Added BC5_UNORM reading

Tests/test_file_dds.py

@@ -10,6 +10,7 @@
 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_DX10_BC5 = "Tests/images/bc5.dds"
 TEST_FILE_DX10_BC7 = "Tests/images/bc7-argb-8bpp_MipMaps-1.dds"
 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"
@@ -58,6 +59,19 @@ def test_sanity_dxt3():
         assert_image_equal_tofile(im, TEST_FILE_DXT3.replace(".dds", ".png"))
 
 
+def test_dx10_bc5():
+    """Check DX10 images can be opened"""
+
+    with Image.open(TEST_FILE_DX10_BC5) as im:
+        im.load()
+
+        assert im.format == "DDS"
+        assert im.mode == "RGB"
+        assert im.size == (540, 676)
+
+        assert_image_equal_tofile(im, TEST_FILE_DX10_BC5.replace(".dds", ".png"))
+
+
 def test_dx10_bc7():
     """Check DX10 images can be opened"""
 

src/PIL/DdsImagePlugin.py

@@ -97,6 +97,7 @@
 DXGI_FORMAT_R8G8B8A8_TYPELESS = 27
 DXGI_FORMAT_R8G8B8A8_UNORM = 28
 DXGI_FORMAT_R8G8B8A8_UNORM_SRGB = 29
+DXGI_FORMAT_BC5_UNORM = 83
 DXGI_FORMAT_BC7_TYPELESS = 97
 DXGI_FORMAT_BC7_UNORM = 98
 DXGI_FORMAT_BC7_UNORM_SRGB = 99
@@ -155,7 +156,11 @@ def _open(self):
                 # ignoring flags which pertain to volume textures and cubemaps
                 dxt10 = BytesIO(self.fp.read(20))
                 dxgi_format, dimension = struct.unpack("<II", dxt10.read(8))
-                if dxgi_format in (DXGI_FORMAT_BC7_TYPELESS, DXGI_FORMAT_BC7_UNORM):
+                if dxgi_format == DXGI_FORMAT_BC5_UNORM:
+                    self.pixel_format = "BC5"
+                    n = 5
+                    self.mode = "RGB"
+                elif dxgi_format in (DXGI_FORMAT_BC7_TYPELESS, DXGI_FORMAT_BC7_UNORM):
                     self.pixel_format = "BC7"
                     n = 7
                 elif dxgi_format == DXGI_FORMAT_BC7_UNORM_SRGB:

src/decode.c

@@ -368,13 +368,15 @@ PyImaging_BcnDecoderNew(PyObject *self, PyObject *args) {
         case 1: /* BC1: 565 color, 1-bit alpha */
         case 2: /* BC2: 565 color, 4-bit alpha */
         case 3: /* BC3: 565 color, 2-endpoint 8-bit interpolated alpha */
-        case 5: /* BC5: 2-channel 8-bit via 2 BC3 alpha blocks */
         case 7: /* BC7: 4-channel 8-bit via everything */
             actual = "RGBA";
             break;
         case 4: /* BC4: 1-channel 8-bit via 1 BC3 alpha block */
             actual = "L";
             break;
+        case 5: /* BC5: 2-channel 8-bit via 2 BC3 alpha blocks */
+            actual = "RGB";
+            break;
         case 6: /* BC6: 3-channel 16-bit float */
             /* TODO: support 4-channel floating point images */
             actual = "RGBAF";