QImage/Jpeg: decode/encode comment attributes as utf-8

Although not defined, the jpeg comment field 'content' is treated as
utf-8 nowadys. At least exiftool and exiv2 (tested via gwenview) are
expecting utf-8 here. So we should do the same.

Task-number: QTBUG-44709
Change-Id: If84dafac3e337c7993f09cd59792e721977c9adb
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

3 files changed, 32 insertions, 3 deletions

diff --git a/src/plugins/imageformats/jpeg/qjpeghandler.cpp b/src/plugins/imageformats/jpeg/qjpeghandler.cpp
index 1cdc28c077..e52a19703c 100644
--- a/src/plugins/imageformats/jpeg/qjpeghandler.cpp
+++ b/src/plugins/imageformats/jpeg/qjpeghandler.cpp
@@ -493,10 +493,10 @@ static inline void set_text(const QImage &image, j_compress_ptr cinfo, const QSt
 {
     const QMap<QString, QString> text = qt_getImageText(image, description);
     for (auto it = text.begin(), end = text.end(); it != end; ++it) {
-        QByteArray comment = it.key().toLatin1();
+        QByteArray comment = it.key().toUtf8();
         if (!comment.isEmpty())
             comment += ": ";
-        comment += it.value().toLatin1();
+        comment += it.value().toUtf8();
         if (comment.length() > 65530)
             comment.truncate(65530);
         jpeg_write_marker(cinfo, JPEG_COM, (const JOCTET *)comment.constData(), comment.size());
@@ -904,7 +904,7 @@ bool QJpegHandlerPrivate::readJpegHeader(QIODevice *device)
             for (jpeg_saved_marker_ptr marker = info.marker_list; marker != NULL; marker = marker->next) {
                 if (marker->marker == JPEG_COM) {
                     QString key, value;
-                    QString s = QString::fromLatin1((const char *)marker->data, marker->data_length);
+                    QString s = QString::fromUtf8((const char *)marker->data, marker->data_length);
                     int index = s.indexOf(QLatin1String(": "));
                     if (index == -1 || s.indexOf(QLatin1Char(' ')) < index) {
                         key = QLatin1String("Description");
diff --git a/tests/auto/gui/image/qimage/images/jpeg_exif_utf8_comment.jpg b/tests/auto/gui/image/qimage/images/jpeg_exif_utf8_comment.jpg
new file mode 100644
index 0000000000..42b305f5b8
--- /dev/null
+++ b/tests/auto/gui/image/qimage/images/jpeg_exif_utf8_comment.jpg
diff --git a/tests/auto/gui/image/qimage/tst_qimage.cpp b/tests/auto/gui/image/qimage/tst_qimage.cpp
index 7ad4a9e9bb..55a670eb6f 100644
--- a/tests/auto/gui/image/qimage/tst_qimage.cpp
+++ b/tests/auto/gui/image/qimage/tst_qimage.cpp
@@ -192,6 +192,7 @@ private slots:
     void exif_QTBUG45865();
     void exifInvalidData_data();
     void exifInvalidData();
+    void exifReadComments();
 
     void cleanupFunctions();
 
@@ -3066,6 +3067,34 @@ void tst_QImage::exifInvalidData()
     QVERIFY(!image.isNull());
 }
 
+void tst_QImage::exifReadComments()
+{
+    QImage image;
+    QVERIFY(image.load(m_prefix + "jpeg_exif_utf8_comment.jpg"));
+    QVERIFY(!image.isNull());
+    QCOMPARE(image.textKeys().size(), 1);
+    QCOMPARE(image.textKeys().first(), "Description");
+    // check if exif comment is read as utf-8
+    QCOMPARE(image.text("Description"), QString::fromUtf8("some unicode chars: ÖÄÜ€@"));
+
+    QByteArray ba;
+    {
+        QBuffer buf(&ba);
+        QVERIFY(buf.open(QIODevice::WriteOnly));
+        QVERIFY(image.save(&buf, "JPG"));
+    }
+    QVERIFY(!ba.isEmpty());
+    image = QImage();
+    QCOMPARE(image.textKeys().size(), 0);
+    {
+        QBuffer buf(&ba);
+        QVERIFY(buf.open(QIODevice::ReadOnly));
+        QVERIFY(image.load(&buf, "JPG"));
+    }
+    // compare written (and reread) description text
+    QCOMPARE(image.text("Description"), QString::fromUtf8("some unicode chars: ÖÄÜ€@"));
+}
+
 static void cleanupFunction(void* info)
 {
     bool *called = static_cast<bool*>(info);