tests courtesy of Claude

lib/labelmaker_web/controllers/label_controller.ex

@@ -43,22 +43,34 @@ defmodule LabelmakerWeb.LabelController do
   end
 
   defp size_settings(args, %{height: "", width: ""} = options) do
+    # Escape % characters in label text to prevent ImageMagick property interpolation
+    escaped_label =
+      options.label
+      |> String.slice(0, Constants.max_label_length())
+      |> String.replace("%", "%%")
+
     args ++
       [
         "-pointsize",
         options.size,
-        "label:#{String.slice(options.label, 0, Constants.max_label_length())}"
+        "label:#{escaped_label}"
       ]
   end
 
   defp size_settings(args, %{align: alignment, height: height, width: width} = options) do
+    # Escape % characters in label text to prevent ImageMagick property interpolation
+    escaped_label =
+      options.label
+      |> String.slice(0, Constants.max_label_length())
+      |> String.replace("%", "%%")
+
     args ++
       [
         "-gravity",
         Tools.process_gravity(alignment),
         "-size",
         "#{width}x#{height}",
-        "caption:#{String.slice(options.label, 0, Constants.max_label_length())}"
+        "caption:#{escaped_label}"
       ]
   end
 
@@ -75,11 +87,19 @@ defmodule LabelmakerWeb.LabelController do
   end
 
   defp final_settings(args, options) do
+    # Escape % characters to prevent ImageMagick from interpreting them as property variables
+    comment =
+      options
+      |> Map.drop([:filepath, :link])
+      |> Jason.encode!()
+      |> inspect()
+      |> String.replace("%", "%%")
+
     args ++
       [
         "-set",
         "comment",
-        inspect(Jason.encode!(Map.drop(options, [:filepath, :link]))),
+        comment,
         options.filepath
       ]
   end