Add abstract BaseImageFont class (#9595)

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Author: radarhere

docs/reference/ImageFont.rst

@@ -66,15 +66,21 @@ Functions
 Methods
 -------
 
+.. autoclass:: PIL.ImageFont.BaseImageFont
+    :members:
+
 .. autoclass:: PIL.ImageFont.ImageFont
     :members:
+    :show-inheritance:
 
 .. autoclass:: PIL.ImageFont.FreeTypeFont
     :members:
+    :show-inheritance:
 
 .. autoclass:: PIL.ImageFont.TransposedFont
     :members:
     :undoc-members:
+    :show-inheritance:
 
 Constants
 ---------

src/PIL/ImageDraw.py

@@ -36,15 +36,15 @@
 from collections.abc import Sequence
 from typing import cast
 
-from . import Image, ImageColor, ImageText
+from . import Image, ImageColor, ImageFont, ImageText
 
 TYPE_CHECKING = False
 if TYPE_CHECKING:
     from collections.abc import Callable
     from types import ModuleType
     from typing import Any, AnyStr
 
-    from . import ImageDraw2, ImageFont
+    from . import ImageDraw2
     from ._typing import Coords, _Ink
 
 # experimental access to the outline API
@@ -59,9 +59,7 @@
 
 
 class ImageDraw:
-    font: (
-        ImageFont.ImageFont | ImageFont.FreeTypeFont | ImageFont.TransposedFont | None
-    ) = None
+    font: ImageFont.BaseImageFont | None = None
 
     def __init__(self, im: Image.Image, mode: str | None = None) -> None:
         """
@@ -105,7 +103,7 @@ def __init__(self, im: Image.Image, mode: str | None = None) -> None:
 
     def getfont(
         self,
-    ) -> ImageFont.ImageFont | ImageFont.FreeTypeFont | ImageFont.TransposedFont:
+    ) -> ImageFont.BaseImageFont:
         """
         Get the current default font.
 
@@ -125,17 +123,11 @@ def getfont(
         :returns: An image font."""
         if not self.font:
             # FIXME: should add a font repository
-            from . import ImageFont
-
             self.font = ImageFont.load_default()
         return self.font
 
-    def _getfont(
-        self, font_size: float | None
-    ) -> ImageFont.ImageFont | ImageFont.FreeTypeFont | ImageFont.TransposedFont:
+    def _getfont(self, font_size: float | None) -> ImageFont.BaseImageFont:
         if font_size is not None:
-            from . import ImageFont
-
             return ImageFont.load_default(font_size)
         else:
             return self.getfont()
@@ -540,12 +532,7 @@ def text(
         xy: tuple[float, float],
         text: AnyStr | ImageText.Text[AnyStr],
         fill: _Ink | None = None,
-        font: (
-            ImageFont.ImageFont
-            | ImageFont.FreeTypeFont
-            | ImageFont.TransposedFont
-            | None
-        ) = None,
+        font: ImageFont.BaseImageFont | None = None,
         anchor: str | None = None,
         spacing: float = 4,
         align: str = "left",
@@ -600,26 +587,26 @@ def draw_text(ink: int, stroke_width: float = 0) -> None:
                 x = int(line.x)
                 y = int(line.y)
                 start = (math.modf(line.x)[0], math.modf(line.y)[0])
-                try:
-                    mask, offset = image_text.font.getmask2(  # type: ignore[union-attr,misc]
+                if isinstance(image_text.font, ImageFont.FreeTypeFont):
+                    mask, offset = image_text.font.getmask2(
                         line.text,
                         mode,
-                        direction=direction,
-                        features=features,
-                        language=language,
-                        stroke_width=stroke_width,
+                        direction,
+                        features,
+                        language,
+                        stroke_width,
+                        line.anchor,
+                        ink,
+                        start,
                         stroke_filled=True,
-                        anchor=line.anchor,
-                        ink=ink,
-                        start=start,
                         *args,
                         **kwargs,
                     )
                     x += offset[0]
                     y += offset[1]
-                except AttributeError:
+                else:
                     try:
-                        mask = image_text.font.getmask(  # type: ignore[misc]
+                        mask = image_text.font.getmask(
                             line.text,
                             mode,
                             direction,
@@ -664,12 +651,7 @@ def multiline_text(
         xy: tuple[float, float],
         text: AnyStr,
         fill: _Ink | None = None,
-        font: (
-            ImageFont.ImageFont
-            | ImageFont.FreeTypeFont
-            | ImageFont.TransposedFont
-            | None
-        ) = None,
+        font: ImageFont.BaseImageFont | None = None,
         anchor: str | None = None,
         spacing: float = 4,
         align: str = "left",
@@ -702,12 +684,7 @@ def multiline_text(
     def textlength(
         self,
         text: AnyStr,
-        font: (
-            ImageFont.ImageFont
-            | ImageFont.FreeTypeFont
-            | ImageFont.TransposedFont
-            | None
-        ) = None,
+        font: ImageFont.BaseImageFont | None = None,
         direction: str | None = None,
         features: list[str] | None = None,
         language: str | None = None,
@@ -734,12 +711,7 @@ def textbbox(
         self,
         xy: tuple[float, float],
         text: AnyStr,
-        font: (
-            ImageFont.ImageFont
-            | ImageFont.FreeTypeFont
-            | ImageFont.TransposedFont
-            | None
-        ) = None,
+        font: ImageFont.BaseImageFont | None = None,
         anchor: str | None = None,
         spacing: float = 4,
         align: str = "left",
@@ -767,12 +739,7 @@ def multiline_textbbox(
         self,
         xy: tuple[float, float],
         text: AnyStr,
-        font: (
-            ImageFont.ImageFont
-            | ImageFont.FreeTypeFont
-            | ImageFont.TransposedFont
-            | None
-        ) = None,
+        font: ImageFont.BaseImageFont | None = None,
         anchor: str | None = None,
         spacing: float = 4,
         align: str = "left",

