Move barcode format plausibility checks out of decoding methods entirely

This puts the responsibility to call those entirely on the caller, which
allows us to special-case various PDF scenarios that would be filtered
out by running this unconditionally on the raster data.

autotests/barcodedecodertest.cpp

@@ -44,6 +44,7 @@ private Q_SLOTS:
 
         BarcodeDecoder decoder;
 #if HAVE_ZXING
+        QVERIFY(BarcodeDecoder::maybeBarcode(img.width(), img.height(), BarcodeDecoder::Any) & BarcodeDecoder::PDF417);
         QCOMPARE(decoder.decodeString(img, BarcodeDecoder::PDF417), QStringLiteral("PDF417 is a stacked linear barcode symbol format used in a variety of applications, primarily transport, identification cards, and inventory management."));
 #endif
     }
@@ -54,17 +55,20 @@ private Q_SLOTS:
         QVERIFY(!img.isNull());
         BarcodeDecoder decoder;
 #if HAVE_ZXING
+        QVERIFY(BarcodeDecoder::maybeBarcode(img.width(), img.height(), BarcodeDecoder::Any) & BarcodeDecoder::Aztec);
         QCOMPARE(decoder.decodeString(img, BarcodeDecoder::Aztec), QStringLiteral("This is an example Aztec symbol for Wikipedia."));
 #endif
         img.load(QStringLiteral(SOURCE_DIR "/barcodes/aztec-partial-quiet-zone.png"));
         QVERIFY(!img.isNull());
 #if HAVE_ZXING
+        QVERIFY(BarcodeDecoder::maybeBarcode(img.width(), img.height(), BarcodeDecoder::Any) & BarcodeDecoder::Aztec);
         QCOMPARE(decoder.decodeString(img, BarcodeDecoder::Aztec), QStringLiteral("KF5::Prison - The KDE barcode generation framework."));
 #endif
 
         img.load(QStringLiteral(SOURCE_DIR "/barcodes/uic918-3star.png"));
         QVERIFY(!img.isNull());
 #if HAVE_ZXING
+        QVERIFY(BarcodeDecoder::maybeBarcode(img.width(), img.height(), BarcodeDecoder::Any) & BarcodeDecoder::Aztec);
         const auto b = decoder.decodeBinary(img, BarcodeDecoder::Aztec);
         QCOMPARE(b.size(), 351);
         QVERIFY(b.startsWith("OTI010080000020"));
@@ -92,6 +96,7 @@ private Q_SLOTS:
 
         BarcodeDecoder decoder;
 #if HAVE_ZXING
+        QVERIFY(BarcodeDecoder::maybeBarcode(img.width(), img.height(), BarcodeDecoder::Any) & BarcodeDecoder::QRCode);
         QCOMPARE(decoder.decodeString(img, BarcodeDecoder::QRCode), result);
 #endif
 
@@ -112,22 +117,19 @@ private Q_SLOTS:
     void testNoCode()
     {
         BarcodeDecoder decoder;
-        QVERIFY(!decoder.isBarcode({}));
-        QCOMPARE(decoder.decodeBinary({}), QByteArray());
-        QCOMPARE(decoder.decodeString({}), QString());
+        QCOMPARE(decoder.decodeBinary({}, BarcodeDecoder::Any), QByteArray());
+        QCOMPARE(decoder.decodeString({}, BarcodeDecoder::Any), QString());
 
         QImage img(10, 10, QImage::Format_ARGB32);
         img.fill(Qt::black);
-        QVERIFY(!decoder.isBarcode(img));
-        QCOMPARE(decoder.decodeBinary(img), QByteArray());
-        QCOMPARE(decoder.decodeString(img), QString());
+        QCOMPARE(decoder.decodeBinary(img, BarcodeDecoder::Any), QByteArray());
+        QCOMPARE(decoder.decodeString(img, BarcodeDecoder::Any), QString());
 
         img = QImage(200, 200, QImage::Format_ARGB32);
         img.fill(Qt::red);
         img.fill(Qt::black);
-        QVERIFY(!decoder.isBarcode(img));
-        QCOMPARE(decoder.decodeBinary(img), QByteArray());
-        QCOMPARE(decoder.decodeString(img), QString());
+        QCOMPARE(decoder.decodeBinary(img, BarcodeDecoder::Any), QByteArray());
+        QCOMPARE(decoder.decodeString(img, BarcodeDecoder::Any), QString());
     }
 
