Add functionality to export the CLF structure back to XML.

Author: MichaelMauderer

colour_clf_io/__init__.py

@@ -153,3 +153,12 @@ def parse_clf(text: str | bytes) -> ProcessList | None:
     xml = lxml.etree.fromstring(text)  # noqa: S320
 
     return ProcessList.from_xml(xml)
+
+
+def write_clf(process_list: ProcessList, path: str | Path | None = None) -> None | str:
+    xml = process_list.to_xml()
+    serialised = lxml.etree.tostring(xml)
+    if path is None:
+        return serialised.decode("utf-8")
+    with open(path, "wb") as f:
+        f.write(serialised)

colour_clf_io/elements.py

@@ -8,25 +8,28 @@
 
 from __future__ import annotations
 
+import itertools
 import typing
 from dataclasses import dataclass
 
 if typing.TYPE_CHECKING:
     import numpy.typing as npt
 
-if typing.TYPE_CHECKING:
-    import lxml.etree
+import lxml.etree
 
 from colour_clf_io.errors import ParsingError
 from colour_clf_io.parsing import (
     ParserConfig,
     XMLParsable,
+    XMLWritable,
     check_none,
     child_element,
     child_element_or_exception,
     map_optional,
     retrieve_attributes,
     retrieve_attributes_as_float,
+    set_attr_if_not_none,
+    set_element_if_not_none,
     three_floats,
 )
 from colour_clf_io.values import Channel
@@ -50,7 +53,7 @@
 
 
 @dataclass
-class Array(XMLParsable):
+class Array(XMLParsable, XMLWritable):
     """
     Represent an *Array* element.
 
@@ -124,6 +127,20 @@ def from_xml(
 
         return Array(values=values, dim=dimensions)
 
+    def to_xml(self) -> lxml.etree._Element:
+        xml = lxml.etree.Element("Array")
+        xml.set("dim", " ".join(map(str, self.dim)))
+        if len(self.dim) <= 1:
+            xml.text = "\n".join(self.values)
+        else:
+            row_length = self.dim[-1]
+            text = "\n".join(
+                " ".join(map(str, row))
+                for row in itertools.batched(self.values, row_length)
+            )
+            xml.text = text
+        return xml
+
     def as_array(self) -> npt.NDArray:
         """
         Convert the *CLF* element into a numpy array.
@@ -144,7 +161,7 @@ def as_array(self) -> npt.NDArray:
 
 
 @dataclass
-class CalibrationInfo(XMLParsable):
+class CalibrationInfo(XMLParsable, XMLWritable):
     """
     Represent a *CalibrationInfo* container element for a
     :class:`colour_clf_io.ProcessList` class instance.
@@ -227,9 +244,25 @@ def from_xml(
 
         return CalibrationInfo(**attributes)
 
+    def to_xml(self) -> lxml.etree._Element:
+        xml = lxml.etree.Element("CalibrationInfo")
+        set_attr_if_not_none(
+            xml, "DisplayDeviceSerialNum", self.display_device_serial_num
+        )
+        set_attr_if_not_none(
+            xml, "DisplayDeviceHostName", self.display_device_host_name
+        )
+        set_attr_if_not_none(xml, "OperatorName", self.operator_name)
+        set_attr_if_not_none(xml, "CalibrationDateTime", self.calibration_date_time)
+        set_attr_if_not_none(xml, "MeasurementProbe", self.measurement_probe)
+        set_attr_if_not_none(
+            xml, "CalibrationSoftwareName", self.calibration_software_name
+        )
+        return xml
+
 
 @dataclass
-class SOPNode(XMLParsable):
+class SOPNode(XMLParsable, XMLWritable):
     """
     Represent a *SOPNode* element for a :class:`colour_clf_io.ASC_CDL`
     *Process Node*.
@@ -312,6 +345,13 @@ def from_xml(
 
         return SOPNode(slope=slope, offset=offset, power=power)
 
+    def to_xml(self) -> lxml.etree._Element:
+        xml = lxml.etree.Element("SOPNode")
+        set_element_if_not_none(xml, "Slope", " ".join(map(str, self.slope)))
+        set_element_if_not_none(xml, "Offset", " ".join(map(str, self.offset)))
+        set_element_if_not_none(xml, "Power", " ".join(map(str, self.power)))
+        return xml
+
     @classmethod
     def default(cls) -> SOPNode:
         """
@@ -331,7 +371,7 @@ def default(cls) -> SOPNode:
 
 
 @dataclass
-class SatNode(XMLParsable):
+class SatNode(XMLParsable, XMLWritable):
     """
     Represent a *SatNode* element for a :class:`colour_clf_io.ASC_CDL`
     *Process Node*.
@@ -399,6 +439,11 @@ def from_xml(
 
         return SatNode(saturation=saturation)
 
+    def to_xml(self) -> lxml.etree._Element:
+        xml = lxml.etree.Element("SatNode")
+        set_element_if_not_none(xml, "Saturation", self.saturation)
+        return xml
+
     @classmethod
     def default(cls) -> SatNode:
         """
@@ -414,7 +459,7 @@ def default(cls) -> SatNode:
 
 
 @dataclass
-class Info(XMLParsable):
+class Info(XMLParsable, XMLWritable):
     """
     Represent an *Info* element.
 
