Introduced new option for QZXing. if QZXing::setTryHarder is set to true, if the image decoding fails, the image will be rotated and will be tested against angles 90o, 180o, 270o. This increased the success rate for the Qr codes.

Plus, minor changes at the handling of failed decoding in QZXing.

src/QZXing.h

@@ -75,6 +75,8 @@ public:
     }
 #endif
 
+    void setTryHarder(bool tryHarder);
+    bool getTryHarder();
     static QString decoderFormatToString(int fmt);
     QString foundedFormat() const;
     QString charSet() const;
@@ -166,6 +168,7 @@ private:
     int processingTime;
     QString foundedFmt;
     QString charSet_;
+    bool tryHarder_;
 
     /**
       * If true, the decoding operation will take place at a different thread.

src/qzxing.cpp

@@ -15,7 +15,7 @@
 
 using namespace zxing;
 
-QZXing::QZXing(QObject *parent) : QObject(parent)
+QZXing::QZXing(QObject *parent) : QObject(parent), tryHarder_(false)
 {
     decoder = new MultiFormatReader();
     /*setDecoder(DecoderFormat_QR_CODE |
@@ -48,6 +48,16 @@ QZXing::QZXing(QZXing::DecoderFormat decodeHints, QObject *parent) : QObject(par
     setDecoder(decodeHints);
 }
 
+void QZXing::setTryHarder(bool tryHarder)
+{
+    tryHarder_ = tryHarder;
+}
+
+bool QZXing::getTryHarder()
+{
+    return tryHarder_;
+}
+
 QString QZXing::decoderFormatToString(int fmt)
 {
     switch (fmt) {
@@ -196,6 +206,7 @@ QString QZXing::decodeImage(const QImage &image, int maxWidth, int maxHeight, bo
     else
         ciw = CameraImageWrapper::Factory(image, 999, 999, true);
 
+    QString errorMessage = "Unknown";
     try {
         Ref<LuminanceSource> imageRef(ciw);
         Ref<GlobalHistogramBinarizer> binz( new GlobalHistogramBinarizer(imageRef) );
@@ -214,11 +225,11 @@ QString QZXing::decodeImage(const QImage &image, int maxWidth, int maxHeight, bo
             hints.setTryHarder(true);
 
             try {
-              res = decoder->decode(bb, hints);
-              hasSucceded = true;
+                res = decoder->decode(bb, hints);
+                hasSucceded = true;
             } catch(zxing::Exception &e) {}
 
-            if (bb->isRotateSupported()) {
+            if (tryHarder_ && bb->isRotateSupported()) {
                 Ref<BinaryBitmap> bbTmp = bb;
 
                 for (int i=0; (i<3 && !hasSucceded); i++) {
@@ -233,30 +244,34 @@ QString QZXing::decodeImage(const QImage &image, int maxWidth, int maxHeight, bo
             }
         }
 
-        QString string = QString(res->getText()->getText().c_str());
-        if (!string.isEmpty() && (string.length() > 0)) {
-            int fmt = res->getBarcodeFormat().value;
-            foundedFmt = decoderFormatToString(fmt);
-            charSet_ = QString::fromStdString(res->getCharSet());
-            if (!charSet_.isEmpty()) {
-                QTextCodec *codec = QTextCodec::codecForName(res->getCharSet().c_str());
-                if (codec)
-                    string = codec->toUnicode(res->getText()->getText().c_str());
+        if (hasSucceded) {
+            QString string = QString(res->getText()->getText().c_str());
+            if (!string.isEmpty() && (string.length() > 0)) {
+                int fmt = res->getBarcodeFormat().value;
+                foundedFmt = decoderFormatToString(fmt);
+                charSet_ = QString::fromStdString(res->getCharSet());
+                if (!charSet_.isEmpty()) {
+                    QTextCodec *codec = QTextCodec::codecForName(res->getCharSet().c_str());
+                    if (codec)
+                        string = codec->toUnicode(res->getText()->getText().c_str());
+                }
+                emit tagFound(string);
+                emit tagFoundAdvanced(string, foundedFmt, charSet_);
             }
-            emit tagFound(string);
-            emit tagFoundAdvanced(string, foundedFmt, charSet_);
+            processingTime = t.elapsed();
+            emit decodingFinished(true);
+            return string;
         }
-        processingTime = t.elapsed();
-        emit decodingFinished(true);
-        return string;
     }
     catch(zxing::Exception &e)
     {
-        emit error(QString(e.what()));
-        emit decodingFinished(false);
-        processingTime = t.elapsed();
-        return "";
+        errorMessage = QString(e.what());
     }
+
+    emit error(errorMessage);
+    emit decodingFinished(false);
+    processingTime = t.elapsed();
+    return "";
 }
 
 QString QZXing::decodeImageFromFile(const QString& imageFilePath, int maxWidth, int maxHeight, bool smoothTransformation)
@@ -335,7 +350,7 @@ QImage QZXing::encodeData(const QString& data)
                                    qRgb(255,255,255));
 
         image = image.scaled(240, 240);
-//        bool success =  image.save("tmp.bmp","BMP");
+        //        bool success =  image.save("tmp.bmp","BMP");
     } catch (std::exception& e) {
         std::cout << "Error: " << e.what() << std::endl;
     }

tests/src/QZXingTests/DecodeValidator.cpp

@@ -13,6 +13,7 @@
 DecodeValidator::DecodeValidator() : decoder(), decoderCorrelationMap(), testResults()
 {
     initializeDecoderCorrelation();
+    decoder.setTryHarder(true);
 }
 
 void DecodeValidator::initializeDecoderCorrelation()