Forward physical parameters for derived QImages

More specifically, for masks and rotated images.
Add tests for it, also add tests that image metadata is
forwarded for converted and copied images.

Fixes: QTBUG-49259
Change-Id: I05d4a468b17f53a2625500b871c01b2c53b981a1
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

2 files changed, 62 insertions, 9 deletions

diff --git a/src/gui/image/qimage.cpp b/src/gui/image/qimage.cpp
index 3e18ca6528..ed6f23ee56 100644
--- a/src/gui/image/qimage.cpp
+++ b/src/gui/image/qimage.cpp
@@ -1089,15 +1089,31 @@ void QImage::detach()
 }
 
 
-static void copyMetadata(QImageData *dst, const QImageData *src)
+static void copyPhysicalMetadata(QImageData *dst, const QImageData *src)
 {
-    // Doesn't copy colortable and alpha_clut, or offset.
     dst->dpmx = src->dpmx;
     dst->dpmy = src->dpmy;
     dst->devicePixelRatio = src->devicePixelRatio;
+}
+
+static void copyMetadata(QImageData *dst, const QImageData *src)
+{
+    // Doesn't copy colortable and alpha_clut, or offset.
+    copyPhysicalMetadata(dst, src);
     dst->text = src->text;
 }
 
+static void copyMetadata(QImage *dst, const QImage &src)
+{
+    dst->setDotsPerMeterX(src.dotsPerMeterX());
+    dst->setDotsPerMeterY(src.dotsPerMeterY());
+    dst->setDevicePixelRatio(src.devicePixelRatio());
+    const auto textKeys = src.textKeys();
+    for (const auto &key: textKeys)
+        dst->setText(key, src.text(key));
+
+}
+
 /*!
     \fn QImage QImage::copy(int x, int y, int width, int height) const
     \overload
@@ -2924,8 +2940,10 @@ QImage QImage::createAlphaMask(Qt::ImageConversionFlags flags) const
     }
 
     QImage mask(d->width, d->height, Format_MonoLSB);
-    if (!mask.isNull())
+    if (!mask.isNull()) {
         dither_to_Mono(mask.d, d, flags, true);
+        copyPhysicalMetadata(mask.d, d);
+    }
     return mask;
 }
 
@@ -3043,6 +3061,7 @@ QImage QImage::createHeuristicMask(bool clipTight) const
 
 #undef PIX
 
+    copyPhysicalMetadata(m.d, d);
     return m;
 }
 #endif //QT_NO_IMAGE_HEURISTIC_MASK
@@ -3086,6 +3105,8 @@ QImage QImage::createMaskFromColor(QRgb color, Qt::MaskMode mode) const
     }
     if  (mode == Qt::MaskOutColor)
         maskImage.invertPixels();
+
+    copyPhysicalMetadata(maskImage.d, d);
     return maskImage;
 }
 
@@ -4655,8 +4676,7 @@ QImage QImage::smoothScaled(int w, int h) const {
 static QImage rotated90(const QImage &image)
 {
     QImage out(image.height(), image.width(), image.format());
-    out.setDotsPerMeterX(image.dotsPerMeterY());
-    out.setDotsPerMeterY(image.dotsPerMeterX());
+    copyMetadata(&out, image);
     if (image.colorCount() > 0)
         out.setColorTable(image.colorTable());
     int w = image.width();
@@ -4684,8 +4704,7 @@ static QImage rotated180(const QImage &image)
         return image.mirrored(true, true);
 
