[doc] Include variants for dark/light mode of data-model

doc/data-model.rst

@@ -11,7 +11,13 @@
 The data model implemented in this package is summarized in the following
 figure:
 
-.. figure:: img/data-model.png
+.. image:: img/data-model-lite.png
+   :align: center
+   :class: only-light
+
+.. image:: img/data-model-dark.png
+   :align: center
+   :class: only-dark
 
 
 Each of the elements is described next.

doc/img/Makefile

+# SPDX-FileCopyrightText: Copyright © 2024 Idiap Research Institute <contact@idiap.ch>
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+MAINFILES=data-model.dot
+LITE_PNGFILES=$(MAINFILES:%.dot=%-lite.png)
+DARK_PNGFILES=$(MAINFILES:%.dot=%-dark.png)
+
+.PHONY: FORCE_MAKE clean
+
+all: $(LITE_PNGFILES) $(DARK_PNGFILES)
+
+%-lite.png: %.dot FORCE_MAKE
+	dot -Tpng -Gbgcolor="white" -Nfontcolor="black" -Ncolor="black" -Efontcolor="black" -Ecolor="black" -o $@ $<
+
+%-dark.png: %.dot FORCE_MAKE
+	dot -Tpng -Gbgcolor="black" -Nfontcolor="white" -Ncolor="white" -Efontcolor="white" -Ecolor="white" -o $@ $<
+
+clean:
+	@rm -vf $(LITE_PNGFILES) $(DARK_PNGFILES) $(shell find . -name "*~")

doc/img/data-model.dot

@@ -3,7 +3,7 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 
 digraph G {
-    rankdir = T;
+    rankdir = TB;
 
     fontname = "Helvetica"