better color handling

Author: nschloe

src/tikzplotlib/_color.py

@@ -1,5 +1,51 @@
 import matplotlib as mpl
 import numpy as np
+import webcolors
+
+# RGB values (as taken from xcolor.dtx):
+builtin_colors = {
+    # List white first such that for gray values, the combination
+    # white!<x>!black is preferred over, e.g., gray!<y>!black. Note that
+    # the order of the dictionary is respected from Python 3.6 on.
+    "white": np.array([1, 1, 1]),
+    "lightgray": np.array([0.75, 0.75, 0.75]),
+    "gray": np.array([0.5, 0.5, 0.5]),
+    "darkgray": np.array([0.25, 0.25, 0.25]),
+    "black": np.array([0, 0, 0]),
+    #
+    "red": np.array([1, 0, 0]),
+    "green": np.array([0, 1, 0]),
+    "blue": np.array([0, 0, 1]),
+    "brown": np.array([0.75, 0.5, 0.25]),
+    "lime": np.array([0.75, 1, 0]),
+    "orange": np.array([1, 0.5, 0]),
+    "pink": np.array([1, 0.75, 0.75]),
+    "purple": np.array([0.75, 0, 0.25]),
+    "teal": np.array([0, 0.5, 0.5]),
+    "violet": np.array([0.5, 0, 0.5]),
+    # The colors cyan, magenta, yellow, and olive are also
+    # predefined by xcolor, but their RGB approximation of the
+    # native CMYK values is not very good. Don't use them here.
+}
+
+
+def _get_closest_colour_name(rgb):
+    match = None
+    mindiff = 1.0e15
+    for h, name in webcolors.CSS3_HEX_TO_NAMES.items():
+        r = int(h[1:3], 16)
+        g = int(h[3:5], 16)
+        b = int(h[5:7], 16)
+
+        diff = (rgb[0] - r) ** 2 + (rgb[1] - g) ** 2 + (rgb[2] - b) ** 2
+        if diff < mindiff:
+            match = name
+            mindiff = diff
+
+        if mindiff == 0:
+            break
+
+    return match, mindiff
 
 
 def mpl_color2xcolor(data, matplotlib_color):
@@ -12,66 +58,28 @@ def mpl_color2xcolor(data, matplotlib_color):
     if my_col[-1] == 0.0:
         return data, "none", my_col
 
-    xcol = None
-    # RGB values (as taken from xcolor.dtx):
-    available_colors = {
-        # List white first such that for gray values, the combination
-        # white!<x>!black is preferred over, e.g., gray!<y>!black. Note that
-        # the order of the dictionary is respected from Python 3.6 on.
-        "white": np.array([1, 1, 1]),
-        "lightgray": np.array([0.75, 0.75, 0.75]),
-        "gray": np.array([0.5, 0.5, 0.5]),
-        "darkgray": np.array([0.25, 0.25, 0.25]),
-        "black": np.array([0, 0, 0]),
-        #
-        "red": np.array([1, 0, 0]),
-        "green": np.array([0, 1, 0]),
-        "blue": np.array([0, 0, 1]),
-        "brown": np.array([0.75, 0.5, 0.25]),
-        "lime": np.array([0.75, 1, 0]),
-        "orange": np.array([1, 0.5, 0]),
-        "pink": np.array([1, 0.75, 0.75]),
-        "purple": np.array([0.75, 0, 0.25]),
-        "teal": np.array([0, 0.5, 0.5]),
-        "violet": np.array([0.5, 0, 0.5]),
-        # The colors cyan, magenta, yellow, and olive are also
-        # predefined by xcolor, but their RGB approximation of the
-        # native CMYK values is not very good. Don't use them here.
-    }
-
-    available_colors.update(data["custom colors"])
-
     # Check if it exactly matches any of the colors already available.
     # This case is actually treated below (alpha==1), but that loop
     # may pick up combinations with black before finding the exact
     # match. Hence, first check all colors.
-    for name, rgb in available_colors.items():
+    for name, rgb in builtin_colors.items():
         if all(my_col[:3] == rgb):
-            xcol = name
-            return data, xcol, my_col
-
-    # Check if my_col is a multiple of a predefined color and 'black'.
-    for name, rgb in available_colors.items():
-        if name == "black":
-            continue
+            return data, name, my_col
 
-        if rgb[0] != 0.0:
-            alpha = my_col[0] / rgb[0]
-        elif rgb[1] != 0.0:
-            alpha = my_col[1] / rgb[1]
-        else:
-            assert rgb[2] != 0.0
-            alpha = my_col[2] / rgb[2]
+    if np.all(my_col[0] == my_col[:3]):
+        # gray
+        # my_col[0] = 0.70123112 -> gray070
+        name = f"gray{int(100 * my_col[0]):03d}"
+        if name not in data["custom colors"]:
+            data["custom colors"][name] = ("gray", str(my_col[0]))
+        return data, name, my_col
 
-        # The cases 0.0 (my_col == black) and 1.0 (my_col == rgb) are
-        # already accounted for by checking in available_colors above.
-        if all(my_col[:3] == alpha * rgb) and 0.0 < alpha < 1.0:
-            ff = data["float format"]
-            xcol = name + f"!{alpha*100:{ff}}!black"
-            return data, xcol, my_col
+    # convert to RGB255
+    rgb255 = np.array(my_col[:3] * 255, dtype=int)
 
-    # Lookup failed, add it to the custom list.
-    xcol = "color" + str(len(data["custom colors"]))
-    data["custom colors"][xcol] = my_col[:3]
+    name, diff = _get_closest_colour_name(rgb255)
+    if diff > 0:
+        name = f"{name}{rgb255[0]}{rgb255[1]}{rgb255[2]}"
+    data["custom colors"][name] = ("RGB", ",".join([str(val) for val in rgb255]))
 
-    return data, xcol, my_col
+    return data, name, my_col