     QImage out(image.width(), image.height(), image.format());
-    out.setDotsPerMeterX(image.dotsPerMeterY());
-    out.setDotsPerMeterY(image.dotsPerMeterX());
+    copyMetadata(&out, image);
     if (image.colorCount() > 0)
         out.setColorTable(image.colorTable());
     int w = image.width();
@@ -4697,8 +4716,7 @@ static QImage rotated180(const QImage &image)
 static QImage rotated270(const QImage &image)
 {
     QImage out(image.height(), image.width(), image.format());
-    out.setDotsPerMeterX(image.dotsPerMeterY());
-    out.setDotsPerMeterY(image.dotsPerMeterX());
+    copyMetadata(&out, image);
     if (image.colorCount() > 0)
         out.setColorTable(image.colorTable());
     int w = image.width();
diff --git a/tests/auto/gui/image/qimage/tst_qimage.cpp b/tests/auto/gui/image/qimage/tst_qimage.cpp
index 6bc27a6e16..bb81b9f61f 100644
--- a/tests/auto/gui/image/qimage/tst_qimage.cpp
+++ b/tests/auto/gui/image/qimage/tst_qimage.cpp
@@ -3260,11 +3260,46 @@ void tst_QImage::metadataPassthrough()
     QCOMPARE(mirrored.dotsPerMeterY(), a.dotsPerMeterY());
     QCOMPARE(mirrored.devicePixelRatio(), a.devicePixelRatio());
 
+    QTransform t;
+    t.rotate(90);
+    QImage rotated = a.transformed(t);
+    QCOMPARE(rotated.text(QStringLiteral("Test")), a.text(QStringLiteral("Test")));
+    QCOMPARE(rotated.dotsPerMeterX(), a.dotsPerMeterX());
+    QCOMPARE(rotated.dotsPerMeterY(), a.dotsPerMeterY());
+    QCOMPARE(rotated.devicePixelRatio(), a.devicePixelRatio());
+
     QImage swapped = a.rgbSwapped();
     QCOMPARE(swapped.text(QStringLiteral("Test")), a.text(QStringLiteral("Test")));
     QCOMPARE(swapped.dotsPerMeterX(), a.dotsPerMeterX());
     QCOMPARE(swapped.dotsPerMeterY(), a.dotsPerMeterY());
     QCOMPARE(swapped.devicePixelRatio(), a.devicePixelRatio());
+
+    QImage converted = a.convertToFormat(QImage::Format_RGB32);
+    QCOMPARE(converted.text(QStringLiteral("Test")), a.text(QStringLiteral("Test")));
+    QCOMPARE(converted.dotsPerMeterX(), a.dotsPerMeterX());
+    QCOMPARE(converted.dotsPerMeterY(), a.dotsPerMeterY());
+    QCOMPARE(converted.devicePixelRatio(), a.devicePixelRatio());
+
+    QImage copied = a.copy(0, 0, a.width() / 2, a.height() / 2);
+    QCOMPARE(copied.text(QStringLiteral("Test")), a.text(QStringLiteral("Test")));
+    QCOMPARE(copied.dotsPerMeterX(), a.dotsPerMeterX());
+    QCOMPARE(copied.dotsPerMeterY(), a.dotsPerMeterY());
+    QCOMPARE(copied.devicePixelRatio(), a.devicePixelRatio());
+
+    QImage alphaMask = a.createAlphaMask();
+    QCOMPARE(alphaMask.dotsPerMeterX(), a.dotsPerMeterX());
+    QCOMPARE(alphaMask.dotsPerMeterY(), a.dotsPerMeterY());
+    QCOMPARE(alphaMask.devicePixelRatio(), a.devicePixelRatio());
+
+    QImage heuristicMask = a.createHeuristicMask();
+    QCOMPARE(heuristicMask.dotsPerMeterX(), a.dotsPerMeterX());
+    QCOMPARE(heuristicMask.dotsPerMeterY(), a.dotsPerMeterY());
+    QCOMPARE(heuristicMask.devicePixelRatio(), a.devicePixelRatio());
+
+    QImage maskFromColor = a.createMaskFromColor(qRgb(0, 0, 0));
+    QCOMPARE(maskFromColor.dotsPerMeterX(), a.dotsPerMeterX());
+    QCOMPARE(maskFromColor.dotsPerMeterY(), a.dotsPerMeterY());
+    QCOMPARE(maskFromColor.devicePixelRatio(), a.devicePixelRatio());
 }
 
 void tst_QImage::pixelColor()