@@ -520,9 +565,20 @@ def from_xml(xml: lxml.etree._Element | None, config: ParserConfig) -> Info | No
 
         return Info(calibration_info=calibration_info, **attributes)
 
+    def to_xml(self) -> lxml.etree._Element:
+        xml = lxml.etree.Element("Info")
+        set_attr_if_not_none(xml, "AppRelease", self.app_release)
+        set_attr_if_not_none(xml, "Copyright", self.copyright)
+        set_attr_if_not_none(xml, "Revision", self.revision)
+        set_attr_if_not_none(xml, "AcesTransformID", self.aces_transform_id)
+        set_attr_if_not_none(xml, "AcesUserName", self.aces_user_name)
+        if self.calibration_info is not None:
+            xml.append(self.calibration_info.to_xml())
+        return xml
+
 
 @dataclass
-class LogParams(XMLParsable):
+class LogParams(XMLParsable, XMLWritable):
     """
     Represent a *LogParams* element for a :class:`colour_clf_io.Log`
     *Process Node*.
@@ -641,14 +697,27 @@ def from_xml(
                 "lin_side_slope": "linSideSlope",
                 "lin_side_offset": "linSideOffset",
                 "lin_side_break": "linSideBreak",
-                "linear_slope": "linearSlope",
+                "linear_slope": "",
             },
         )
 
         channel = map_optional(Channel, xml.get("channel"))
 
         return LogParams(channel=channel, **attributes)
 
+    def to_xml(self) -> lxml.etree._Element:
+        xml = lxml.etree.Element("LogParams")
+        set_attr_if_not_none(xml, "base", self.base)
+        set_attr_if_not_none(xml, "logSideSlope", self.log_side_slope)
+        set_attr_if_not_none(xml, "logSideOffset", self.log_side_offset)
+        set_attr_if_not_none(xml, "linSideSlope", self.lin_side_slope)
+        set_attr_if_not_none(xml, "linSideOffset", self.lin_side_offset)
+        set_attr_if_not_none(xml, "linSideBreak", self.lin_side_break)
+        set_attr_if_not_none(xml, "linearSlope", self.linear_slope)
+        if self.channel is not None:
+            xml.set("channel", self.channel.value)
+        return xml
+
     @classmethod
     def default(cls) -> LogParams:
         """
@@ -673,7 +742,7 @@ def default(cls) -> LogParams:
 
 
 @dataclass
-class ExponentParams(XMLParsable):
+class ExponentParams(XMLParsable, XMLWritable):
     """
     Represent a *ExponentParams* element for a :class:`colour_clf_io.Exponent`
     *Process Node*.
@@ -772,6 +841,14 @@ def from_xml(
 
         return ExponentParams(channel=channel, exponent=exponent, **attributes)
 
+    def to_xml(self) -> lxml.etree._Element:
+        xml = lxml.etree.Element("ExponentParams")
+        set_attr_if_not_none(xml, "exponent", self.exponent)
+        set_attr_if_not_none(xml, "offset", self.offset)
+        if self.channel is not None:
+            xml.set("channel", self.channel.value)
+        return xml
+
     @classmethod
     def default(cls) -> ExponentParams:
         """

colour_clf_io/parsing.py

@@ -18,8 +18,7 @@
     from collections.abc import Callable, Iterable
     from typing import Any
 
-if typing.TYPE_CHECKING:
-    import lxml.etree
+import lxml.etree
 
 from colour_clf_io.errors import ParsingError
 
@@ -120,6 +119,25 @@ def from_xml(
         """
 
 
+class XMLWritable(ABC):
+    """
+    Define the base class for objects that can be serialised to XML.
+
+    This is an :class:`ABCMeta` abstract class that must be inherited by
+    sub-classes.
+
+    Methods
+    -------
+    -   :meth:`~colour_lf_io.parsing.XMLParsable.to_xml`
+    """
+
+    @abstractmethod
+    def to_xml(self) -> lxml.etree._Element:
+        """
+        Serialise this object as an XML object.
+        """
+
+
 def map_optional(function: Callable, value: Any | None) -> Any:
     """
     Apply the given function to given ``value`` if ``value`` is not ``None``.
@@ -490,3 +508,14 @@ def three_floats(text: str | None) -> tuple[float, float, float]:
     values = tuple(map(float, parts))
     # Note: Repacking here to satisfy type check.
     return values[0], values[1], values[2]
+
+
+def set_attr_if_not_none(node, attr, value):
+    if value is not None:
+        node.set(attr, str(value))
+
+
+def set_element_if_not_none(node, name, value):
+    if value is not None and value != "":
+        child = lxml.etree.SubElement(node, name)
+        child.text = str(value)

colour_clf_io/process_list.py

@@ -19,6 +19,8 @@
     check_none,
     element_as_text,
     elements_as_text_list,
+    set_attr_if_not_none,
+    set_element_if_not_none,
 )
 from colour_clf_io.process_nodes import (
     ProcessNode,
@@ -200,3 +202,22 @@ def from_xml(xml: lxml.etree._Element | None) -> ProcessList | None:
             info=info,
             description=description,
         )
+
+    def to_xml(self) -> lxml.etree._Element:
+        xml = lxml.etree.Element("ProcessList")
+        set_attr_if_not_none(xml, "id", self.id)
+        set_attr_if_not_none(xml, "compCLFversion", self.compatible_CLF_version)
+        set_attr_if_not_none(xml, "name", self.name)
+        set_attr_if_not_none(xml, "inverseOf", self.inverse_of)
+        set_element_if_not_none(xml, "InputDescriptor", self.input_descriptor)
+        set_element_if_not_none(xml, "OutputDescriptor", self.output_descriptor)
+        if self.info:
+            xml.append(self.info.to_xml())
+        for description_text in self.description:
+            description_element = lxml.etree.SubElement(xml, "Description")
+            description_element.text = description_text
+        # TODO: we might have to store a single list of children in order to preserve
+        #   ordering of description and process nodes
+        for process_node in self.process_nodes:
+            xml.append(process_node.to_xml())
+        return xml