Attempt to set up nix-based docker for pict-rs

There's a bug when converting APNG files to WEBP files, which
imagemagick delegates to ffmpeg. When doing 'nix build' and running the
result, or running pict-rs in the dev shell, it works fine. In the
container, this doesn't work at all. imagemagick complains that there's
no media to convert, implying ffmpeg has output a zero-sized file.

This work is helping to narrow down exactly what pict-rs needs to run,
though. This still needs to be tested against h264, h265, vp8, vp9 and
av1.

flake.nix

@@ -15,13 +15,29 @@
       in
       {
         packages = rec {
+          imagemagick7_pict-rs = pkgs.callPackage ./nix/pkgs/imagemagick_pict-rs {};
+          ffmpeg6_pict-rs = pkgs.callPackage ./nix/pkgs/ffmpeg_pict-rs {};
+
           pict-rs = pkgs.callPackage ./pict-rs.nix {
             inherit (pkgs.darwin.apple_sdk.frameworks) Security;
+            inherit imagemagick7_pict-rs ffmpeg6_pict-rs;
           };
 
           default = pict-rs;
         };
 
+        docker = pkgs.dockerTools.buildLayeredImage {
+          name = "pict-rs";
+          tag = "latest";
+
+          contents = [ pkgs.tini self.packages.${system}.pict-rs ];
+
+          config = {
+            Entrypoint = [ "/bin/tini" "--" "/bin/pict-rs" ];
+            Cmd = [ "run" ];
+          };
+        };
+
         apps = rec {
           dev = flake-utils.lib.mkApp { drv = self.packages.${system}.pict-rs; };
           default = dev;
@@ -36,9 +52,9 @@
             curl
             diesel-cli
             exiftool
-            ffmpeg_6-full
             garage
-            imagemagick
+            self.packages.${system}.imagemagick7_pict-rs
+            self.packages.${system}.ffmpeg6_pict-rs
             jq
             minio-client
             rust-analyzer

nix/pkgs/ffmpeg_pict-rs/default.nix

@@ -0,0 +1,5 @@
+{ ffmpeg_6-headless }:
+
+ffmpeg_6-headless.override {
+  withWebp = true;
+}

nix/pkgs/imagemagick_pict-rs/default.nix

@@ -0,0 +1,23 @@
+{ imagemagick7 }:
+
+imagemagick7.override {
+    bzip2Support = true;
+    zlibSupport = true;
+    libX11Support = false;
+    libXtSupport = false;
+    fontconfigSupport = false;
+    freetypeSupport = false;
+    libjpegSupport = true;
+    djvulibreSupport = false;
+    lcms2Support = false;
+    openexrSupport = false;
+    libjxlSupport = true;
+    libpngSupport = true;
+    liblqr1Support = false;
+    librsvgSupport = false;
+    libtiffSupport = false;
+    libxml2Support = false;
+    openjpegSupport = true;
+    libwebpSupport = true;
+    libheifSupport = true;
+}

pict-rs.nix

@@ -1,6 +1,6 @@
 { exiftool
-, ffmpeg_6-full
+, ffmpeg6_pict-rs
-, imagemagick
+, imagemagick7_pict-rs
 , lib
 , makeWrapper
 , nixosTests
@@ -27,7 +27,7 @@ rustPlatform.buildRustPackage {
 
   postInstall = ''
     wrapProgram $out/bin/pict-rs \
-        --prefix PATH : "${lib.makeBinPath [ imagemagick ffmpeg_6-full exiftool ]}"
+        --prefix PATH : "${lib.makeBinPath [ imagemagick7_pict-rs ffmpeg6_pict-rs exiftool ]}"
   '';
 
   passthru.tests = { inherit (nixosTests) pict-rs; };