diff --git a/colorchecker.h b/colorchecker.h
index eec63ec..9967e04 100644
--- a/colorchecker.h
+++ b/colorchecker.h
@@ -74,20 +74,15 @@ int32_t ScoreLut(const Image<X, Y, RgbColor>& image, const LutBase& lut) {
   Array<int32_t, kColorCheckerSrgb.size()> diff;
   diff.fill(INT32_MAX);
 
-  for (int32_t y = 0; y < Y; ++y) {
-    const auto& row = image.at(y);
-
-    for (int32_t x = 0; x < X; ++x) {
-      const auto pixel = lut.MapColor(row.at(x));
-
-      for (int32_t cc = 0; cc < kColorCheckerSrgb.ssize(); ++cc) {
-        auto pixel_diff = pixel.AbsDiff(kColorCheckerSrgb.at(cc));
-        if (pixel_diff < diff.at(cc)) {
-          diff.at(cc) = pixel_diff;
-        }
+  image.ForEach([&diff, &lut](const RgbColor& color) {
+    const auto pixel = lut.MapColor(color);
+    for (int32_t cc = 0; cc < kColorCheckerSrgb.ssize(); ++cc) {
+      auto pixel_diff = pixel.AbsDiff(kColorCheckerSrgb.at(cc));
+      if (pixel_diff < diff.at(cc)) {
+        diff.at(cc) = pixel_diff;
       }
     }
-  }
+  });
 
   return std::accumulate(diff.begin(), diff.end(), 0);
 }
diff --git a/image.h b/image.h
index cfec073..3e97693 100644
--- a/image.h
+++ b/image.h
@@ -9,11 +9,27 @@
 #include "color.h"
 #include "coord.h"
 
+class ImageBase {};
+
+
+template <class C>
+class ImageColorBase : public ImageBase {
+ public:
+  ImageColorBase() = default;
+  ImageColorBase(const ImageColorBase<C>&) = default;
+  virtual ~ImageColorBase() = default;
+
+  virtual void ForEach(std::function<void(const C&)> callback) const = 0;
+};
+
+
 template <int32_t X, int32_t Y, class C>
-class Image : public Array<Array<C, X>, Y> {
+class Image : public Array<Array<C, X>, Y>, ImageColorBase<C> {
  public:
   constexpr const C& GetPixel(const Coord<2>& coord) const;
 
+  void ForEach(std::function<void(const C&)> callback) const override;
+
   void SetPixel(const Coord<2>& coord, const C& color);
   void DrawXLine(const Coord<2>& start, const C& color, int32_t length);
   void DrawYLine(const Coord<2>& start, const C& color, int32_t length);
@@ -28,6 +44,16 @@ constexpr const C& Image<X, Y, C>::GetPixel(const Coord<2>& coord) const {
   return this->at(coord.at(1)).at(coord.at(0));
 }
 
+template <int32_t X, int32_t Y, class C>
+void  Image<X, Y, C>::ForEach(std::function<void(const C&)> callback) const {
+  for (int32_t y = 0; y < Y; ++y) {
+    const auto& row = this->at(y);
+    for (int32_t x = 0; x < X; ++x) {
+      callback(row.at(x));
+    }
+  }
+}
+
 template <int32_t X, int32_t Y, class C>
 void Image<X, Y, C>::SetPixel(const Coord<2>& coord, const C& color) {
   if (coord.at(0) >= X || coord.at(1) >= Y) {