.get(mpl_hatch)
+    except KeyError:
+        warnings.warn("tikzplotlib: The hatch", mpl_hatch, "cannot be handled.")
+        return data, []
+    else:
+        pattern_options = [f"pattern={pgfplots_hatch}"]
+        if color_name != "black":
+            # PGFPlots render patterns in 'pattern color' (default: black)
+            pattern_options += [f"pattern color={color_name}"]
+        if color_rgba[3] != 1:
+            ff = data["float format"]
+            # PGFPlots render patterns according to opacity fill.
+            pattern_options.append(("fill opacity=" + ff).format(color_rgba[3]))
+
+    # Add pattern as postaction to allow fill and pattern
+    # https://tex.stackexchange.com/questions/24964/
+    # how-to-combine-fill-and-pattern-in-a-pgfplot-bar-plot
+    hatch_postaction = f"postaction={{{', '.join(pattern_options)}}}"
+
+    return data, [hatch_postaction]
+
+
+if __name__ == "__main__":
+    import warnings
+    import matplotlib.pyplot as plt
+    import matplotlib
+
+    fig, ax = plt.subplots()
+
+    ax.bar(range(1, 5), range(1, 5), color="red", edgecolor="black", hatch="O")
+
+    for c in ax.get_children():
+        try:
+            hatch = c.get_hatch()
+        except AttributeError as error:
+            pass
+        else:
+            if hatch is not None:
+                print(c, hatch)
+        try:
+            color = c.get_hatch_color()
+        except AttributeError as error:
+            pass
+        else:
+            if color is not None:
+                print(c, color)
+        try:
+            lw = c.get_hatch_linewidth()
+        except AttributeError as error:
+            pass
+        else:
+            if lw is not None:
+                print(c, lw)
+
+    plt.show()