diff --git a/src/BC1/BC1Decoder.cpp b/src/BC1/BC1Decoder.cpp
index 860c734..23e276a 100644
--- a/src/BC1/BC1Decoder.cpp
+++ b/src/BC1/BC1Decoder.cpp
@@ -33,7 +33,7 @@ void BC1Decoder::DecodeBlock(Color4x4 dest, BC1Block *const block) const noexcep
     const auto l = block->GetLowColor();
     const auto h = block->GetHighColor();
     const auto selectors = block->UnpackSelectors();
-    const auto colors = _interpolator.InterpolateBC1(l, h);
+    const auto colors = _interpolator->InterpolateBC1(l, h);
 
     for (unsigned y = 0; y < 4; y++) {
         for (unsigned x = 0; x < 4; x++) {
diff --git a/src/BC1/BC1Decoder.h b/src/BC1/BC1Decoder.h
index 741cd26..8defd16 100644
--- a/src/BC1/BC1Decoder.h
+++ b/src/BC1/BC1Decoder.h
@@ -19,24 +19,28 @@
 
 #pragma once
 
+#include <memory>
+
 #include "../BlockDecoder.h"
+#include "../ColorBlock.h"
 #include "../blocks.h"
 #include "../interpolator.h"
 #include "../ndebug.h"
-#include "../ColorBlock.h"
 
 namespace rgbcx {
 class BC1Decoder final : public BlockDecoder<BC1Block, 4, 4> {
    public:
-    BC1Decoder(const Interpolator &interpolator = Interpolator(), bool write_alpha = false) : _interpolator(interpolator), _write_alpha(write_alpha) {}
+    using InterpolatorPtr = std::shared_ptr<Interpolator>;
+    BC1Decoder(const InterpolatorPtr interpolator = std::make_shared<Interpolator>(), bool write_alpha = false)
+        : _interpolator(interpolator), _write_alpha(write_alpha) {}
 
     void DecodeBlock(Color4x4 dest, BC1Block *const block) const noexcept(ndebug) override;
 
-    constexpr const Interpolator &GetInterpolator() const { return _interpolator; }
+    InterpolatorPtr GetInterpolator() const { return _interpolator; }
     constexpr bool WritesAlpha() const { return _write_alpha; }
 
    private:
-    const Interpolator &_interpolator;
+    const InterpolatorPtr _interpolator;
     const bool _write_alpha;
 };
 }  // namespace rgbcx
diff --git a/src/BC3/BC3Decoder.cpp b/src/BC3/BC3Decoder.cpp
index c343eb6..6c3d423 100644
--- a/src/BC3/BC3Decoder.cpp
+++ b/src/BC3/BC3Decoder.cpp
@@ -28,7 +28,7 @@
 namespace rgbcx {
 
 void BC3Decoder::DecodeBlock(Color4x4 dest, BC3Block *const block) const noexcept(ndebug) {
-    _bc1_decoder.DecodeBlock(dest, &(block->color_block));
-    _bc4_decoder.DecodeBlock(dest, &(block->alpha_block), 3);
+    _bc1_decoder->DecodeBlock(dest, &(block->color_block));
+    _bc4_decoder->DecodeBlock(dest, &(block->alpha_block), 3);
 }
 }  // namespace rgbcx
\ No newline at end of file
diff --git a/src/BC3/BC3Decoder.h b/src/BC3/BC3Decoder.h
index 1520fc7..f913148 100644
--- a/src/BC3/BC3Decoder.h
+++ b/src/BC3/BC3Decoder.h
@@ -19,6 +19,8 @@
 
 #pragma once
 
+#include <memory>
+
 #include "../BC1/BC1Decoder.h"
 #include "../BC4/BC4Decoder.h"
 #include "../BlockDecoder.h"
@@ -30,13 +32,17 @@
 namespace rgbcx {
 class BC3Decoder : public BlockDecoder<BC3Block, 4, 4> {
    public:
-    BC3Decoder(const Interpolator &interpolator = Interpolator()) : BC3Decoder(BC1Decoder(interpolator, false)) {}
-    BC3Decoder(const BC1Decoder &bc1_decoder, const BC4Decoder &bc4_decoder = BC4Decoder()) : _bc1_decoder(bc1_decoder), _bc4_decoder(bc4_decoder) {}
+    using InterpolatorPtr = std::shared_ptr<Interpolator>;
+    using BC1DecoderPtr = std::shared_ptr<BC1Decoder>;
+    using BC4DecoderPtr = std::shared_ptr<BC4Decoder>;
+
+    BC3Decoder(InterpolatorPtr interpolator = std::make_shared<Interpolator>()) : BC3Decoder(std::make_shared<BC1Decoder>(interpolator)) {}
+    BC3Decoder(BC1DecoderPtr bc1_decoder, BC4DecoderPtr bc4_decoder = std::make_shared<BC4Decoder>()) : _bc1_decoder(bc1_decoder), _bc4_decoder(bc4_decoder) {}
 
     void DecodeBlock(Color4x4 dest, BC3Block *const block) const noexcept(ndebug) override;
 
    private:
-    const BC1Decoder &_bc1_decoder;
-    const BC4Decoder &_bc4_decoder;
+    const BC1DecoderPtr _bc1_decoder;
+    const BC4DecoderPtr _bc4_decoder;
 };
 }  // namespace rgbcx
diff --git a/src/BC5/BC5Decoder.cpp b/src/BC5/BC5Decoder.cpp
index 75310d5..22aa723 100644
--- a/src/BC5/BC5Decoder.cpp
+++ b/src/BC5/BC5Decoder.cpp
@@ -27,7 +27,7 @@
 namespace rgbcx {
 
