From 325a2ac96d3e3924904acfeec7bde96f7fd38183 Mon Sep 17 00:00:00 2001
From: Pavel Krajcevski <pavel@cs.unc.edu>
Date: Mon, 26 Jan 2015 17:27:35 -0500
Subject: [PATCH] Add utility function for splitting images into images of
 pixel channels.

---
 Base/include/FasTC/Image.h |  5 ++++
 Base/src/Image.cpp         | 55 ++++++++++++++++++++++++++++++++++----
 Base/test/TestImage.cpp    | 44 ++++++++++++++++++++++++++++++
 3 files changed, 99 insertions(+), 5 deletions(-)

diff --git a/Base/include/FasTC/Image.h b/Base/include/FasTC/Image.h
index 6554604..b1ad2aa 100644
--- a/Base/include/FasTC/Image.h
+++ b/Base/include/FasTC/Image.h
@@ -125,6 +125,11 @@ namespace FasTC {
 
   extern void GenerateGaussianKernel(Image<IPixel> &out, uint32 size, float sigma);
 
+  template <typename PixelType>
+  extern void SplitChannels(const Image<PixelType> &in,
+                            Image<IPixel> *channelOne,
+                            Image<IPixel> *channelTwo,
+                            Image<IPixel> *channelThree);
 }  // namespace FasTC
 
 #endif // __TEXCOMP_IMAGE_H__
diff --git a/Base/src/Image.cpp b/Base/src/Image.cpp
index 681b97d..480273e 100644
--- a/Base/src/Image.cpp
+++ b/Base/src/Image.cpp
@@ -59,6 +59,11 @@ static inline T sad( const T &a, const T &b ) {
   return (a > b)? a - b : b - a;
 }
 
+template<typename T>
+static inline T Clamp(const T &v, const T &a, const T &b) {
+  return ::std::min(::std::max(a, v), b);
+}
+
 // wtf
 #ifdef _MSC_VER
 template<typename T> T log2(T x) { return static_cast<T>(log((long double)x) / log(2.0)); }
@@ -485,11 +490,6 @@ void Image<PixelType>::SetImageData(uint32 width, uint32 height, PixelType *data
   }
 }
 
-  template<typename T>
-  static inline T Clamp(const T &v, const T &a, const T &b) {
-    return ::std::min(::std::max(a, v), b);
-  }
-
 template<typename PixelType>
 void Image<PixelType>::Filter(const Image<IPixel> &kernel) {
   Image<IPixel> k(kernel);
@@ -565,4 +565,49 @@ void GenerateGaussianKernel(Image<IPixel> &out, uint32 size, float sigma) {
   }
 }
 
+template <typename T>
+void SplitChannelsImpl(const Image<T> &in,
+                       Image<IPixel> *channelOne,
+                       Image<IPixel> *channelTwo,
+                       Image<IPixel> *channelThree) {
+  assert(channelOne != NULL);
+  assert(channelTwo != NULL);
+  assert(channelThree != NULL);
+  assert(in.GetWidth() == channelOne->GetWidth());
+  assert(in.GetHeight() == channelOne->GetHeight());
+  assert(in.GetWidth() == channelTwo->GetWidth());
+  assert(in.GetHeight() == channelTwo->GetHeight());
+  assert(in.GetWidth() == channelThree->GetWidth());
+  assert(in.GetHeight() == channelThree->GetHeight());
+
+  Image<IPixel> &i1 = *channelOne;
+  Image<IPixel> &i2 = *channelTwo;
+  Image<IPixel> &i3 = *channelThree;
+
+  for (uint32 j = 0; j < in.GetHeight(); j++) {
+    for(uint32 i = 0; i < in.GetWidth(); i++) {
+      T c = in(i, j);
+      i1(i, j) = c.R();
+      i2(i, j) = c.G();
+      i3(i, j) = c.B();
+    }
+  }
+}
+
+template <>
+void SplitChannels<Color>(const Image<Color> &in,
+                          Image<IPixel> *channelOne,
+                          Image<IPixel> *channelTwo,
+                          Image<IPixel> *channelThree) {
+  SplitChannelsImpl(in, channelOne, channelTwo, channelThree);
+}
+
+template <>
+void SplitChannels<Pixel>(const Image<Pixel> &in,
+                          Image<IPixel> *channelOne,
+                          Image<IPixel> *channelTwo,
+                          Image<IPixel> *channelThree) {
+  SplitChannelsImpl(in, channelOne, channelTwo, channelThree);
+}
+
 }  // namespace FasTC
diff --git a/Base/test/TestImage.cpp b/Base/test/TestImage.cpp
index a874a31..3890a4a 100644
--- a/Base/test/TestImage.cpp
+++ b/Base/test/TestImage.cpp
@@ -51,6 +51,7 @@
  */
 
 #include "gtest/gtest.h"
+#include "FasTC/Color.h"
 #include "FasTC/Image.h"
 #include "FasTC/IPixel.h"
 #include "FasTC/Pixel.h"
@@ -167,3 +168,46 @@ TEST(Image, ComputeMSSIM) {
   double SSIM = img.ComputeSSIM(&img);
   EXPECT_EQ(SSIM, 1.0);
 }
+
+TEST(Image, SplitImage) {
+
+  const uint32 w = 16;
+  const uint32 h = 16;
+
+  FasTC::Image<FasTC::Pixel> img(w, h);
+  for(uint32 j = 0; j < h; j++) {
+    for(uint32 i = 0; i < w; i++) {
+      img(i, j) = FasTC::Pixel(i, j, i+j, 255);
+    }
+  }
+
+  FasTC::Image<FasTC::IPixel> i1(w, h);
+  FasTC::Image<FasTC::IPixel> i2(w, h);
+  FasTC::Image<FasTC::IPixel> i3(w, h);
+  FasTC::SplitChannels(img, &i1, &i2, &i3);
+
+  for(uint32 j = 0; j < h; j++) {
+    for(uint32 i = 0; i < w; i++) {
+      EXPECT_EQ(i1(i, j), img(i, j).R());
+      EXPECT_EQ(i2(i, j), img(i, j).G());
+      EXPECT_EQ(i3(i, j), img(i, j).B());
+    }
+  }
+
+  FasTC::Image<FasTC::Color> img2(w, h);
+  for(uint32 j = 0; j < h; j++) {
+    for(uint32 i = 0; i < w; i++) {
+      img2(i, j) = FasTC::Color(j, i, i*j, 255);
+    }
+  }
+
+  FasTC::SplitChannels(img2, &i1, &i2, &i3);
+
+  for(uint32 j = 0; j < h; j++) {
+    for(uint32 i = 0; i < w; i++) {
+      EXPECT_EQ(i1(i, j), img2(i, j).R());
+      EXPECT_EQ(i2(i, j), img2(i, j).G());
+      EXPECT_EQ(i3(i, j), img2(i, j).B());
+    }
+  }
+}