Add support for reading and writing grayscale PFM images

Tests/test_file_ppm.py

@@ -6,7 +6,12 @@
 
 from PIL import Image, PpmImagePlugin
 
-from .helper import assert_image_equal_tofile, assert_image_similar, hopper
+from .helper import (
+    assert_image_equal,
+    assert_image_equal_tofile,
+    assert_image_similar,
+    hopper,
+)
 
 # sample ppm stream
 TEST_FILE = "Tests/images/hopper.ppm"
@@ -100,6 +105,44 @@ def test_pnm(tmp_path):
         assert_image_equal_tofile(im, f)
 
 
+def test_pfm(tmp_path):
+    with Image.open("Tests/images/hopper.pfm") as im:
+        assert im.info["scale"] == 1.0
+        assert_image_equal(im, hopper("F"))
+
+        f = str(tmp_path / "tmp.pfm")
+        im.save(f)
+
+        assert_image_equal_tofile(im, f)
+
+
+def test_pfm_big_endian(tmp_path):
+    with Image.open("Tests/images/hopper_be.pfm") as im:
+        assert im.info["scale"] == 2.5
+        assert_image_equal(im, hopper("F"))
+
+        f = str(tmp_path / "tmp.pfm")
+        im.save(f)
+
+        assert_image_equal_tofile(im, f)
+
+
+@pytest.mark.parametrize(
+    "data",
+    [
+        b"Pf 1 1 NaN \0\0\0\0",
+        b"Pf 1 1 inf \0\0\0\0",
+        b"Pf 1 1 -inf \0\0\0\0",
+        b"Pf 1 1 0.0 \0\0\0\0",
+        b"Pf 1 1 -0.0 \0\0\0\0",
+    ],
+)
+def test_pfm_invalid(data):
+    with pytest.raises(ValueError):
+        with Image.open(BytesIO(data)):
+            pass
+
+
 @pytest.mark.parametrize(
     "plain_path, raw_path",
     (

docs/handbook/image-file-formats.rst

@@ -696,6 +696,24 @@ PCX
 
 Pillow reads and writes PCX files containing ``1``, ``L``, ``P``, or ``RGB`` data.
 
+PFM
+^^^
+
+.. versionadded:: 10.3.0
+
+Pillow reads and writes grayscale (Pf format) PFM files containing ``F`` data.
+
+Color (PF format) PFM files are not supported.
+
+Opening
+~~~~~~~
+
+The :py:func:`~PIL.Image.open` function sets the following
+:py:attr:`~PIL.Image.Image.info` properties:
+
+**scale**
+    The absolute value of the number stored in the *Scale Factor / Endianness* line.
+
 PNG
 ^^^
 

src/PIL/PpmImagePlugin.py

@@ -15,6 +15,8 @@
 #
 from __future__ import annotations
 
+import math
+
 from . import Image, ImageFile
 from ._binary import i16be as i16
 from ._binary import o8
@@ -35,6 +37,7 @@
     b"P6": "RGB",
     # extensions
     b"P0CMYK": "CMYK",
+    b"Pf": "F",
     # PIL extensions (for test purposes only)
     b"PyP": "P",
     b"PyRGBA": "RGBA",
@@ -43,7 +46,7 @@
 
 
 def _accept(prefix):
-    return prefix[0:1] == b"P" and prefix[1] in b"0123456y"
+    return prefix[0:1] == b"P" and prefix[1] in b"0123456fy"
 
 
 ##
@@ -110,6 +113,14 @@ def _open(self):
         if magic_number in (b"P1", b"P2", b"P3"):
             decoder_name = "ppm_plain"
         for ix in range(3):
+            if mode == "F" and ix == 2:
+                scale = float(self._read_token())
+                if not math.isfinite(scale) or scale == 0.0:
+                    msg = "scale must be finite and non-zero"
+                    raise ValueError(msg)
+                rawmode = "F;32F" if scale < 0 else "F;32BF"
+                self.info["scale"] = abs(scale)
+                continue
             token = int(self._read_token())
             if ix == 0:  # token is the x size
                 xsize = token
@@ -136,7 +147,8 @@ def _open(self):
                     elif maxval != 255:
                         decoder_name = "ppm"
 
-        args = (rawmode, 0, 1) if decoder_name == "raw" else (rawmode, maxval)
+        row_order = -1 if mode == "F" else 1
+        args = (rawmode, 0, row_order) if decoder_name == "raw" else (rawmode, maxval)
         self._size = xsize, ysize
         self.tile = [(decoder_name, (0, 0, xsize, ysize), self.fp.tell(), args)]
 
@@ -307,6 +319,7 @@ def decode(self, buffer):
 
 
 def _save(im, fp, filename):
+    row_order = 1
     if im.mode == "1":
         rawmode, head = "1;I", b"P4"
     elif im.mode == "L":
@@ -315,6 +328,9 @@ def _save(im, fp, filename):
         rawmode, head = "I;16B", b"P5"
     elif im.mode in ("RGB", "RGBA"):
         rawmode, head = "RGB", b"P6"
+    elif im.mode == "F":
+        rawmode, head = "F;32F", b"Pf"
+        row_order = -1
     else:
         msg = f"cannot write mode {im.mode} as PPM"
         raise OSError(msg)
@@ -326,7 +342,9 @@ def _save(im, fp, filename):
             fp.write(b"255\n")
         else:
             fp.write(b"65535\n")
-    ImageFile._save(im, fp, [("raw", (0, 0) + im.size, 0, (rawmode, 0, 1))])
+    elif head == b"Pf":
+        fp.write(b"-1.0\n")
+    ImageFile._save(im, fp, [("raw", (0, 0) + im.size, 0, (rawmode, 0, row_order))])
 
 
 #
@@ -339,6 +357,6 @@ def _save(im, fp, filename):
 Image.register_decoder("ppm", PpmDecoder)
 Image.register_decoder("ppm_plain", PpmPlainDecoder)
 
-Image.register_extensions(PpmImageFile.format, [".pbm", ".pgm", ".ppm", ".pnm"])
+Image.register_extensions(PpmImageFile.format, [".pbm", ".pgm", ".ppm", ".pnm", ".pfm"])
 
 Image.register_mime(PpmImageFile.format, "image/x-portable-anymap")