Rotate images according to Exif orientation

Task-number: QTBUG-37946
Change-Id: I181f88acdff0ef76aa02e968dc6afca1ed495f38
Reviewed-by: aavit <eirik.aavitsland@digia.com>

src/gui/image/qjpeghandler.cpp

@@ -726,7 +726,7 @@ public:
     };
 
     QJpegHandlerPrivate(QJpegHandler *qq)
-        : quality(75), iod_src(0), state(Ready), q(qq)
+        : quality(75), exifOrientation(1), iod_src(0), state(Ready), q(qq)
     {}
 
     ~QJpegHandlerPrivate()
@@ -741,8 +741,10 @@ public:
 
     bool readJpegHeader(QIODevice*);
     bool read(QImage *image);
+    void applyExifOrientation(QImage *image);
 
     int quality;
+    int exifOrientation;
     QVariant size;
     QImage::Format format;
     QSize scaledSize;
@@ -760,6 +762,97 @@ public:
     QJpegHandler *q;
 };
 
+static bool readExifHeader(QDataStream &stream)
+{
+    char prefix[6];
+    if (stream.readRawData(prefix, sizeof(prefix)) != sizeof(prefix))
+        return false;
+    if (prefix[0] != 'E' || prefix[1] != 'x' || prefix[2] != 'i' || prefix[3] != 'f' || prefix[4] != 0 || prefix[5] != 0)
+        return false;
+    return true;
+}
+
+/*
+ * Returns -1 on error
+ * Returns 0 if no Exif orientation was found
+ * Returns 1 orientation is horizontal (normal)
+ * Returns 2 mirror horizontal
+ * Returns 3 rotate 180
+ * Returns 4 mirror vertical
+ * Returns 5 mirror horizontal and rotate 270 CCW
+ * Returns 6 rotate 90 CW
+ * Returns 7 mirror horizontal and rotate 90 CW
+ * Returns 8 rotate 270 CW
+ */
+static int getExifOrientation(QByteArray &exifData)
+{
+    QDataStream stream(&exifData, QIODevice::ReadOnly);
+
+    if (!readExifHeader(stream))
+        return -1;
+
+    quint16 val;
+    quint32 offset;
+
+    // read byte order marker
+    stream >> val;
+    if (val == 0x4949) // 'II' == Intel
+        stream.setByteOrder(QDataStream::LittleEndian);
+    else if (val == 0x4d4d) // 'MM' == Motorola
+        stream.setByteOrder(QDataStream::BigEndian);
+    else
+        return -1; // unknown byte order
+
+    // read size
+    stream >> val;
+    if (val != 0x2a)
+        return -1;
+
+    stream >> offset;
+    // we have already used 8 bytes of TIFF header
+    offset -= 8;
+
+    // read IFD
+    while (!stream.atEnd()) {
+        quint16 numEntries;
+
+        // skip offset bytes to get the next IFD
+        if (stream.skipRawData(offset) != (qint32)offset)
+            return -1;
+
+        stream >> numEntries;
+
+        for (;numEntries > 0; --numEntries) {
+            quint16 tag;
+            quint16 type;
+            quint32 components;
+            quint32 value;
+
+            stream >> tag >> type >> components >> value;
+
+            if (tag == 0x0112) { // Tag Exif.Image.Orientation
+                if (components !=1)
+                    return -1;
+                if (type != 3) // we are expecting it to be an unsigned short
+                    return -1;
+                if (value < 1 || value > 8) // check for valid range
+                    return -1;
+
+                // It is possible to include the orientation multiple times.
+                // Right now the first value is returned.
+                return value;
+            }
+        }
+
+        // read offset to next IFD
+        stream >> offset;
+        if (offset == 0) // this is the last IFD
+            break;
+    }
+
+    // No Exif orientation was found
+    return 0;
+}
 /*!
     \internal
 */
@@ -779,6 +872,7 @@ bool QJpegHandlerPrivate::readJpegHeader(QIODevice *device)
 
         if (!setjmp(err.setjmp_buffer)) {
             jpeg_save_markers(&info, JPEG_COM, 0xFFFF);
+            jpeg_save_markers(&info, JPEG_APP0+1, 0xFFFF); // Exif uses APP1 marker
 
