QR-Code-scanner: integrate QUIRC library, implement QrDecoder, drop ZBar

src/QR-Code-scanner/Decoder.h

@@ -0,0 +1,21 @@
+#include <QImage>
+
+struct quirc;
+
+class QrDecoder
+{
+public:
+    QrDecoder(const QrDecoder &) = delete;
+    QrDecoder &operator=(const QrDecoder &) = delete;
+
+    QrDecoder();
+    ~QrDecoder();
+
+    std::vector<std::string> decode(const QImage &image);
+
+private:
+    std::vector<std::string> decodeGrayscale8(const QImage &image);
+
+private:
+    quirc *m_qr;
+};