Force the DDS/DXT stream decompression.

The DDSCodec keeps the DXT format if the hardware supports it. However using this stack object it is possible to enforce the DXT decompression into RGB(A) format. This is useful e.g. when we have DDS texture without mipmaps and we need them. DirectX11 does not generate mipmaps if the texture is compressed (DirectX9 does it automatically).

Also added support to obtain the DDS stream (not only saving to file).

Author: CsabaX

OgreMain/src/OgreDDSCodec.cpp

@@ -159,6 +159,27 @@ namespace {
     const uint32 D3DFMT_A32B32G32R32F   = 116;
 }
 
+    //---------------------------------------------------------------------
+    // Force the DXT stream decompression
+    //---------------------------------------------------------------------
+    int DDSDecodeEnforcer::mCount = 0;
+
+    DDSDecodeEnforcer::DDSDecodeEnforcer()
+    {
+        ++mCount;
+    }
+
+    DDSDecodeEnforcer::~DDSDecodeEnforcer()
+    {
+        --mCount;
+        assert(mCount >= 0);
+    }
+
+    bool DDSDecodeEnforcer::isEnabled()
+    {
+        return mCount > 0;
+    }
+
     //---------------------------------------------------------------------
     DDSCodec* DDSCodec::msInstance = 0;
     //---------------------------------------------------------------------
@@ -193,7 +214,7 @@ namespace {
     { 
     }
     //---------------------------------------------------------------------
-    void DDSCodec::encodeToFile(const Any& input, const String& outFileName) const
+    DataStreamPtr DDSCodec::encode(const Any& input) const
     {
         Image* image = any_cast<Image*>(input);
 
@@ -402,21 +423,42 @@ namespace {
                 dataPtr = tmpData;
             }
 
-            try
-            {
-                // Write the file
-                std::ofstream of;
-                of.open(outFileName.c_str(), std::ios_base::binary|std::ios_base::out);
-                of.write((const char *)&ddsMagic, sizeof(uint32));
-                of.write((const char *)&ddsHeader, DDS_HEADER_SIZE);
-                // XXX flipEndian on each pixel chunk written unless isFloat32r ?
-                of.write(dataPtr, image->getSize());
-                of.close();
-            }
-            catch(...)
-            {
-            }
+            size_t totalSize = sizeof(uint32) + DDS_HEADER_SIZE + image->getSize();
+            auto pMemStream = OGRE_NEW Ogre::MemoryDataStream(totalSize);
+
+            pMemStream->write(&ddsMagic, sizeof(uint32));
+            pMemStream->write(&ddsHeader, DDS_HEADER_SIZE);
+            pMemStream->write(dataPtr, image->getSize());
+            pMemStream->seek(0);
+
             delete [] tmpData;
+
+            return Ogre::DataStreamPtr(pMemStream);
+        }
+    }
+    //---------------------------------------------------------------------
+    void DDSCodec::encodeToFile(const Any& input, const String& outFileName) const
+    {
+        DataStreamPtr strm = encode(input);
+
+        try
+        {
+            // Write the file
+            std::ofstream of;
+            of.open(outFileName.c_str(), std::ios_base::binary | std::ios_base::out);
+
+            const size_t buffSize = 4096;
+            char buffer[buffSize];
+
+            while (!strm->eof()) {
+                size_t bytesRead = strm->read(buffer, buffSize);
+                of.write(buffer, bytesRead);
+            }
+
+            of.close();
+        }
+        catch(...)
+        {
         }
     }
     //---------------------------------------------------------------------
@@ -824,7 +866,8 @@ namespace {
         if (PixelUtil::isCompressed(sourceFormat))
         {
             if (Root::getSingleton().getRenderSystem() == NULL ||
-                !Root::getSingleton().getRenderSystem()->getCapabilities()->hasCapability(RSC_TEXTURE_COMPRESSION_DXT))
+                !Root::getSingleton().getRenderSystem()->getCapabilities()->hasCapability(RSC_TEXTURE_COMPRESSION_DXT) ||
+                DDSDecodeEnforcer::isEnabled())
             {
                 // We'll need to decompress
                 decompressDXT = true;

OgreMain/src/OgreDDSCodec.h

@@ -44,6 +44,23 @@ namespace Ogre {
     struct DXTExplicitAlphaBlock;
     struct DXTInterpolatedAlphaBlock;
 
+    /** Force the DXT stream decompression.
+
+        The DDSCodec keeps the DXT format if the hardware supports it.
+        However this stack object can enforce the DXT decompression into RGB(A) format.
+    */
+    class _OgreExport DDSDecodeEnforcer
+    {
+    public:
+        DDSDecodeEnforcer();
+        ~DDSDecodeEnforcer();
+
+        static bool isEnabled();
+
+    private:
+        static int mCount;
+    };
+
     /** Codec specialized in loading DDS (Direct Draw Surface) images.
 
         We implement our own codec here since we need to be able to keep DXT
@@ -72,6 +89,7 @@ namespace Ogre {
         DDSCodec();
         virtual ~DDSCodec() { }
 
+        DataStreamPtr encode(const Any& input) const override;
         void encodeToFile(const Any& input, const String& outFileName) const override;
         void decode(const DataStreamPtr& input, const Any& output) const override;
         String magicNumberToFileExt(const char *magicNumberPtr, size_t maxbytes) const override;