Set the resolution when saving a tiff file

The resolution was not saved when the image was saved
as tiff. This fix add the resolution, and try to guess if the user have
set it in dpi or dot per centimeter

Task-number: 245242
Reviewed-by: Samuel

2 files changed, 56 insertions, 2 deletions

diff --git a/src/plugins/imageformats/tiff/qtiffhandler.cpp b/src/plugins/imageformats/tiff/qtiffhandler.cpp
index 518e6d1..77dfeb3 100644
--- a/src/plugins/imageformats/tiff/qtiffhandler.cpp
+++ b/src/plugins/imageformats/tiff/qtiffhandler.cpp
@@ -168,7 +168,7 @@ bool QTiffHandler::read(QImage *image)
                         break;
                     default:
                         // do nothing as defaults have already
-						// been set within the QImage class
+                        // been set within the QImage class
                         break;
                 }
                 for (uint32 y=0; y<height; ++y)
@@ -218,6 +218,24 @@ bool QTiffHandler::write(const QImage &image)
             return false;
         }
 
+        // set the resolution
+        bool  resolutionSet = false;
+        const int dotPerMeterX = image.dotsPerMeterX();
+        const int dotPerMeterY = image.dotsPerMeterY();
+        if ((dotPerMeterX % 100) == 0
+                && (dotPerMeterY % 100) == 0) {
+            resolutionSet = TIFFSetField(tiff, TIFFTAG_RESOLUTIONUNIT, RESUNIT_CENTIMETER)
+                && TIFFSetField(tiff, TIFFTAG_XRESOLUTION, dotPerMeterX/100.0)
+                && TIFFSetField(tiff, TIFFTAG_YRESOLUTION, dotPerMeterY/100.0);
+        } else {
+            resolutionSet = TIFFSetField(tiff, TIFFTAG_RESOLUTIONUNIT, RESUNIT_INCH)
+                && TIFFSetField(tiff, TIFFTAG_XRESOLUTION, static_cast<float>(image.logicalDpiX()))
+                && TIFFSetField(tiff, TIFFTAG_YRESOLUTION, static_cast<float>(image.logicalDpiY()));
+        }
+        if (!resolutionSet) {
+            TIFFClose(tiff);
+            return false;
+        }
         // try to do the ARGB32 conversion in chunks no greater than 16 MB
         int chunks = (width * height * 4 / (1024 * 1024 * 16)) + 1;
         int chunkHeight = qMax(height / chunks, 1);
diff --git a/tests/auto/qimagewriter/tst_qimagewriter.cpp b/tests/auto/qimagewriter/tst_qimagewriter.cpp
index 878d398..70d9e70 100644
--- a/tests/auto/qimagewriter/tst_qimagewriter.cpp
+++ b/tests/auto/qimagewriter/tst_qimagewriter.cpp
@@ -97,6 +97,9 @@ private slots:
     void saveWithNoFormat_data();
     void saveWithNoFormat();
 
+    void resolution_data();
+    void resolution();
+
     void saveToTemporaryFile();
 };
 
@@ -162,7 +165,7 @@ tst_QImageWriter::tst_QImageWriter()
 
 tst_QImageWriter::~tst_QImageWriter()
 {
-    QDir dir("images");
+    QDir dir(prefix + QLatin1String("images"));
     QStringList filesToDelete = dir.entryList(QStringList() << "gen-*" , QDir::NoDotAndDotDot | QDir::Files);
     foreach( QString file, filesToDelete) {
         QFile::remove(dir.absoluteFilePath(file));
@@ -530,6 +533,39 @@ void tst_QImageWriter::saveWithNoFormat()
     QVERIFY2(!outImage.isNull(), qPrintable(reader.errorString()));
 }
 
+void tst_QImageWriter::resolution_data()
+{
+    QTest::addColumn<QString>("filename");
+    QTest::addColumn<int>("expectedDotsPerMeterX");
+    QTest::addColumn<int>("expectedDotsPerMeterY");
+#if defined QTEST_HAVE_TIFF
+    QTest::newRow("TIFF: 100 dpi") << ("image_100dpi.tif") << qRound(100 * (100 / 2.54)) << qRound(100 * (100 / 2.54));
+    QTest::newRow("TIFF: 50 dpi") << ("image_50dpi.tif") << qRound(50 * (100 / 2.54)) << qRound(50 * (100 / 2.54));
+    QTest::newRow("TIFF: 300 dot per meter") << ("image_300dpm.tif") << 300 << 300;
+#endif
+}
+
+void tst_QImageWriter::resolution()
+{
+    QFETCH(QString, filename);
+    QFETCH(int, expectedDotsPerMeterX);
+    QFETCH(int, expectedDotsPerMeterY);
+
+    QImage image(prefix + QLatin1String("colorful.bmp"));
+    image.setDotsPerMeterX(expectedDotsPerMeterX);
+    image.setDotsPerMeterY(expectedDotsPerMeterY);
+    const QString generatedFilepath = prefix + "gen-" + filename;
+    {
+        QImageWriter writer(generatedFilepath);
+        QVERIFY(writer.write(image));
+    }
+    QImageReader reader(generatedFilepath);
+    const QImage generatedImage = reader.read();
+
+    QCOMPARE(expectedDotsPerMeterX, generatedImage.dotsPerMeterX());
+    QCOMPARE(expectedDotsPerMeterY, generatedImage.dotsPerMeterY());
+}
+
 void tst_QImageWriter::saveToTemporaryFile()
 {
     QImage image(prefix + "kollada.png");