     void testDecoderHints()
@@ -142,11 +144,11 @@ private Q_SLOTS:
         QCOMPARE(decoder.decodeString(img, BarcodeDecoder::QRCode), QString());
 
         decoder.clearCache();
-        QVERIFY(decoder.isBarcode(img));
-        QVERIFY(!decoder.isBarcode(img, BarcodeDecoder::PDF417));
-        QVERIFY(!decoder.isBarcode(img, BarcodeDecoder::QRCode));
-        QVERIFY(decoder.isBarcode(img, BarcodeDecoder::Aztec));
-        QVERIFY(decoder.isBarcode(img, BarcodeDecoder::AnySquare));
+        QCOMPARE(decoder.decodeString(img, BarcodeDecoder::Any), QStringLiteral("This is an example Aztec symbol for Wikipedia."));
+        QCOMPARE(decoder.decodeString(img, BarcodeDecoder::PDF417), QString());
+        QCOMPARE(decoder.decodeString(img, BarcodeDecoder::QRCode), QString());
+        QCOMPARE(decoder.decodeString(img, BarcodeDecoder::Aztec), QStringLiteral("This is an example Aztec symbol for Wikipedia."));
+        QCOMPARE(decoder.decodeString(img, BarcodeDecoder::AnySquare), QStringLiteral("This is an example Aztec symbol for Wikipedia."));
 #endif
     }
 

src/lib/barcodedecoder.cpp

@@ -45,28 +45,9 @@ static constexpr const auto ANY1D_MIN_ASPECT = 6.0f;
 BarcodeDecoder::BarcodeDecoder() = default;
 BarcodeDecoder::~BarcodeDecoder() = default;
 
-bool BarcodeDecoder::isBarcode(const QImage &img, BarcodeDecoder::BarcodeTypes hint) const
-{
-    if ((hint & IgnoreAspectRatio) == 0) {
-        hint = maybeBarcode(img.width(), img.height(), hint);
-    }
-
-    if (hint == None) {
-        return false;
-    }
-
-    auto &result = m_cache[img.cacheKey()];
-    decodeIfNeeded(img, hint, result);
-    return hint & result.positive;
-}
-
 QByteArray BarcodeDecoder::decodeBinary(const QImage &img, BarcodeDecoder::BarcodeTypes hint) const
 {
-    if ((hint & IgnoreAspectRatio) == 0) {
-        hint = maybeBarcode(img.width(), img.height(), hint);
-    }
-
-    if (hint == None) {
+    if (hint == None || img.isNull()) {
         return {};
     }
 
@@ -81,11 +62,7 @@ QByteArray BarcodeDecoder::decodeBinary(const QImage &img, BarcodeDecoder::Barco
 
 QString BarcodeDecoder::decodeString(const QImage &img, BarcodeDecoder::BarcodeTypes hint) const
 {
-    if ((hint & IgnoreAspectRatio) == 0) {
-        hint = maybeBarcode(img.width(), img.height(), hint);
-    }
-
-    if (hint == None) {
+    if (hint == None || img.isNull()) {
         return {};
     }
 

src/lib/barcodedecoder.h

@@ -50,14 +50,17 @@ public:
     };
     Q_DECLARE_FLAGS(BarcodeTypes, BarcodeType)
 
-    /** Checks if @p img contains a barcode of type @p hint. */
-    bool isBarcode(const QImage &img, BarcodeTypes hint = Any2D) const;
-
-    /** Decodes a binary payload barcode in @p img of type @p hint. */
-    QByteArray decodeBinary(const QImage &img, BarcodeTypes hint = Any2D) const;
+    /** Decodes a binary payload barcode in @p img of type @p hint.
+     *  @param hint has to be validated by something of the likes of maybeBarcode()
+     *  before.
+     */
+    QByteArray decodeBinary(const QImage &img, BarcodeTypes hint) const;
 
-    /** Decodes a textual payload barcode in @p img of type @p hint. */
-    QString decodeString(const QImage &img, BarcodeTypes hint = Any2D) const;
+    /** Decodes a textual payload barcode in @p img of type @p hint.
+     *  @param hint has to be validated by something of the likes of maybeBarcode()
+     *  before.
+     */
+    QString decodeString(const QImage &img, BarcodeTypes hint) const;
 
     /** Clears the internal cache. */
     void clearCache();