Add alpha flag to DXT1a files.

src/nvimage/ColorBlock.cpp

@@ -62,7 +62,7 @@ void ColorBlock::init(const Image * img, uint x, uint y)
 	nvDebugCheck(bw != 0);
 	nvDebugCheck(bh != 0);
 
-	static int remainder[] = {
+	static const int remainder[] = {
 		0, 0, 0, 0,
 		0, 1, 0, 1,
 		0, 1, 2, 0,

src/nvimage/DirectDrawSurface.cpp

@@ -681,10 +681,17 @@ void DDSHeader::setPixelFormat(uint bitcount, uint rmask, uint gmask, uint bmask
 	nvCheck((gmask & amask) == 0);
 	nvCheck((bmask & amask) == 0);
 
-	this->pf.flags = DDPF_RGB;
-
-	if (amask != 0) {
-		this->pf.flags |= DDPF_ALPHAPIXELS;
+	if (rmask != 0 || gmask != 0 || bmask != 0)
+	{
+		this->pf.flags = DDPF_RGB;
+		
+		if (amask != 0) {
+			this->pf.flags |= DDPF_ALPHAPIXELS;
+		}
+	}
+	else if (amask != 0)
+	{
+		this->pf.flags |= DDPF_ALPHA;
 	}
 
 	if (bitcount == 0)
@@ -726,6 +733,12 @@ void DDSHeader::setNormalFlag(bool b)
 	else this->pf.flags &= ~DDPF_NORMAL;
 }
 
+void DDSHeader::setHasAlphaFlag(bool b)
+{
+	if (b) this->pf.flags |= DDPF_ALPHAPIXELS;
+	else this->pf.flags &= ~DDPF_ALPHAPIXELS;
+}
+
 void DDSHeader::swapBytes()
 {
 	this->fourcc = POSH_LittleU32(this->fourcc);
@@ -883,7 +896,7 @@ bool DirectDrawSurface::hasAlpha() const
 {
 	if (header.hasDX10Header())
 	{
-		// @@ TODO: Update with all formats.
+#pragma message(NV_FILE_LINE "Update hasAlpha to handle all DX10 formats.")
 		return 
 			header.header10.dxgiFormat == DXGI_FORMAT_BC1_UNORM ||
 			header.header10.dxgiFormat == DXGI_FORMAT_BC2_UNORM ||
@@ -906,6 +919,7 @@ bool DirectDrawSurface::hasAlpha() const
 			}
 			else
 			{
+				// @@ Here we could check the ALPHA_PIXELS flag, but nobody sets it.
 				return true;
 			}
 		}
@@ -991,6 +1005,13 @@ void DirectDrawSurface::setNormalFlag(bool b)
 	header.setNormalFlag(b);
 }
 
+void DirectDrawSurface::setHasAlphaFlag(bool b)
+{
+	nvDebugCheck(isValid());
+	header.setHasAlphaFlag(b);
+}
+
+
 void DirectDrawSurface::mipmap(Image * img, uint face, uint mipmap)
 {
 	nvDebugCheck(isValid());

src/nvimage/DirectDrawSurface.h

@@ -98,6 +98,7 @@ namespace nv
 		void setPixelFormat(uint bitcount, uint rmask, uint gmask, uint bmask, uint amask);
 		void setDX10Format(uint format);
 		void setNormalFlag(bool b);
+		void setHasAlphaFlag(bool b);
 		
 		void swapBytes();
 		
@@ -130,6 +131,7 @@ namespace nv
 		bool isTextureCube() const;
 
 		void setNormalFlag(bool b);
+		void setHasAlphaFlag(bool b);
 		
 		void mipmap(Image * img, uint f, uint m);
 		//	void mipmap(FloatImage * img, uint f, uint m);

src/nvtt/Context.cpp

@@ -414,6 +414,7 @@ bool Compressor::Private::outputHeader(const InputOptions::Private & inputOption
 			{
 				if (compressionOptions.format == Format_DXT1 || compressionOptions.format == Format_DXT1a || compressionOptions.format == Format_DXT1n) {
 					header.setDX10Format(71);
+					if (compressionOptions.format == Format_DXT1a) header.setHasAlphaFlag(true);
 					if (inputOptions.isNormalMap) header.setNormalFlag(true);
 				}
 				else if (compressionOptions.format == Format_DXT3) {