Added support for reading ATI1/ATI2 (BC4/BC5) DDS images

Tests/test_file_dds.py

@@ -10,6 +10,8 @@
 TEST_FILE_DXT1 = "Tests/images/dxt1-rgb-4bbp-noalpha_MipMaps-1.dds"
 TEST_FILE_DXT3 = "Tests/images/dxt3-argb-8bbp-explicitalpha_MipMaps-1.dds"
 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_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"
@@ -62,6 +64,32 @@ def test_sanity_dxt5():
     assert_image_equal_tofile(im, TEST_FILE_DXT5.replace(".dds", ".png"))
 
 
+def test_sanity_ati1():
+    """Check ATI1 images can be opened"""
+
+    with Image.open(TEST_FILE_ATI1) as im:
+        im.load()
+
+        assert im.format == "DDS"
+        assert im.mode == "L"
+        assert im.size == (64, 64)
+
+        assert_image_equal_tofile(im, TEST_FILE_ATI1.replace(".dds", ".png"))
+
+
+def test_sanity_ati2():
+    """Check ATI2 images can be opened"""
+
+    with Image.open(TEST_FILE_ATI2) as im:
+        im.load()
+
+        assert im.format == "DDS"
+        assert im.mode == "RGB"
+        assert im.size == (256, 256)
+
+        assert_image_equal_tofile(im, TEST_FILE_DX10_BC5_UNORM.replace(".dds", ".png"))
+
+
 @pytest.mark.parametrize(
     ("image_path", "expected_path"),
     (

src/PIL/DdsImagePlugin.py

@@ -156,6 +156,14 @@ def _open(self):
             elif fourcc == b"DXT5":
                 self.pixel_format = "DXT5"
                 n = 3
+            elif fourcc == b"ATI1":
+                self.pixel_format = "BC4"
+                n = 4
+                self.mode = "L"
+            elif fourcc == b"ATI2":
+                self.pixel_format = "BC5"
+                n = 5
+                self.mode = "RGB"
             elif fourcc == b"BC5S":
                 self.pixel_format = "BC5S"
                 n = 5