 void BC5Decoder::DecodeBlock(Color4x4 dest, BC5Block *const block) const noexcept(ndebug) {
-    _bc4_decoder.DecodeBlock(dest, &block->chan0_block, _chan0);
-    _bc4_decoder.DecodeBlock(dest, &block->chan1_block, _chan1);
+    _bc4_decoder->DecodeBlock(dest, &block->chan0_block, _chan0);
+    _bc4_decoder->DecodeBlock(dest, &block->chan1_block, _chan1);
 }
 }  // namespace rgbcx
\ No newline at end of file
diff --git a/src/BC5/BC5Decoder.h b/src/BC5/BC5Decoder.h
index 7da6579..675c515 100644
--- a/src/BC5/BC5Decoder.h
+++ b/src/BC5/BC5Decoder.h
@@ -20,18 +20,21 @@
 #pragma once
 
 #include <stddef.h>
+#include <memory>
 
 #include "../BC4/BC4Decoder.h"
 #include "../BlockDecoder.h"
 #include "../ColorBlock.h"
-#include "../ndebug.h"
 #include "../blocks.h"
+#include "../ndebug.h"
 
 namespace rgbcx {
 class BC5Decoder : public BlockDecoder<BC5Block, 4, 4> {
    public:
-    BC5Decoder(size_t chan0 = 0, size_t chan1 = 1) : BC5Decoder(BC4Decoder(), chan0, chan1) {}
-    BC5Decoder(const BC4Decoder &bc4_decoder, size_t chan0 = 0, size_t chan1 = 1) : _bc4_decoder(bc4_decoder), _chan0(chan0), _chan1(chan1) {}
+    using BC4DecoderPtr = std::shared_ptr<BC4Decoder>;
+
+    BC5Decoder(size_t chan0 = 0, size_t chan1 = 1) : BC5Decoder(std::make_shared<BC4Decoder>(), chan0, chan1) {}
+    BC5Decoder(BC4DecoderPtr bc4_decoder, size_t chan0 = 0, size_t chan1 = 1) : _bc4_decoder(bc4_decoder), _chan0(chan0), _chan1(chan1) {}
 
     void DecodeBlock(Color4x4 dest, BC5Block *const block) const noexcept(ndebug) override;
 
@@ -39,7 +42,7 @@ class BC5Decoder : public BlockDecoder<BC5Block, 4, 4> {
     constexpr size_t GetChannel1() const { return _chan1; }
 
    private:
-    const BC4Decoder &_bc4_decoder;
+    const BC4DecoderPtr _bc4_decoder;
     const size_t _chan0;
     const size_t _chan1;
 };
diff --git a/src/Color.h b/src/Color.h
index 1ffa8a4..6544633 100644
--- a/src/Color.h
+++ b/src/Color.h
@@ -56,7 +56,7 @@ class Color {
     void SetRGBA(const Color &other) { SetRGBA(other.r, other.g, other.b, other.a); }
 
     void SetRGB(uint8_t vr, uint8_t vg, uint8_t vb);
-    void SetRGB(const Color &other) { SetRGB(other.r, other.g, other.a); }
+    void SetRGB(const Color &other) { SetRGB(other.r, other.g, other.b); }
 
     uint16_t pack565();
     uint16_t pack565Unscaled();
@@ -67,6 +67,6 @@ class Color {
     static Color min(const Color &A, const Color &B);
     static Color max(const Color &A, const Color &B);
 
-    unsigned get_luma() const { return (13938U * r + 46869U * g + 4729U * b + 32768U) >> 16U; }  // REC709 weightings
+    int get_luma() const { return (13938U * r + 46869U * g + 4729U * b + 32768U) >> 16U; }  // REC709 weightings
 };
 #pragma pack(pop)
\ No newline at end of file
diff --git a/src/test/test.cpp b/src/test/test.cpp
index 3c5a749..dd560d4 100644
--- a/src/test/test.cpp
+++ b/src/test/test.cpp
@@ -264,9 +264,11 @@ class image_metrics {
                 const color_quad_u8 &ca = a(x, y);
                 const color_quad_u8 &cb = b(x, y);
 
-                if (!num_channels)
-                    hist[iabs(ca.get_luma() - cb.get_luma())]++;
-                else {
+                if (!num_channels) {
+//                    int luma_diff = ;
+                    unsigned index = iabs(ca.get_luma() - cb.get_luma());
+                    hist[index]++;
+                } else {
                     for (uint32_t c = 0; c < num_channels; c++) hist[iabs(ca[first_channel + c] - cb[first_channel + c])]++;
                 }
             }
diff --git a/src/util.h b/src/util.h
index 438bec2..3c6d495 100644
--- a/src/util.h
+++ b/src/util.h
@@ -38,6 +38,7 @@ template <typename S> constexpr void Assert6Bit(S x) {
 }
 
 template <typename S> constexpr auto iabs(S i) {
+    static_assert(!std::is_unsigned<S>::value);
     using O = typename std::make_unsigned<S>::type;
     return (i < 0) ? static_cast<O>(-i) : static_cast<O>(i);
 }