Add FontFile.to_imagefont() (#9419)

Tests/test_font_pcf.py

@@ -75,6 +75,16 @@ def test_draw(request: pytest.FixtureRequest, tmp_path: Path) -> None:
     assert_image_equal_tofile(im, "Tests/images/test_draw_pbm_target.png")
 
 
+def test_to_imagefont() -> None:
+    with open(fontname, "rb") as test_file:
+        pcffont = PcfFontFile.PcfFontFile(test_file)
+    imagefont = pcffont.to_imagefont()
+    im = Image.new("L", (130, 30), "white")
+    draw = ImageDraw.Draw(im)
+    draw.text((0, 0), message, "black", font=imagefont)
+    assert_image_equal_tofile(im, "Tests/images/test_draw_pbm_target.png")
+
+
 def test_textsize(request: pytest.FixtureRequest, tmp_path: Path) -> None:
     tempname = save_font(request, tmp_path)
     font = ImageFont.load(tempname)

Tests/test_fontfile.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from io import BytesIO
 from pathlib import Path
 
 import pytest
@@ -7,6 +8,15 @@ import pytest
 from PIL import FontFile, Image
 
 
+def test_puti16() -> None:
+    fp = BytesIO()
+    FontFile.puti16(fp, (0, 1, 2, 3, 4, 5, 6, 7, 8, 9))
+    assert fp.getvalue() == (
+        b"\x00\x00\x00\x01\x00\x02\x00\x03\x00\x04"
+        b"\x00\x05\x00\x06\x00\x07\x00\x08\x00\t"
+    )
+
+
 def test_compile() -> None:
     font = FontFile.FontFile()
     font.glyph[0] = ((0, 0), (0, 0, 0, 0), (0, 0, 0, 1), Image.new("L", (0, 0)))
@@ -24,5 +34,11 @@ def test_save(tmp_path: Path) -> None:
     tempname = str(tmp_path / "temp.pil")
 
     font = FontFile.FontFile()
-    with pytest.raises(ValueError):
+    with pytest.raises(ValueError, match="No bitmap created"):
         font.save(tempname)
+
+
+def test_to_imagefont() -> None:
+    font = FontFile.FontFile()
+    with pytest.raises(ValueError, match="No bitmap created"):
+        font.to_imagefont()

docs/reference/ImageFont.rst

@@ -8,10 +8,14 @@ The :py:mod:`~PIL.ImageFont` module defines a class with the same name. Instance
 this class store bitmap fonts, and are used with the
 :py:meth:`PIL.ImageDraw.ImageDraw.text` method.
 
-PIL uses its own font file format to store bitmap fonts, limited to 256 characters. You can use
-`pilfont.py <https://github.com/python-pillow/pillow-scripts/blob/main/Scripts/pilfont.py>`_
-from :pypi:`pillow-scripts` to convert BDF and
-PCF font descriptors (X window font formats) to this format.
+Pillow uses its own font file format to store bitmap fonts, limited to 256 characters. You
+can use :py:meth:`~PIL.FontFile.FontFile.to_imagefont` to convert BDF and PCF font
+descriptors (X Window font formats) to this format::
+
+    from PIL import PcfFontFile
+    with open("Tests/fonts/10x20-ISO8859-1.pcf", "rb") as fp:
+        font = PcfFontFile.PcfFontFile(fp)
+        imagefont = font.to_imagefont()
 
 Starting with version 1.1.4, PIL can be configured to support TrueType and
 OpenType fonts (as well as other font formats supported by the FreeType

src/PIL/FontFile.py

@@ -18,7 +18,7 @@ from __future__ import annotations
 import os
 from typing import BinaryIO
 
-from . import Image, _binary
+from . import Image, ImageFont, _binary
 
 WIDTH = 800
 
@@ -110,6 +110,22 @@ class FontFile:
                 self.bitmap.paste(im.crop(src), s)
                 self.metrics[i] = d, dst, s
 
+    def _encode_metrics(self) -> bytes:
+        values: list[int] = []
+        for i in range(256):
+            m = self.metrics[i]
+            if m:
+                values.extend(m[0] + m[1] + m[2])
+            else:
+                values.extend((0,) * 10)
+
+        data = bytearray()
+        for v in values:
+            if v < 0:
+                v += 65536
+            data += _binary.o16be(v)
+        return bytes(data)
+
     def save(self, filename: str) -> None:
         """Save font"""
 
@@ -126,9 +142,18 @@ class FontFile:
             fp.write(b"PILfont\n")
             fp.write(f";;;;;;{self.ysize};\n".encode("ascii"))  # HACK!!!
             fp.write(b"DATA\n")
-            for id in range(256):
-                m = self.metrics[id]
-                if not m:
-                    puti16(fp, (0,) * 10)
-                else:
-                    puti16(fp, m[0] + m[1] + m[2])
+            fp.write(self._encode_metrics())
+
+    def to_imagefont(self) -> ImageFont.ImageFont:
+        """Convert to ImageFont"""
+
+        self.compile()
+
+        # font data
+        if not self.bitmap:
+            msg = "No bitmap created"
+            raise ValueError(msg)
+
+        imagefont = ImageFont.ImageFont()
+        imagefont._load(self.bitmap, self._encode_metrics())
+        return imagefont

src/PIL/ImageFont.py

@@ -149,6 +149,9 @@ class ImageFont:
         # read PILfont metrics
         data = file.read(256 * 20)
 
+        self._load(image, data)
+
+    def _load(self, image: Image.Image, data: bytes) -> None:
         image.load()
 
         self.font = Image.core.font(image.im, data)