diff --git a/src/QR.cpp b/src/QR.cpp
index 4512691..608e2cf 100644
--- a/src/QR.cpp
+++ b/src/QR.cpp
@@ -1,6 +1,6 @@
 #include <iostream>
 #include <vector>
-#include <assert.h>
+#include <cassert>
 
 #include "QR.hpp"
 
diff --git a/src/QR.hpp b/src/QR.hpp
index d2ed8c9..ed90cf1 100644
--- a/src/QR.hpp
+++ b/src/QR.hpp
@@ -28,6 +28,10 @@ namespace massivedynamic {
 			std::unordered_map<Format, std::unique_ptr<Renderer>> renderers;
 		public:
 			QR(const std::string& data, std::string outputFile, size_t size, qrcodegen::QrCode::Ecc type);
+			QR(const QR&&)  = delete;
+			QR(QR&)         = delete;
+			~QR()           = default;
+
 			void render(Format format);
 	};
 
diff --git a/src/Renderer.hpp b/src/Renderer.hpp
index b91e954..4f968ec 100644
--- a/src/Renderer.hpp
+++ b/src/Renderer.hpp
@@ -11,7 +11,10 @@ class Renderer {
 		size_t targetSize;
 	public:
 		Renderer(const std::vector<bool>& pixels, size_t sourceSize, size_t targetSize) : pixels(pixels), sourceSize(sourceSize), targetSize(targetSize) {}
-		virtual ~Renderer() = default;
+		Renderer(const Renderer&&) = delete;
+		Renderer(Renderer&)        = delete;
+		virtual ~Renderer()        = default;
+
 		virtual void render(const std::string& filename) = 0;
 };
 
diff --git a/src/renderers/PixelRenderer.hpp b/src/renderers/PixelRenderer.hpp
index 8ffd810..e8e1179 100644
--- a/src/renderers/PixelRenderer.hpp
+++ b/src/renderers/PixelRenderer.hpp
@@ -2,6 +2,7 @@
 
 #include <math.h>
 #include <iostream>
+#include <cassert>
 
 #include "Renderer.hpp"
 #define STB_IMAGE_WRITE_IMPLEMENTATION
@@ -19,10 +20,7 @@ namespace massivedynamic {
 			void drawPixelScaled(size_t x, size_t y, Color color) {
 				size_t pixelSize = this->pixelSize;
 
-				if (pixelSize < 1) {
-					std::cerr << "ERROR: output file size is too small" << std::endl;
-					exit(1);
-				}
+				assert(pixelSize > 1 && "ERROR: output file size is too small");
 
 				size_t absoluteX = pixelSize * x + this->border;
 				size_t absoluteY = pixelSize * y + this->border;
@@ -42,12 +40,12 @@ namespace massivedynamic {
 			PixelRenderer(const std::vector<bool>& pixels, size_t sourceSize, size_t targetSize) : Renderer(pixels, sourceSize, targetSize), pixelSize(0) {
 				this->targetSize = this->targetSize == 0 ? (sourceSize + 2) * 2 : this->targetSize;
 				this->pixelSize  = round(static_cast<float>(this->targetSize) / static_cast<float>(this->sourceSize + 2));
-				this->border     = round((this->targetSize - this->pixelSize * this->sourceSize) / 2);
+				this->border     = round(static_cast<float>(this->targetSize - this->pixelSize * this->sourceSize) / 2.0f);
 
 				this->bitmap = std::vector<Color>(this->targetSize * this->targetSize, Colors::WHITE);
 			}
 
-			void generateBuffer() {
+			virtual void generateBuffer() {
 				for (size_t y = 0; y < sourceSize; y++) {
 					for (size_t x = 0; x < sourceSize; x++) {
 						if (!pixels.at(y * sourceSize + x))