Add interface to specify color transformations.

src/nvtt/InputOptions.cpp

@@ -83,6 +83,9 @@ void InputOptions::reset()
 	m.inputGamma = 2.2f;
 	m.outputGamma = 2.2f;
 	
+	m.colorTransform = ColorTransform_None;
+	m.linearTransform = Matrix(identity);
+
 	m.generateMipmaps = false;
 	m.maxLevel = -1;
 	m.mipmapFilter = MipmapFilter_Box;
@@ -258,3 +261,18 @@ void InputOptions::setNormalizeMipmaps(bool normalize)
 {
 	m.normalizeMipmaps = normalize;
 }
+
+/// Set color transform.
+void InputOptions::setColorTransform(ColorTransform t)
+{
+	m.colorTransform = t;
+}
+
+// Set linear transform for the given channel.
+void InputOptions::setLinearTransfrom(int channel, float w0, float w1, float w2, float w3)
+{
+	nvCheck(channel >= 0 && channel < 4);
+
+	Vector4 w(w0, w1, w2, w3);
+	//m.linearTransform.setRow(channel, w);
+}

src/nvtt/InputOptions.h

@@ -26,6 +26,7 @@
 
 #include <nvcore/Ptr.h>
 #include <nvmath/Vector.h>
+#include <nvmath/Matrix.h>
 #include <nvimage/Image.h>
 #include "nvtt.h"
 
@@ -58,7 +59,11 @@ namespace nvtt
 		// Gamma conversion.
 		float inputGamma;
 		float outputGamma;
-		
+	
+		// Color transform.
+		ColorTransform colorTransform;
+		nv::Matrix linearTransform;
+
 		// Mipmap generation options.
 		bool generateMipmaps;
 		int maxLevel;
@@ -73,6 +78,7 @@ namespace nvtt
 
 		// Cone map options.
 		bool convertToConeMap;
+
 	};
 
 	// Internal image structure.

src/nvtt/nvtt.cpp

@@ -459,6 +459,14 @@ bool nvtt::compress(const InputOptions & inputOptions, const OutputOptions & out
 				img = toFixedImage(floatImage.ptr(), inputOptions.m);
 			}
 			
+			// @@ Where to do the color transform?
+			// - Color transform may not be linear, so we cannot do before computing mipmaps.
+			// - Should be done in linear space, that is, after gamma correction.
+
+			// @@ Error! gamma correction is not performed when mipmap data provied.
+
+			// @@ This code is too complicated, too prone to erros, and hard to understand. Must be simplified!
+
 			quantize(img, inputOptions.m, format);
 			
 			compressMipmap(img, outputOptions, compressionOptions.m);

src/nvtt/nvtt.h

@@ -139,7 +139,13 @@ namespace nvtt
 		MipmapFilter_Kaiser,	///< Kaiser-windowed Sinc filter is the best downsampling filter.
 	};
 	
-
+	enum ColorTransform
+	{
+		ColorTransform_None,
+		ColorTransform_Linear,
+		ColorTransform_CoYCg,
+		ColorTransform_CoSCgY,
+	};
 
 	/// Input options. Specify format and layout of the input texture.
 	struct InputOptions
@@ -179,6 +185,10 @@ namespace nvtt
 		NVTT_API void setNormalFilter(float small, float medium, float big, float large);
 		NVTT_API void setNormalizeMipmaps(bool b);
 
+		// Set color transforms.
+		NVTT_API void setColorTransform(ColorTransform t);
+		NVTT_API void setLinearTransfrom(int channel, float w0, float w1, float w2, float w3);
+
 	//private:
 		struct Private;
 		Private & m;