Added DDS support for uncompressed L and LA images

Tests/test_file_dds.py

@@ -22,6 +22,8 @@
 TEST_FILE_DX10_BC7_UNORM_SRGB = "Tests/images/DXGI_FORMAT_BC7_UNORM_SRGB.dds"
 TEST_FILE_DX10_R8G8B8A8 = "Tests/images/argb-32bpp_MipMaps-1.dds"
 TEST_FILE_DX10_R8G8B8A8_UNORM_SRGB = "Tests/images/DXGI_FORMAT_R8G8B8A8_UNORM_SRGB.dds"
+TEST_FILE_UNCOMPRESSED_L = "Tests/images/uncompressed_l.dds"
+TEST_FILE_UNCOMPRESSED_L_WITH_ALPHA = "Tests/images/uncompressed_la.dds"
 TEST_FILE_UNCOMPRESSED_RGB = "Tests/images/hopper.dds"
 TEST_FILE_UNCOMPRESSED_RGB_WITH_ALPHA = "Tests/images/uncompressed_rgb.dds"
 
@@ -194,26 +196,24 @@ def test_unimplemented_dxgi_format():
             pass
 
 
-def test_uncompressed_rgb():
-    """Check uncompressed RGB images can be opened"""
-
-    # convert -format dds -define dds:compression=none hopper.jpg hopper.dds
-    with Image.open(TEST_FILE_UNCOMPRESSED_RGB) as im:
-        assert im.format == "DDS"
-        assert im.mode == "RGB"
-        assert im.size == (128, 128)
-
-        assert_image_equal_tofile(im, "Tests/images/hopper.png")
+@pytest.mark.parametrize(
+    ("mode", "size", "test_file"),
+    [
+        ("L", (128, 128), TEST_FILE_UNCOMPRESSED_L),
+        ("LA", (128, 128), TEST_FILE_UNCOMPRESSED_L_WITH_ALPHA),
+        ("RGB", (128, 128), TEST_FILE_UNCOMPRESSED_RGB),
+        ("RGBA", (800, 600), TEST_FILE_UNCOMPRESSED_RGB_WITH_ALPHA),
+    ],
+)
+def test_uncompressed(mode, size, test_file):
+    """Check uncompressed images can be opened"""
 
-    # Test image with alpha
-    with Image.open(TEST_FILE_UNCOMPRESSED_RGB_WITH_ALPHA) as im:
+    with Image.open(test_file) as im:
         assert im.format == "DDS"
-        assert im.mode == "RGBA"
-        assert im.size == (800, 600)
+        assert im.mode == mode
+        assert im.size == size
 
-        assert_image_equal_tofile(
-            im, TEST_FILE_UNCOMPRESSED_RGB_WITH_ALPHA.replace(".dds", ".png")
-        )
+        assert_image_equal_tofile(im, test_file.replace(".dds", ".png"))
 
 
 def test__accept_true():
@@ -305,6 +305,8 @@ def test_save_unsupported_mode(tmp_path):
 @pytest.mark.parametrize(
     ("mode", "test_file"),
     [
+        ("L", "Tests/images/linear_gradient.png"),
+        ("LA", "Tests/images/uncompressed_la.png"),
         ("RGB", "Tests/images/hopper.png"),
         ("RGBA", "Tests/images/pil123rgba.png"),
     ],

docs/releasenotes/9.4.0.rst

@@ -70,7 +70,8 @@ TODO
 Other Changes
 =============
 
-TODO
-^^^^
+Added support for DDS L and LA images
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-TODO
+Support has been added to read and write L and LA DDS images in the uncompressed
+format, known as "luminance" textures.

src/PIL/DdsImagePlugin.py

@@ -135,11 +135,19 @@ def _open(self):
         fourcc = header.read(4)
         (bitcount,) = struct.unpack("<I", header.read(4))
         masks = struct.unpack("<4I", header.read(16))
-        if pfflags & DDPF_RGB:
+        if pfflags & DDPF_LUMINANCE:
+            # Texture contains uncompressed L or LA data
+            if pfflags & DDPF_ALPHAPIXELS:
+                self.mode = "LA"
+            else:
+                self.mode = "L"
+
+            self.tile = [("raw", (0, 0) + self.size, 0, (self.mode, 0, 1))]
+        elif pfflags & DDPF_RGB:
             # Texture contains uncompressed RGB data
             masks = {mask: ["R", "G", "B", "A"][i] for i, mask in enumerate(masks)}
             rawmode = ""
-            if bitcount == 32:
+            if pfflags & DDPF_ALPHAPIXELS:
                 rawmode += masks[0xFF000000]
             else:
                 self.mode = "RGB"
@@ -223,9 +231,24 @@ def load_seek(self, pos):
 
 
 def _save(im, fp, filename):
-    if im.mode not in ("RGB", "RGBA"):
+    if im.mode not in ("RGB", "RGBA", "L", "LA"):
         raise OSError(f"cannot write mode {im.mode} as DDS")
 
+    rawmode = im.mode
+    masks = [0xFF0000, 0xFF00, 0xFF]
+    if im.mode in ("L", "LA"):
+        pixel_flags = DDPF_LUMINANCE
+    else:
+        pixel_flags = DDPF_RGB
+        rawmode = rawmode[::-1]
+    if im.mode in ("LA", "RGBA"):
+        pixel_flags |= DDPF_ALPHAPIXELS
+        masks.append(0xFF000000)
+
+    bitcount = len(masks) * 8
+    while len(masks) < 4:
+        masks.append(0)
+
     fp.write(
         o32(DDS_MAGIC)
         + o32(124)  # header size
@@ -234,18 +257,15 @@ def _save(im, fp, filename):
         )  # flags
         + o32(im.height)
         + o32(im.width)
-        + o32((im.width * (32 if im.mode == "RGBA" else 24) + 7) // 8)  # pitch
+        + o32((im.width * bitcount + 7) // 8)  # pitch
         + o32(0)  # depth
         + o32(0)  # mipmaps
         + o32(0) * 11  # reserved
         + o32(32)  # pfsize
-        + o32(DDS_RGBA if im.mode == "RGBA" else DDPF_RGB)  # pfflags
+        + o32(pixel_flags)  # pfflags
         + o32(0)  # fourcc
-        + o32(32 if im.mode == "RGBA" else 24)  # bitcount
-        + o32(0xFF0000)  # rbitmask
-        + o32(0xFF00)  # gbitmask
-        + o32(0xFF)  # bbitmask
-        + o32(0xFF000000 if im.mode == "RGBA" else 0)  # abitmask
+        + o32(bitcount)  # bitcount
+        + b"".join(o32(mask) for mask in masks)  # rgbabitmask
         + o32(DDSCAPS_TEXTURE)  # dwCaps
         + o32(0)  # dwCaps2
         + o32(0)  # dwCaps3
@@ -255,7 +275,7 @@ def _save(im, fp, filename):
     if im.mode == "RGBA":
         r, g, b, a = im.split()
         im = Image.merge("RGBA", (a, r, g, b))
-    ImageFile._save(im, fp, [("raw", (0, 0) + im.size, 0, (im.mode[::-1], 0, 1))])
+    ImageFile._save(im, fp, [("raw", (0, 0) + im.size, 0, (rawmode, 0, 1))])
 
 
 def _accept(prefix):