QImageReader: allow only one dimension to be used for scaledSize

If only one dimension (width or height) of the scaled size is set
by an user, let's try to calculate the second one, based on the
image original size and maintaining the aspect ratio.

[ChangeLog][QtGui][QImageReader] Allow only one dimension (width
or height) to be set for the scaled size. In this case, the other
will be calculated automatically based on the original image size
and maintaining the aspect ratio.

Task-number: QTBUG-115039
Change-Id: If1b13b1ead3cf788915c08bdb3ba8becd8bf8042
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

1 files changed, 57 insertions, 0 deletions

diff --git a/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp b/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
index a7011a2636..6d875ec0ab 100644
--- a/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
+++ b/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
@@ -62,6 +62,9 @@ private slots:
     void setScaledSize_data();
     void setScaledSize();
 
+    void setScaledSizeOneDimension_data();
+    void setScaledSizeOneDimension();
+
     void setClipRect_data();
     void setClipRect();
 
@@ -371,6 +374,60 @@ void tst_QImageReader::setScaledSize()
     QCOMPARE(image.size(), newSize);
 }
 
+void tst_QImageReader::setScaledSizeOneDimension_data()
+{
+    QTest::addColumn<QString>("fileName");
+    QTest::addColumn<QByteArray>("format");
+
+    QTest::newRow("PNG: kollada") << QString("kollada") << QByteArray("png");
+    QTest::newRow("JPEG: beavis") << QString("beavis") << QByteArray("jpeg");
+    QTest::newRow("GIF: earth") << QString("earth") << QByteArray("gif");
+    QTest::newRow("SVG: rect") << QString("rect") << QByteArray("svg");
+    QTest::newRow("BMP: colorful") << QString("colorful") << QByteArray("bmp");
+    QTest::newRow("XPM: marble") << QString("marble") << QByteArray("xpm");
+    QTest::newRow("PPM: teapot") << QString("teapot") << QByteArray("ppm");
+    QTest::newRow("XBM: gnus") << QString("gnus") << QByteArray("xbm");
+}
+
+void tst_QImageReader::setScaledSizeOneDimension()
+{
+    QFETCH(QString, fileName);
+    QFETCH(QByteArray, format);
+
+    SKIP_IF_UNSUPPORTED(format);
+
+    const QSize originalSize = QImageReader(prefix + fileName).size();
+    QVERIFY(!originalSize.isEmpty());
+
+    auto testScaledSize = [&] (const QSize &scaledSize) {
+        QSize expectedSize = scaledSize;
+        if (scaledSize.width() <= 0)
+            expectedSize.setWidth(qRound(originalSize.width() *
+                                         (qreal(scaledSize.height()) / originalSize.height())));
+        else if (scaledSize.height() <= 0)
+            expectedSize.setHeight(qRound(originalSize.height() *
+                                          (qreal(scaledSize.width()) / originalSize.width())));
+
+        QImageReader reader(prefix + fileName);
+        reader.setScaledSize(scaledSize);
+        QImage image = reader.read();
+        QVERIFY(!image.isNull());
+        QCOMPARE(image.size(), expectedSize);
+    };
+
+    // downscale
+    testScaledSize(QSize(originalSize.width() / 2, 0));
+    testScaledSize(QSize(originalSize.width() / 2, -1));
+    testScaledSize(QSize(0, originalSize.height() / 2));
+    testScaledSize(QSize(-1, originalSize.height() / 2));
+
+    // upscale
+    testScaledSize(QSize(originalSize.width() * 2, 0));
+    testScaledSize(QSize(originalSize.width() * 2, -1));
+    testScaledSize(QSize(0, originalSize.height() * 2));
+    testScaledSize(QSize(-1, originalSize.height() * 2));
+}
+
 void tst_QImageReader::task255627_setNullScaledSize_data()
 {
     setScaledSize_data();