FIX: Standardize image-text converter font default to None

pyrit/converter/add_text_image_converter.py

@@ -33,7 +33,7 @@ def __init__(
         self,
         *,
         text_to_add: str,
-        font_name: str = "helvetica.ttf",
+        font_name: str | None = None,
         color: tuple[int, int, int] = (0, 0, 0),
         font_size: int = 15,
         x_pos: int = 10,
@@ -44,7 +44,8 @@ def __init__(
 
         Args:
             text_to_add (str): Text to add to an image.
-            font_name (str): Path of font to use. Must be a TrueType font (.ttf). Defaults to "helvetica.ttf".
+            font_name (str | None): Path of font to use. Must be a TrueType font (.ttf).
+                Defaults to None which uses Pillow's built-in default font.
             color (tuple): Color to print text in, using RGB values. Defaults to (0, 0, 0).
             font_size (int): Size of font to use. Defaults to 15.
             x_pos (int): X coordinate to place text in (0 is left most). Defaults to 10.
@@ -55,7 +56,7 @@ def __init__(
         """
         if text_to_add.strip() == "":
             raise ValueError("Please provide valid text_to_add value")
-        if not font_name.endswith(".ttf"):
+        if font_name is not None and not font_name.endswith(".ttf"):
             raise ValueError("The specified font must be a TrueType font with a .ttf extension")
         self._text_to_add = text_to_add
         self._font_name = font_name
@@ -91,10 +92,13 @@ def _load_font(self) -> FreeTypeFont:
         Returns:
             FreeTypeFont: The loaded font object. Falls back to Pillow's built-in default font on error.
         """
+        font_name = self._font_name
+        if font_name is None:
+            return cast("FreeTypeFont", ImageFont.load_default(size=self._font_size))
         try:
-            return ImageFont.truetype(self._font_name, self._font_size)
+            return ImageFont.truetype(font_name, self._font_size)
         except OSError:
-            logger.warning(f"Cannot open font resource: {self._font_name}. Using Pillow built-in default font.")
+            logger.warning(f"Cannot open font resource: {font_name}. Using Pillow built-in default font.")
             return cast("FreeTypeFont", ImageFont.load_default(size=self._font_size))
 
     def _add_text_to_image(self, image: Image.Image) -> Image.Image:

tests/unit/converter/test_add_text_image_converter.py

@@ -19,18 +19,20 @@ def text_image_converter_sample_image_bytes():
     return img_bytes.getvalue()
 
 
-def test_add_text_image_converter_initialization():
+def test_add_text_image_converter_initialization(caplog):
     converter = AddTextImageConverter(
-        text_to_add="Sample text", font_name="helvetica.ttf", color=(255, 255, 255), font_size=20, x_pos=10, y_pos=10
+        text_to_add="Sample text", color=(255, 255, 255), font_size=20, x_pos=10, y_pos=10
     )
     assert converter._text_to_add == "Sample text"
-    assert converter._font_name == "helvetica.ttf"
+    assert converter._font_name is None
     assert converter._color == (255, 255, 255)
     assert converter._font_size == 20
     assert converter._x_pos == 10
     assert converter._y_pos == 10
     assert converter._font is not None
     assert type(converter._font) is ImageFont.FreeTypeFont
+    # The default (None) uses Pillow's built-in font directly, so no font-loading warning is emitted.
+    assert not any("Cannot open font resource" in record.message for record in caplog.records)
 
 
 def test_add_text_image_converter_invalid_font():
@@ -40,7 +42,7 @@ def test_add_text_image_converter_invalid_font():
 
 def test_add_text_image_converter_invalid_text_to_add():
     with pytest.raises(ValueError):
-        AddTextImageConverter(text_to_add="", font_name="helvetica.ttf")
+        AddTextImageConverter(text_to_add="")
 
 
 def test_add_text_image_converter_fallback_to_default_font(text_image_converter_sample_image_bytes, caplog):
@@ -66,7 +68,7 @@ def test_add_text_image_converter_fallback_to_default_font(text_image_converter_
 
 
 def test_text_image_converter_add_text_to_image(text_image_converter_sample_image_bytes):
-    converter = AddTextImageConverter(text_to_add="Hello, World!", font_name="helvetica.ttf", color=(255, 255, 255))
+    converter = AddTextImageConverter(text_to_add="Hello, World!", color=(255, 255, 255))
     image = Image.open(BytesIO(text_image_converter_sample_image_bytes))
     try:
         pixels_before = list(image.get_flattened_data())