From 8c5d5c7e6b597cef2b5a39417ddc457f91015f9f Mon Sep 17 00:00:00 2001
From: Sam Bourne <sambvfx@gmail.com>
Date: Mon, 4 Dec 2023 09:54:10 -0800
Subject: [PATCH 1/3] Add support for BC4 dds files

---
 Tests/images/bc4_unorm.dds | Bin 0 -> 2892 bytes
 Tests/test_file_dds.py     |  12 ++++++++++++
 src/PIL/DdsImagePlugin.py  |   8 +++++++-
 3 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 Tests/images/bc4_unorm.dds

diff --git a/Tests/images/bc4_unorm.dds b/Tests/images/bc4_unorm.dds
new file mode 100644
index 0000000000000000000000000000000000000000..13da711bd13d456406188b445a9668c40fc8604e
GIT binary patch
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diff --git a/Tests/test_file_dds.py b/Tests/test_file_dds.py
index bb9af7967b7..85a3ae172b9 100644
--- a/Tests/test_file_dds.py
+++ b/Tests/test_file_dds.py
@@ -12,6 +12,7 @@
 TEST_FILE_DXT5 = "Tests/images/dxt5-argb-8bbp-interpolatedalpha_MipMaps-1.dds"
 TEST_FILE_ATI1 = "Tests/images/ati1.dds"
 TEST_FILE_ATI2 = "Tests/images/ati2.dds"
+TEST_FILE_DX10_BC4_UNORM = "Tests/images/bc4_unorm.dds"
 TEST_FILE_DX10_BC5_TYPELESS = "Tests/images/bc5_typeless.dds"
 TEST_FILE_DX10_BC5_UNORM = "Tests/images/bc5_unorm.dds"
 TEST_FILE_DX10_BC5_SNORM = "Tests/images/bc5_snorm.dds"
@@ -82,6 +83,17 @@ def test_sanity_ati1():
         assert_image_equal_tofile(im, TEST_FILE_ATI1.replace(".dds", ".png"))
 
 
+def test_dx10_bc4():
+    """Check DX10 BC4 images can be opened"""
+
+    with Image.open(TEST_FILE_DX10_BC4_UNORM) as im:
+        im.load()
+
+        assert im.format == "DDS"
+        assert im.mode == "L"
+        assert im.size == (64, 64)
+
+
 @pytest.mark.parametrize(
     "image_path",
     (
diff --git a/src/PIL/DdsImagePlugin.py b/src/PIL/DdsImagePlugin.py
index 54f358c7f9a..faf6a4e436c 100644
--- a/src/PIL/DdsImagePlugin.py
+++ b/src/PIL/DdsImagePlugin.py
@@ -98,6 +98,8 @@
 DXGI_FORMAT_R8G8B8A8_TYPELESS = 27
 DXGI_FORMAT_R8G8B8A8_UNORM = 28
 DXGI_FORMAT_R8G8B8A8_UNORM_SRGB = 29
+DXGI_FORMAT_BC4_TYPELESS = 79
+DXGI_FORMAT_BC4_UNORM = 80
 DXGI_FORMAT_BC5_TYPELESS = 82
 DXGI_FORMAT_BC5_UNORM = 83
 DXGI_FORMAT_BC5_SNORM = 84
@@ -190,7 +192,11 @@ def _open(self):
                 # ignoring flags which pertain to volume textures and cubemaps
                 (dxgi_format,) = struct.unpack("<I", self.fp.read(4))
                 self.fp.read(16)
-                if dxgi_format in (DXGI_FORMAT_BC5_TYPELESS, DXGI_FORMAT_BC5_UNORM):
+                if dxgi_format in (DXGI_FORMAT_BC4_TYPELESS, DXGI_FORMAT_BC4_UNORM):
+                    self.pixel_format = "BC4"
+                    n = 4
+                    self._mode = "L"
+                elif dxgi_format in (DXGI_FORMAT_BC5_TYPELESS, DXGI_FORMAT_BC5_UNORM):
                     self.pixel_format = "BC5"
                     n = 5
                     self._mode = "RGB"

