Add scannability (image correctness) tests to ensure proper addon rendering. Fix addon rendering by adding quiet zone.

Author: dekoza

.github/workflows/tests.yml

@@ -27,6 +27,15 @@ jobs:
           cache: pip
           cache-dependency-path: |
             pyproject.toml
+      - name: Install system dependencies (Linux)
+        if: runner.os == 'Linux'
+        run: sudo apt-get update && sudo apt-get install -y libzbar0 libcairo2-dev
+      - name: Install system dependencies (macOS)
+        if: runner.os == 'macOS'
+        run: brew install zbar cairo
+      - name: Install system dependencies (Windows)
+        if: runner.os == 'Windows'
+        run: choco install zbar
       - name: Install test dependency
         run: pip install tox
       - name: Run tests

barcode/charsets/addons.py

@@ -7,6 +7,7 @@
 from __future__ import annotations
 
 # Addon guard patterns
+ADDON_QUIET_ZONE = "000000000"  # 9-module separator between main code and addon (GS1 spec)
 ADDON_START = "1011"  # Start guard for addon
 ADDON_SEPARATOR = "01"  # Separator between addon digits
 

barcode/charsets/ean.py

@@ -2,6 +2,7 @@
 
 from barcode.charsets.addons import ADDON2_PARITY
 from barcode.charsets.addons import ADDON5_PARITY
+from barcode.charsets.addons import ADDON_QUIET_ZONE
 from barcode.charsets.addons import ADDON_SEPARATOR
 from barcode.charsets.addons import ADDON_START
 
@@ -64,6 +65,7 @@
 __all__ = [
     "ADDON2_PARITY",
     "ADDON5_PARITY",
+    "ADDON_QUIET_ZONE",
     "ADDON_SEPARATOR",
     "ADDON_START",
     "CODES",

barcode/charsets/upc.py

@@ -3,6 +3,7 @@
 from barcode.charsets.addons import ADDON2_PARITY
 from barcode.charsets.addons import ADDON5_PARITY
 from barcode.charsets.addons import ADDON_CODES
+from barcode.charsets.addons import ADDON_QUIET_ZONE
 from barcode.charsets.addons import ADDON_SEPARATOR
 from barcode.charsets.addons import ADDON_START
 
@@ -40,6 +41,7 @@
     "ADDON2_PARITY",
     "ADDON5_PARITY",
     "ADDON_CODES",
+    "ADDON_QUIET_ZONE",
     "ADDON_SEPARATOR",
     "ADDON_START",
     "CODES",

barcode/ean.py

@@ -146,14 +146,20 @@ def build(self) -> list[str]:
     def _build_addon(self) -> str:
         """Builds the addon barcode pattern (EAN-2 or EAN-5).
 
-        :returns: The addon pattern as string
+        :returns: The addon pattern as string (including quiet zone separator)
         """
         if not self.addon:
             return ""
 
+        # Add quiet zone (9 modules) before addon per GS1 specification
+        code = _ean.ADDON_QUIET_ZONE
+
         if len(self.addon) == 2:
-            return self._build_addon2()
-        return self._build_addon5()
+            code += self._build_addon2()
+        else:
+            code += self._build_addon5()
+
+        return code
 
     def _build_addon2(self) -> str:
         """Builds EAN-2 addon pattern.

barcode/upc.py

@@ -128,14 +128,20 @@ def build(self) -> list[str]:
     def _build_addon(self) -> str:
         """Builds the addon barcode pattern (EAN-2 or EAN-5).
 
-        :returns: The addon pattern as string
+        :returns: The addon pattern as string (including quiet zone separator)
         """
         if not self.addon:
             return ""
 
+        # Add quiet zone (9 modules) before addon per GS1 specification
+        code = _upc.ADDON_QUIET_ZONE
+
         if len(self.addon) == 2:
-            return self._build_addon2()
-        return self._build_addon5()
+            code += self._build_addon2()
+        else:
+            code += self._build_addon5()
+
+        return code
 
     def _build_addon2(self) -> str:
         """Builds EAN-2 addon pattern.

docs/changelog.rst

@@ -9,6 +9,10 @@ current
   book prices.
 * Added support for EAN-2 and EAN-5 addons to UPC-A barcodes via the ``addon``
   parameter, following the same interface as EAN-13.
+* Addon rendering includes a 9-module quiet zone separator between the
+  main barcode and the addon, as required by the GS1 specification. This ensures
+  proper scanning of barcodes with addons.
+* Added scannability tests for EAN-2 and EAN-5 addons using the ``pyzbar`` library.
 * Fixed ISSN to accept full EAN-13 format (13 digits starting with 977) and
   preserve digits 11-12 (sequence variant) instead of always replacing them
   with "00".