Update DDS alpha mode metadata

- Make alpha mode 3 bits instead of 2
- Rename 4TH_CHANNEL to CUSTOM
- Reorder enum

DDSTextureLoader/DDSTextureLoader.cpp

@@ -103,7 +103,7 @@ struct DDS_PIXELFORMAT
 
 enum DDS_MISC_FLAGS2
 {
-    DDS_MISC_FLAGS2_ALPHA_MODE_MASK = 0x3L,
+    DDS_MISC_FLAGS2_ALPHA_MODE_MASK = 0x7L,
 };
 
 typedef struct
@@ -1329,7 +1329,15 @@ static DDS_ALPHA_MODE GetAlphaMode( _In_ const DDS_HEADER* header )
         if ( MAKEFOURCC( 'D', 'X', '1', '0' ) == header->ddspf.fourCC )
         {
             auto d3d10ext = reinterpret_cast<const DDS_HEADER_DXT10*>( (const char*)header + sizeof(DDS_HEADER) );
-            return static_cast<DDS_ALPHA_MODE>(d3d10ext->miscFlags2 & DDS_MISC_FLAGS2_ALPHA_MODE_MASK);
+            auto mode = static_cast<DDS_ALPHA_MODE>( d3d10ext->miscFlags2 & DDS_MISC_FLAGS2_ALPHA_MODE_MASK );
+            switch( mode )
+            {
+            case DDS_ALPHA_MODE_STRAIGHT:
+            case DDS_ALPHA_MODE_PREMULTIPLIED:
+            case DDS_ALPHA_MODE_OPAQUE:
+            case DDS_ALPHA_MODE_CUSTOM:
+                return mode;
+            }
         }
         else if ( ( MAKEFOURCC( 'D', 'X', 'T', '2' ) == header->ddspf.fourCC )
                   || ( MAKEFOURCC( 'D', 'X', 'T', '4' ) == header->ddspf.fourCC ) )
@@ -1338,7 +1346,7 @@ static DDS_ALPHA_MODE GetAlphaMode( _In_ const DDS_HEADER* header )
         }
     }
 
-    return DDS_ALPHA_MODE_STRAIGHT;
+    return DDS_ALPHA_MODE_UNKNOWN;
 }
 
 
@@ -1379,6 +1387,10 @@ HRESULT DirectX::CreateDDSTextureFromMemoryEx( ID3D11Device* d3dDevice,
     {
         *textureView = nullptr;
     }
+    if ( alphaMode )
+    {
+        *alphaMode = DDS_ALPHA_MODE_UNKNOWN;
+    }
 
     if (!d3dDevice || !ddsData || (!texture && !textureView))
     {
@@ -1482,6 +1494,10 @@ HRESULT DirectX::CreateDDSTextureFromFileEx( ID3D11Device* d3dDevice,
     {
         *textureView = nullptr;
     }
+    if ( alphaMode )
+    {
+        *alphaMode = DDS_ALPHA_MODE_UNKNOWN;
+    }
 
     if (!d3dDevice || !fileName || (!texture && !textureView))
     {

DDSTextureLoader/DDSTextureLoader.h

@@ -44,10 +44,11 @@ namespace DirectX
 {
     enum DDS_ALPHA_MODE
     {
-        DDS_ALPHA_MODE_STRAIGHT      = 0,
+        DDS_ALPHA_MODE_UNKNOWN       = 0,
-        DDS_ALPHA_MODE_PREMULTIPLIED = 1,
+        DDS_ALPHA_MODE_STRAIGHT      = 1,
-        DDS_ALPHA_MODE_4TH_CHANNEL   = 2,
+        DDS_ALPHA_MODE_PREMULTIPLIED = 2,
         DDS_ALPHA_MODE_OPAQUE        = 3,
+        DDS_ALPHA_MODE_CUSTOM        = 4,
     };
 
     HRESULT CreateDDSTextureFromMemory( _In_ ID3D11Device* d3dDevice,

DirectXTex/DDS.h

@@ -184,15 +184,16 @@ enum DDS_RESOURCE_MISC_FLAG
 
 enum DDS_MISC_FLAGS2
 {
-    DDS_MISC_FLAGS2_ALPHA_MODE_MASK = 0x3L,
+    DDS_MISC_FLAGS2_ALPHA_MODE_MASK = 0x7L,
 };
 
 enum DDS_ALPHA_MODE
 {
-    DDS_ALPHA_MODE_STRAIGHT      = 0,
+    DDS_ALPHA_MODE_UNKNOWN       = 0,
-    DDS_ALPHA_MODE_PREMULTIPLIED = 1,
+    DDS_ALPHA_MODE_STRAIGHT      = 1,
-    DDS_ALPHA_MODE_4TH_CHANNEL   = 2,
+    DDS_ALPHA_MODE_PREMULTIPLIED = 2,
     DDS_ALPHA_MODE_OPAQUE        = 3,
+    DDS_ALPHA_MODE_CUSTOM        = 4,
 };
 
