Dark mode: Invert some images (#2409)

Co-authored-by: Adam Turner <9087854+aa-turner@users.noreply.github.com>

pep-0001.txt

@@ -439,6 +439,7 @@ an API can replace version 1.
 The possible paths of the status of PEPs are as follows:
 
 .. image:: pep-0001-process_flow.png
+   :class: invert-in-dark-mode
    :alt: PEP process flow diagram
 
 While not shown in the diagram, "Accepted" PEPs may technically move to

pep-0458.txt

@@ -489,6 +489,7 @@ trusted to sign for files available on PyPI.  The next two sections cover the
 details of signing repository files and the types of keys used for each role.
 
 .. image:: pep-0458-1.png
+   :class: invert-in-dark-mode
 
 Figure 1: An overview of the role metadata available on PyPI.
 

pep-0480.txt

@@ -207,6 +207,7 @@ packages in the minimum security model, but not in the maximum model, without
 also compromising a developer's key.
 
 .. image:: pep-0480-1.png
+   :class: invert-in-dark-mode
 
 Figure 1: An overview of the metadata layout in the maximum security model.
 The maximum security model supports continuous delivery and survivable key

pep-0495.txt

@@ -387,6 +387,7 @@ the ``fold`` attribute depending on the kind of the transition.
 .. image:: pep-0495-fold-2.png
   :align: center
   :width: 60%
+  :class: invert-in-dark-mode
 
 The sketch above illustrates the relationship between the UTC and
 local time around a fall-back transition.  The zig-zag line is a graph
@@ -412,6 +413,7 @@ effect after the transition should be used.
 .. image:: pep-0495-gap.png
   :align: center
   :width: 60%
+  :class: invert-in-dark-mode
 
 The sketch above illustrates the relationship between the UTC and
 local time around a spring-forward transition.  At the transition, the

pep-0525.txt

@@ -389,6 +389,7 @@ iterated:
 .. image:: pep-0525-1.png
    :align: center
    :width: 80%
+   :class: invert-in-dark-mode
 
 
 PyAsyncGenASend and PyAsyncGenAThrow

pep-0532.txt

@@ -681,6 +681,7 @@ breaking protocol (although it glosses over the technical detail of looking
 up the special methods via the type rather than the instance):
 
 .. image:: pep-0532/circuit-breaking-protocol.svg
+   :class: invert-in-dark-mode
    :alt: diagram of circuit breaking protocol applied to ternary expression
 
 We will work through the following expression::

pep-0550.rst

@@ -1568,6 +1568,7 @@ Appendix: HAMT Performance Analysis
 .. figure:: pep-0550-hamt_vs_dict-v2.png
    :align: center
    :width: 100%
+   :class: invert-in-dark-mode
 
    Figure 1.  Benchmark code can be found here: [9]_.
 
@@ -1581,6 +1582,7 @@ The above chart demonstrates that:
 .. figure:: pep-0550-lookup_hamt.png
    :align: center
    :width: 100%
+   :class: invert-in-dark-mode
 
    Figure 2.  Benchmark code can be found here: [10]_.
 

pep-0603.rst

@@ -298,6 +298,7 @@ Performance
 .. figure:: pep-0603-hamt_vs_dict.png
    :align: center
    :width: 100%
+   :class: invert-in-dark-mode
 
    Figure 1.  Benchmark code can be found here: [3]_.
 
@@ -312,6 +313,7 @@ The above chart demonstrates that:
 .. figure:: pep-0603-lookup_hamt.png
    :align: center
    :width: 100%
+   :class: invert-in-dark-mode
 
    Figure 2.  Benchmark code can be found here: [4]_.
 

pep-3147.txt

@@ -318,6 +318,7 @@ Here is a flow chart describing how modules are loaded:
 
 .. image:: pep-3147-1.png
    :scale: 75
+   :class: invert-in-dark-mode
 
 
 Alternative Python implementations

pep_sphinx_extensions/pep_theme/static/dark.css

@@ -16,3 +16,7 @@
     --colour-inline-code: #333;
     --colour-warning: #900;
 }
+
+img.invert-in-dark-mode {
+    filter: invert(1);
+}