diff --git a/color.cc b/color.cc
index 7d2aea5..b3b52e2 100644
--- a/color.cc
+++ b/color.cc
@@ -2,3 +2,39 @@
 
 RgbColor::RgbColor(const Color<3>& src)
     : Color<3>(src) {}
+
+RgbColor::operator HsvColor() const {
+  constexpr int32_t kSection = kNumColors / 6;
+  int32_t max = *std::max_element(this->begin(), this->end());
+  int32_t min = *std::min_element(this->begin(), this->end());
+  int32_t delta = max - min;
+
+  if (delta == 0) {
+    return {{{{{0x0000, 0x0000, max}}}}};
+  }
+
+  HsvColor ret = {{{{{0, 0, max}}}}};
+
+  if (max == this->at(0)) {
+    ret.at(0) = (kSection * (this->at(1) - this->at(2))) / delta + (0 * kSection);
+  } else if (max == this->at(1)) {
+    ret.at(0) = (kSection * (this->at(2) - this->at(0))) / delta + (2 * kSection);
+  } else {
+    assert(max == this->at(2));
+    ret.at(0) = (kSection * (this->at(0) - this->at(1))) / delta + (4 * kSection);
+  }
+
+  if (ret.at(0) < 0) {
+    ret.at(0) += kNumColors;
+  }
+
+  if (max > 0) {
+    ret.at(1) = static_cast<int32_t>(static_cast<int64_t>(delta) * kMaxColor / max);
+  }
+
+  return ret;
+}
+
+
+HsvColor::HsvColor(const Color<3>& src)
+    : Color<3>(src) {}
diff --git a/color.h b/color.h
index c0d874c..0d88099 100644
--- a/color.h
+++ b/color.h
@@ -9,6 +9,7 @@
 
 constexpr int32_t kMinColor = 0;
 constexpr int32_t kMaxColor = UINT16_MAX;
+constexpr int32_t kNumColors = (kMaxColor - kMinColor) + 1;
 
 class ColorBase {};
 
@@ -20,10 +21,21 @@ struct Color : public Array<int32_t, C>, public ColorBase {
 };
 
 
+struct RgbColor;
+struct HsvColor;
+
+
 struct RgbColor : public Color<3> {
- public:
   RgbColor() = default;
   RgbColor(const Color<3>& src);
+
+  operator HsvColor() const;
+};
+
+
+struct HsvColor : public Color<3> {
+  HsvColor() = default;
+  HsvColor(const Color<3>& src);
 };
 
 
@@ -58,7 +70,7 @@ template <int32_t C>
 std::ostream& operator<<(std::ostream& os, const Color<C>& color) {
   os << std::hex << std::setfill('0') << "Color(";
   for (int32_t c = 0; c < C; ++c) {
-    os << "0x" << std::setw(4) << color.at(0);
+    os << "0x" << std::setw(4) << color.at(c);
     if (c < C - 1) {
       os << ", ";
     }
diff --git a/image.h b/image.h
index 3e97693..7888a00 100644
--- a/image.h
+++ b/image.h
@@ -13,8 +13,7 @@ class ImageBase {};
 
 
 template <class C>
-class ImageColorBase : public ImageBase {
- public:
+struct ImageColorBase : public ImageBase {
   ImageColorBase() = default;
   ImageColorBase(const ImageColorBase<C>&) = default;
   virtual ~ImageColorBase() = default;