initial commit

deps/inkex/colors/converters.py

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+# coding=utf-8
+#
+# Copyright (C) 2018-2024 Martin Owens
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+#
+"""
+Basic color errors and common functions
+"""
+
+from collections import defaultdict
+
+from typing import Dict, List, Callable
+
+ConverterFunc = Callable[[float], List[float]]
+
+
+class Converters:
+    """
+    Record how colors can be converted between different spaces and provides
+    a way to path-find between multiple step conversions.
+    """
+
+    links: Dict[str, Dict[str, ConverterFunc]] = defaultdict(dict)
+    chains: Dict[str, List[List[str]]] = {}
+
+    @classmethod
+    def add_space(cls, color_cls):
+        """
+        Records the stated links between this class and other color spaces
+        """
+        for name, func in color_cls.__dict__.items():
+            if not name.startswith("convert_"):
+                continue
+            _, direction, space = name.split("_", 2)
+            from_name = color_cls.name if direction == "to" else space
+            to_name = color_cls.name if direction == "from" else space
+
+            if from_name != to_name:
+                if not isinstance(func, staticmethod):
+                    raise TypeError(f"Method '{name}' must be a static method.")
+                cls.links[from_name][to_name] = func.__func__
+
+    @classmethod
+    def get_chain(cls, source, target):
+        """
+        Get a chain of conversions between two color spaces, if possible.
+        """
+
+        def build_chains(chains, space):
+            new_chains = []
+            for chain in chains:
+                for hop in cls.links[space]:
+                    if hop not in chain:
+                        new_chains += build_chains([chain + [hop]], hop)
+            return chains + new_chains
+
+        if source not in cls.chains:
+            cls.chains[source] = build_chains([[source]], source)
+
+        chosen = None
+        for chain in cls.chains[source] or ():
+            if chain[-1] == target and (not chosen or len(chain) < len(chosen)):
+                chosen = chain
+        return chosen
+
+    @classmethod
+    def find_converter(cls, source, target):
+        """
+        Find a way to convert from source to target using any conversion functions.
+
+        Will hop from one space to another if needed.
+        """
+        func = None
+
+        # Passthough
+        if source == target:
+            return lambda self: self
+
+        if func is None:
+            chain = cls.get_chain(source.name, target.name)
+            if chain:
+                return cls.generate_converter(chain, source, target)
+
+        # Returning a function means we only run this function once, even when not found
+        def _error(self):
+            raise NotImplementedError(
+                f"Color space {source} can not be converted to {target}."
+            )
+
+        return _error
+
+    @classmethod
+    def generate_converter(cls, chain, source_cls, target_cls):
+        """
+        Put together a function that can do every step of the chain of conversions
+        """
+        # Build a list of functions to run
+        funcs = [cls.links[a][b] for a, b in zip(chain, chain[1:])]
+        funcs.insert(0, source_cls.to_units)
+        funcs.append(target_cls.from_units)
+
+        def _inner(values):
+            if hasattr(values, "alpha") and values.alpha is not None:
+                values = list(values) + [values.alpha]
+            for func in funcs:
+                values = func(*values)
+            return target_cls(values)
+
+        return _inner