ABI/API: Restore InputOptions::setColorTransform(ColorTransform)

The only colortransform actually implemented was the transform from
RGB to YCoCG (ColorTransform_YCoCg).
Restore the full enum for API compatibility, and allow the transform
to be specified using InputOptions::setColortransform.

Fixes part of https://github.com/castano/nvidia-texture-tools/issues/259

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>

src/nvtt/Context.cpp

@@ -277,6 +277,11 @@ bool Compressor::Private::compress(const InputOptions::Private & inputOptions, c
             // Resize input.
             img.resize(w, h, d, ResizeFilter_Box);
 
+            // Apply color transform.
+            if (inputOptions.colorTransform == ColorTransform_YCoCg) {
+                img.toYCoCg();
+            }
+
             nvtt::Surface tmp = img;
             if (!img.isNormalMap()) {
                 tmp.toGamma(inputOptions.outputGamma);

src/nvtt/InputOptions.cpp

@@ -104,6 +104,8 @@ void InputOptions::reset()
     m.inputGamma = 2.2f;
     m.outputGamma = 2.2f;
 
+    m.colorTransform = ColorTransform_None;
+
     m.generateMipmaps = true;
     m.maxLevel = -1;
     m.mipmapFilter = MipmapFilter_Box;
@@ -337,6 +339,12 @@ 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.
 // Stub for ABI compatibily, never implemented
 void InputOptions::setLinearTransform(int, float, float, float, float)

src/nvtt/InputOptions.h

@@ -55,6 +55,9 @@ namespace nvtt
         float inputGamma;
         float outputGamma;
 
+        // Color transform.
+        ColorTransform colorTransform;
+
         // Mipmap generation options.
         bool generateMipmaps;
         int maxLevel;

src/nvtt/nvtt.h

@@ -249,6 +249,17 @@ namespace nvtt
         ResizeFilter_Mitchell,
     };
 
+    // Color transformation.
+    // deprecated since 2.1.0
+    enum ColorTransform
+    {
+        ColorTransform_None,
+        ColorTransform_Linear,
+        ColorTransform_Swizzle,
+        ColorTransform_YCoCg,
+        ColorTransform_ScaledYCoCg,
+    };
+
     // Extents rounding mode.
     enum RoundMode
     {
@@ -323,6 +334,7 @@ namespace nvtt
         NVTT_API void setNormalizeMipmaps(bool b);
 
         // Set color transforms.
+        NVTT_API void setColorTransform(ColorTransform t);
         NVTT_API void setLinearTransform(int channel, float w0, float w1, float w2, float w3);
 
         // Set resizing options.