logo: Provide an easy path to optimized SVGs and exported PNGs

The non-logo files are not part of the build, as they are files made for
specific usage, and should not be part of the NixOS assets for general
usage.

default.nix

@@ -28,4 +28,5 @@
       makeFlags = [ "prefix=$(out)" ];
     }
   ) {};
+  logo = pkgs.callPackage ./logo/package.nix {};
 }

logo/README.md

@@ -56,6 +56,17 @@ white, keeping the spacing exact.
 This variant is monochrome, with the shadow gradients baked-in as opacity
 changes.
 
+### Optimized version
+
+The SVG files in this directory are the authoring files.
+
+In other words, they are busy with inkscape-specific properties, used when
+editing the files.
+
+If what is needed is a file optimized for size, and for using as an asset,
+the Nix expression in this directory can be used to produce optimized SVGs.
+
+
 License
 -------
 

logo/default.nix

@@ -0,0 +1 @@
+(import ../. {}).logo

logo/package.nix

@@ -0,0 +1,38 @@
+{ runCommand
+, lib
+, inkscape
+, nodePackages
+}:
+
+runCommand "nixos-artwork-logos" {
+  logos = [
+    # The snowflake-only variants
+    "nix-snowflake-colours"
+    "nix-snowflake-white"
+
+    # The horizontal variants
+    "nixos"
+    "nixos-white"
+
+    # The vertical variant
+    "nixos-text-below"
+  ];
+  src = lib.cleanSource ./.;
+  nativeBuildInputs = [
+    inkscape
+    nodePackages.svgo
+  ];
+} ''
+  PS4=" $ "
+  for f in $logos; do
+    mkdir -p $out
+    printf ":: ⇒ %s\n" "$f"
+    (set -x
+    inkscape --export-background-opacity=0 --export-plain-svg --export-filename=$out/$f.svg "$src/$f.svg"
+    inkscape --export-background-opacity=0 --export-filename=$out/$f.png "$src/$f.svg"
+    )
+  done
+  (set -x
+  svgo --pretty --multipass --folder "$out"
+  )
+''