             (void) jpeg_read_header(&info, TRUE);
 
@@ -790,6 +884,8 @@ bool QJpegHandlerPrivate::readJpegHeader(QIODevice *device)
             format = QImage::Format_Invalid;
             read_jpeg_format(format, &info);
 
+            QByteArray exifData;
+
             for (jpeg_saved_marker_ptr marker = info.marker_list; marker != NULL; marker = marker->next) {
                 if (marker->marker == JPEG_COM) {
                     QString key, value;
@@ -807,9 +903,18 @@ bool QJpegHandlerPrivate::readJpegHeader(QIODevice *device)
                     description += key + QLatin1String(": ") + value.simplified();
                     readTexts.append(key);
                     readTexts.append(value);
+                } else if (marker->marker == JPEG_APP0+1) {
+                    exifData.append((const char*)marker->data, marker->data_length);
                 }
             }
 
+            if (exifData.size()) {
+                // Exif data present
+                int orientation = getExifOrientation(exifData);
+                if (orientation > 0)
+                    exifOrientation = orientation;
+            }
+
             state = ReadHeader;
             return true;
         }
@@ -823,6 +928,48 @@ bool QJpegHandlerPrivate::readJpegHeader(QIODevice *device)
     return true;
 }
 
+void QJpegHandlerPrivate::applyExifOrientation(QImage *image)
+{
+    // This is not an optimized implementation, but easiest to maintain
+    QTransform transform;
+
+    switch (exifOrientation) {
+        case 1: // normal
+            break;
+        case 2: // mirror horizontal
+            *image = image->mirrored(true, false);
+            break;
+        case 3: // rotate 180
+            transform.rotate(180);
+            *image = image->transformed(transform);
+            break;
+        case 4: // mirror vertical
+            *image = image->mirrored(false, true);
+            break;
+        case 5: // mirror horizontal and rotate 270 CCW
+            *image = image->mirrored(true, false);
+            transform.rotate(270);
+            *image = image->transformed(transform);
+            break;
+        case 6: // rotate 90 CW
+            transform.rotate(90);
+            *image = image->transformed(transform);
+            break;
+        case 7: // mirror horizontal and rotate 90 CW
+            *image = image->mirrored(true, false);
+            transform.rotate(90);
+            *image = image->transformed(transform);
+            break;
+        case 8: // rotate 270 CW
+            transform.rotate(-90);
+            *image = image->transformed(transform);
+            break;
+        default:
+            qWarning("This should never happen");
+    }
+    exifOrientation = 1;
+}
+
 bool QJpegHandlerPrivate::read(QImage *image)
 {
     if(state == Ready)
@@ -834,6 +981,7 @@ bool QJpegHandlerPrivate::read(QImage *image)
         if (success) {
             for (int i = 0; i < readTexts.size()-1; i+=2)
                 image->setText(readTexts.at(i), readTexts.at(i+1));
+            applyExifOrientation(image);
 
             state = Ready;
             return true;

tests/auto/gui/image/qimage/tst_qimage.cpp

@@ -173,6 +173,8 @@ private slots:
     void invertPixelsRGB_data();
     void invertPixelsRGB();
 
+    void exifOrientation();
+
     void cleanupFunctions();
 
 private:
@@ -2624,6 +2626,22 @@ void tst_QImage::invertPixelsRGB()
     QCOMPARE(qBlue(pixel) >> 4, (255 - 96) >> 4);
 }
 
+void tst_QImage::exifOrientation()
+{
+    for (unsigned int i = 1; i <= 8; ++i) {
+        QImage img;
+        QRgb px;
+
+        QVERIFY(img.load(m_prefix + QString::fromLatin1("jpeg_exif_orientation_value_%1.jpg").arg(i)));
+
+        px = img.pixel(0, 0);
+        QVERIFY(qRed(px) > 250 && qGreen(px) < 5 && qBlue(px) < 5);
+
+        px = img.pixel(img.width() - 1, 0);
+        QVERIFY(qRed(px) < 5 && qGreen(px) < 5 && qBlue(px) > 250);
+    }
+}
+
 static void cleanupFunction(void* info)
 {
     bool *called = static_cast<bool*>(info);