Check for single color blocks in all compressors.

ChangeLog

@@ -4,6 +4,10 @@ NVIDIA Texture Tools version 2.1.0
  * Support alpha premultiplication by Charles Nicholson. See issue 30.
  * Improved decompressor tool submitted by Amorilia. See issue 41.
 
+NVIDIA Texture Tools version 2.0.3
+ * More accurate DXT3 compressor. Fixes issue 38.
+ * Remove legacy compressors. Fix issue 34?
+
 NVIDIA Texture Tools version 2.0.2
  * Fix copy ctor error reported by Richard Sim.
  * Fix indexMirror error reported by Chris Lambert.

src/nvimage/ColorBlock.cpp

@@ -114,9 +114,12 @@ void ColorBlock::splatY()
 /// Returns true if the block has a single color.
 bool ColorBlock::isSingleColor() const
 {
-	for(int i = 1; i < 16; i++)
+	Color32 mask(0xFF, 0xFF, 0xFF, 0x00);
+	uint u = m_color[0].u & mask.u;
+	
+	for (int i = 1; i < 16; i++)
 	{
-		if (m_color[0] != m_color[i])
+		if (u != (m_color[i].u & mask.u))
 		{
 			return false;
 		}
@@ -134,10 +137,13 @@ bool ColorBlock::isSingleColorNoAlpha() const
 	{
 		if (m_color[i].a != 0) c = m_color[i];
 	}
-	
+
+	Color32 mask(0xFF, 0xFF, 0xFF, 0x00);
+	uint u = c.u & mask.u;
+
 	for(; i < 16; i++)
 	{
-		if (c != m_color[i])
+		if (u != (m_color[i].u & mask.u))
 		{
 			return false;
 		}

src/nvtt/CompressDXT.cpp

@@ -237,7 +237,16 @@ void nv::compressDXT1a(const Image * image, const OutputOptions::Private & outpu
 			
 			rgba.init(image, x, y);
 			
-			if (rgba.isSingleColor())
+			bool anyAlpha = false;
+			bool allAlpha = true;
+			
+			for (uint i = 0; i < 16; i++)
+			{
+				if (rgba.color(i).a < 128) anyAlpha = true;
+				else allAlpha = false;
+			}
+			
+			if ((!anyAlpha && rgba.isSingleColor() || allAlpha))
 			{
 				OptimalCompress::compressDXT1a(rgba.color(0), &block);
 			}
@@ -274,11 +283,18 @@ void nv::compressDXT3(const Image * image, const OutputOptions::Private & output
 			
 			// Compress explicit alpha.
 			OptimalCompress::compressDXT3A(rgba, &block.alpha);
-			
+
 			// Compress color.
-			squish::ColourSet colours((uint8 *)rgba.colors(), squish::kWeightColourByAlpha);
+			if (rgba.isSingleColor())
-			fit.SetColourSet(&colours, 0);
+			{
-			fit.Compress(&block.color);
+				OptimalCompress::compressDXT1(rgba.color(0), &block.color);
+			}
+			else
+			{
+				squish::ColourSet colours((uint8 *)rgba.colors(), squish::kWeightColourByAlpha);
+				fit.SetColourSet(&colours, 0);
+				fit.Compress(&block.color);
+			}
 			
 			if (outputOptions.outputHandler != NULL) {
 				outputOptions.outputHandler->writeData(&block, sizeof(block));
@@ -314,9 +330,16 @@ void nv::compressDXT5(const Image * image, const OutputOptions::Private & output
 			}
 
 			// Compress color.
-			squish::ColourSet colours((uint8 *)rgba.colors(), squish::kWeightColourByAlpha);
+			if (rgba.isSingleColor())
-			fit.SetColourSet(&colours, 0);
+			{
-			fit.Compress(&block.color);
+				OptimalCompress::compressDXT1(rgba.color(0), &block.color);
+			}
+			else
+			{
+				squish::ColourSet colours((uint8 *)rgba.colors(), squish::kWeightColourByAlpha);
+				fit.SetColourSet(&colours, 0);
+				fit.Compress(&block.color);
+			}
 			
 			if (outputOptions.outputHandler != NULL) {
 				outputOptions.outputHandler->writeData(&block, sizeof(block));

src/nvtt/QuickCompressDXT.cpp

@@ -481,7 +481,17 @@ void QuickCompress::compressDXT1(const ColorBlock & rgba, BlockDXT1 * dxtBlock)
 
 void QuickCompress::compressDXT1a(const ColorBlock & rgba, BlockDXT1 * dxtBlock)
 {
-	if (!rgba.hasAlpha())
+	bool hasAlpha = false;
+	
+	for (uint i = 0; i < 16; i++)
+	{
+		if (rgba.color(i).a < 128) {
+			hasAlpha = true;
+			break;
+		}
+	}
+	
+	if (!hasAlpha)
 	{
 		compressDXT1(rgba, dxtBlock);
 	}