 struct DDS_HEADER

DirectXTex/DirectXTex.h

@@ -101,16 +101,17 @@ namespace DirectX
 
     enum TEX_MISC_FLAG2
     {
-        TEX_MISC2_ALPHA_MODE_MASK = 0x3L,
+        TEX_MISC2_ALPHA_MODE_MASK = 0x7L,
     };
 
     enum TEX_ALPHA_MODE
         // Matches DDS_ALPHA_MODE, encoded in MISC_FLAGS2
     {
-        TEX_ALPHA_MODE_STRAIGHT      = 0,
+        TEX_ALPHA_MODE_UNKNOWN       = 0,
-        TEX_ALPHA_MODE_PREMULTIPLIED = 1,
+        TEX_ALPHA_MODE_STRAIGHT      = 1,
-        TEX_ALPHA_MODE_4TH_CHANNEL   = 2,
+        TEX_ALPHA_MODE_PREMULTIPLIED = 2,
         TEX_ALPHA_MODE_OPAQUE        = 3,
+        TEX_ALPHA_MODE_CUSTOM        = 4,
     };
 
     struct TexMetadata

DirectXTex/DirectXTexDDS.cpp

@@ -315,10 +315,11 @@ static HRESULT _DecodeDDSHeader( _In_reads_bytes_(size) LPCVOID pSource, size_t
 
         static_assert( TEX_MISC2_ALPHA_MODE_MASK == DDS_MISC_FLAGS2_ALPHA_MODE_MASK, "DDS header mismatch");
 
+        static_assert( TEX_ALPHA_MODE_UNKNOWN == DDS_ALPHA_MODE_UNKNOWN, "DDS header mismatch");
         static_assert( TEX_ALPHA_MODE_STRAIGHT == DDS_ALPHA_MODE_STRAIGHT, "DDS header mismatch");
         static_assert( TEX_ALPHA_MODE_PREMULTIPLIED == DDS_ALPHA_MODE_PREMULTIPLIED, "DDS header mismatch");
-        static_assert( TEX_ALPHA_MODE_4TH_CHANNEL == DDS_ALPHA_MODE_4TH_CHANNEL, "DDS header mismatch");
         static_assert( TEX_ALPHA_MODE_OPAQUE == DDS_ALPHA_MODE_OPAQUE, "DDS header mismatch");
+        static_assert( TEX_ALPHA_MODE_CUSTOM == DDS_ALPHA_MODE_CUSTOM, "DDS header mismatch");
 
         metadata.miscFlags2 = d3d10ext->miscFlags2;
     }
@@ -637,10 +638,11 @@ HRESULT _EncodeDDSHeader( const TexMetadata& metadata, DWORD flags,
 
         static_assert( TEX_MISC2_ALPHA_MODE_MASK == DDS_MISC_FLAGS2_ALPHA_MODE_MASK, "DDS header mismatch");
 
+        static_assert( TEX_ALPHA_MODE_UNKNOWN == DDS_ALPHA_MODE_UNKNOWN, "DDS header mismatch");
         static_assert( TEX_ALPHA_MODE_STRAIGHT == DDS_ALPHA_MODE_STRAIGHT, "DDS header mismatch");
         static_assert( TEX_ALPHA_MODE_PREMULTIPLIED == DDS_ALPHA_MODE_PREMULTIPLIED, "DDS header mismatch");
-        static_assert( TEX_ALPHA_MODE_4TH_CHANNEL == DDS_ALPHA_MODE_4TH_CHANNEL, "DDS header mismatch");
         static_assert( TEX_ALPHA_MODE_OPAQUE == DDS_ALPHA_MODE_OPAQUE, "DDS header mismatch");
+        static_assert( TEX_ALPHA_MODE_CUSTOM == DDS_ALPHA_MODE_CUSTOM, "DDS header mismatch");
 
         if ( flags & DDS_FLAGS_FORCE_DX10_EXT_MISC2 )
         {

Texconv/texconv.cpp

@@ -1080,7 +1080,11 @@ int __cdecl wmain(_In_ int argc, _In_z_count_(argc) wchar_t* argv[])
             }
             else if ( dwOptions & (1 << OPT_SEPALPHA) )
             {
-                info.SetAlphaMode(TEX_ALPHA_MODE_4TH_CHANNEL);
+                info.SetAlphaMode(TEX_ALPHA_MODE_CUSTOM);
+            }
+            else
+            {
+                info.SetAlphaMode(TEX_ALPHA_MODE_STRAIGHT);
             }
         }
         else