src/PIL/ImageFont.py

@@ -27,6 +27,7 @@
 
 from __future__ import annotations
 
+import abc
 import base64
 import os
 import sys
@@ -91,7 +92,27 @@ def _string_length_check(text: str | bytes | bytearray) -> None:
 # --------------------------------------------------------------------
 
 
-class ImageFont:
+class BaseImageFont(abc.ABC):
+    """Used by ImageDraw and ImageText"""
+
+    @abc.abstractmethod
+    def getbbox(
+        self, text: str | bytes | bytearray, *args: Any, **kwargs: Any
+    ) -> tuple[float, float, float, float]:
+        pass
+
+    @abc.abstractmethod
+    def getmask(
+        self, text: str | bytes, mode: str = "", *args: Any, **kwargs: Any
+    ) -> Image.core.ImagingCore:
+        pass
+
+    @abc.abstractmethod
+    def getlength(self, text: str | bytes, *args: Any, **kwargs: Any) -> float:
+        pass
+
+
+class ImageFont(BaseImageFont):
     """PIL font wrapper"""
 
     font: ImagingFont
@@ -215,7 +236,7 @@ def getlength(
 # <b>truetype</b> factory function to create font objects.
 
 
-class FreeTypeFont:
+class FreeTypeFont(BaseImageFont):
     """FreeType font wrapper (requires _imagingft service)"""
 
     font: Font
@@ -723,7 +744,7 @@ def set_variation_by_axes(self, axes: list[float]) -> None:
         self.font.setvaraxes(axes)
 
 
-class TransposedFont:
+class TransposedFont(BaseImageFont):
     """Wrapper for writing rotated or mirrored text"""
 
     def __init__(

src/PIL/ImageText.py

@@ -7,8 +7,6 @@
 from . import ImageFont
 from ._typing import _Ink
 
-Font = ImageFont.ImageFont | ImageFont.FreeTypeFont | ImageFont.TransposedFont
-
 
 class _Line(NamedTuple):
     x: float
@@ -27,7 +25,7 @@ def __init__(
         text: Text[AnyStr],
         width: int,
         height: int | None = None,
-        font: Font | None = None,
+        font: ImageFont.BaseImageFont | None = None,
     ) -> None:
         self.text: Text[AnyStr] = text
         self.width = width
@@ -97,7 +95,7 @@ class Text(Generic[AnyStr]):
     def __init__(
         self,
         text: AnyStr,
-        font: Font | None = None,
+        font: ImageFont.BaseImageFont | None = None,
         mode: str = "RGB",
         spacing: float = 4,
         direction: str | None = None,
@@ -449,7 +447,10 @@ def _split(
         return parts
 
     def _get_bbox(
-        self, text: str | bytes, font: Font | None = None, anchor: str | None = None
+        self,
+        text: str | bytes,
+        font: ImageFont.BaseImageFont | None = None,
+        anchor: str | None = None,
     ) -> tuple[float, float, float, float]:
         return (font or self.font).getbbox(
             text,