Add vertical flip.

src/nvimage/FloatImage.cpp

@@ -941,6 +941,25 @@ void FloatImage::applyKernelHorizontal(const PolyphaseKernel & k, int y, uint c,
 	}
 }
 
+
+// Vertical flip in place.
+void FloatImage::flip()
+{
+    const uint w = m_width;
+    const uint h = m_height;
+    const uint h2 = h / 2;
+
+    for (uint c = 0; c < m_componentNum; c++) {
+        for (uint y = 0; y < h2; y++) {
+            float * src = scanline(y, c);
+            float * dst = scanline(h - 1 - y, c);
+            for (uint x = 0; x < w; x++) {
+                swap(src[x], dst[x]);
+            }
+        }
+    }
+}
+
 FloatImage* FloatImage::clone() const
 {
 	FloatImage* copy = new FloatImage();

src/nvimage/FloatImage.h

@@ -77,7 +77,6 @@ public:
 	NVIMAGE_API FloatImage * resize(const Filter & filter, uint w, uint h, WrapMode wm) const;
 
 	NVIMAGE_API FloatImage * resize(const Filter & filter, uint w, uint h, WrapMode wm, uint alpha) const;
-	//@}
 
 	NVIMAGE_API float applyKernel(const Kernel2 * k, int x, int y, uint c, WrapMode wm) const;
 	NVIMAGE_API float applyKernelVertical(const Kernel1 * k, int x, int y, uint c, WrapMode wm) const;
@@ -87,6 +86,8 @@ public:
 	NVIMAGE_API void applyKernelVertical(const PolyphaseKernel & k, int x, uint c, uint a, WrapMode wm, float * output) const;
 	NVIMAGE_API void applyKernelHorizontal(const PolyphaseKernel & k, int y, uint c, uint a, WrapMode wm, float * output) const;
 
+    NVIMAGE_API void flip();
+	//@}
 	
 	uint width() const { return m_width; }
 	uint height() const { return m_height; }

src/nvtt/TexImage.cpp

@@ -1086,3 +1086,14 @@ float TexImage::rootMeanSquaredError_alpha(const TexImage & reference) const
 	return float(sqrt(mse / totalCount));
 }
 
+void TexImage::flipVertically() {
+
+    detach();
+
+	foreach (i, m->imageArray)
+	{
+		if (m->imageArray[i] == NULL) continue;
+
+        m->imageArray[i]->flip();
+	}
+}

src/nvtt/nvtt.h

@@ -447,6 +447,9 @@ namespace nvtt
 		NVTT_API float rootMeanSquaredError_rgb(const TexImage & reference) const;
 		NVTT_API float rootMeanSquaredError_alpha(const TexImage & reference) const;
 
+        // Geometric transforms.
+        NVTT_API void flipVertically();
+
 	private:
 		void detach();