From c1b3c3467882c3af0cd510ac4bc202a35ef7e04f Mon Sep 17 00:00:00 2001
From: Andrew Murray <radarhere@users.noreply.github.com>
Date: Tue, 5 Dec 2023 07:18:07 +1100
Subject: [PATCH 2/3] Added expected test image

---
 Tests/images/bc4_unorm.png | Bin 0 -> 982 bytes
 Tests/test_file_dds.py     |   2 ++
 2 files changed, 2 insertions(+)
 create mode 100644 Tests/images/bc4_unorm.png

diff --git a/Tests/images/bc4_unorm.png b/Tests/images/bc4_unorm.png
new file mode 100644
index 0000000000000000000000000000000000000000..71d536c8453b16874c3ce777555fbbfb55667b60
GIT binary patch
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literal 0
HcmV?d00001

diff --git a/Tests/test_file_dds.py b/Tests/test_file_dds.py
index 85a3ae172b9..337f541f6a6 100644
--- a/Tests/test_file_dds.py
+++ b/Tests/test_file_dds.py
@@ -93,6 +93,8 @@ def test_dx10_bc4():
         assert im.mode == "L"
         assert im.size == (64, 64)
 
+        assert_image_equal_tofile(im, TEST_FILE_DX10_BC4_UNORM.replace(".dds", ".png"))
+
 
 @pytest.mark.parametrize(
     "image_path",

From 0e36c14680a2023d5f1e5ab118d48bbeb4c9ba31 Mon Sep 17 00:00:00 2001
From: Andrew Murray <radarhere@users.noreply.github.com>
Date: Tue, 5 Dec 2023 07:39:15 +1100
Subject: [PATCH 3/3] Added test BC4 TYPELESS image

---
 Tests/images/bc4_typeless.dds | Bin 0 -> 2892 bytes
 Tests/test_file_dds.py        |  13 +++++++++++--
 2 files changed, 11 insertions(+), 2 deletions(-)
 create mode 100644 Tests/images/bc4_typeless.dds

diff --git a/Tests/images/bc4_typeless.dds b/Tests/images/bc4_typeless.dds
new file mode 100644
index 0000000000000000000000000000000000000000..27f87889f43d5b5054f3971c412a594dc4dc161e
GIT binary patch
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literal 0
HcmV?d00001

diff --git a/Tests/test_file_dds.py b/Tests/test_file_dds.py
index 337f541f6a6..e9fb045887b 100644
--- a/Tests/test_file_dds.py
+++ b/Tests/test_file_dds.py
@@ -12,6 +12,7 @@
 TEST_FILE_DXT5 = "Tests/images/dxt5-argb-8bbp-interpolatedalpha_MipMaps-1.dds"
 TEST_FILE_ATI1 = "Tests/images/ati1.dds"
 TEST_FILE_ATI2 = "Tests/images/ati2.dds"
+TEST_FILE_DX10_BC4_TYPELESS = "Tests/images/bc4_typeless.dds"
 TEST_FILE_DX10_BC4_UNORM = "Tests/images/bc4_unorm.dds"
 TEST_FILE_DX10_BC5_TYPELESS = "Tests/images/bc5_typeless.dds"
 TEST_FILE_DX10_BC5_UNORM = "Tests/images/bc5_unorm.dds"
@@ -83,10 +84,18 @@ def test_sanity_ati1():
         assert_image_equal_tofile(im, TEST_FILE_ATI1.replace(".dds", ".png"))
 
 
-def test_dx10_bc4():
+@pytest.mark.parametrize(
+    "image_path",
+    (
+        TEST_FILE_DX10_BC4_UNORM,
+        # hexeditted to be typeless
+        TEST_FILE_DX10_BC4_TYPELESS,
+    ),
+)
+def test_dx10_bc4(image_path):
     """Check DX10 BC4 images can be opened"""
 
-    with Image.open(TEST_FILE_DX10_BC4_UNORM) as im:
+    with Image.open(image_path) as im:
         im.load()
 
         assert im.format == "DDS"