Introduce QImage::reinterpretAsFormat

QImage::reinterpretAsFormat can be used to change the format of an image
without converting the data, to correct wrong formats or narrow the
format to an opaque one if found to be opaque.

[ChangeLog][QtGui][QImage] A new method reinterpretAsFormat is has been
added to change the format of a QImage without converting the data.

Change-Id: I5e15bc5a1c474a35d3921b06299008ab2effd945
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

1 files changed, 63 insertions, 0 deletions

diff --git a/tests/auto/gui/image/qimage/tst_qimage.cpp b/tests/auto/gui/image/qimage/tst_qimage.cpp
index 65ee4a2188..21481e374d 100644
--- a/tests/auto/gui/image/qimage/tst_qimage.cpp
+++ b/tests/auto/gui/image/qimage/tst_qimage.cpp
@@ -206,6 +206,11 @@ private slots:
     void ditherGradient_data();
     void ditherGradient();
 
+    void reinterpretAsFormat_data();
+    void reinterpretAsFormat();
+
+    void reinterpretAsFormat2();
+
 #ifdef Q_OS_DARWIN
     void toCGImage_data();
     void toCGImage();
@@ -3303,6 +3308,64 @@ void tst_QImage::ditherGradient()
     QVERIFY(observedGradientSteps >= minimumExpectedGradient);
 }
 
+void tst_QImage::reinterpretAsFormat_data()
+{
+    QTest::addColumn<QImage::Format>("in_format");
+    QTest::addColumn<QImage::Format>("out_format");
+    QTest::addColumn<QColor>("in_color");
+    QTest::addColumn<QColor>("out_color");
+
+#if Q_BYTE_ORDER == Q_LITTLE_ENDIAN
+    QTest::newRow("rgb32 -> rgbx8888") << QImage::Format_RGB32 << QImage::Format_RGBX8888 << QColor(Qt::red) << QColor(Qt::blue);
+    QTest::newRow("rgba8888 -> argb32") << QImage::Format_RGBA8888 << QImage::Format_ARGB32 << QColor(Qt::red) << QColor(Qt::blue);
+    QTest::newRow("argb32pm -> rgba8888pm") << QImage::Format_RGBA8888_Premultiplied << QImage::Format_ARGB32_Premultiplied << QColor(Qt::green) << QColor(Qt::green);
+#endif
+    QTest::newRow("rgb32 -> argb32") << QImage::Format_RGB32 << QImage::Format_ARGB32 << QColor(Qt::cyan) << QColor(Qt::cyan);
+    QTest::newRow("argb32pm -> rgb32") << QImage::Format_ARGB32_Premultiplied << QImage::Format_RGB32 << QColor(Qt::transparent) << QColor(Qt::black);
+    QTest::newRow("argb32 -> rgb32") << QImage::Format_ARGB32 << QImage::Format_RGB32 << QColor(255, 0, 0, 127) << QColor(255, 0, 0);
+    QTest::newRow("argb32pm -> rgb32") << QImage::Format_ARGB32_Premultiplied << QImage::Format_RGB32 << QColor(255, 0, 0, 127) << QColor(127, 0, 0);
+}
+
+void tst_QImage::reinterpretAsFormat()
+{
+    QFETCH(QImage::Format, in_format);
+    QFETCH(QImage::Format, out_format);
+    QFETCH(QColor, in_color);
+    QFETCH(QColor, out_color);
+
+    QImage image(1, 1, in_format);
+    image.setPixelColor(0, 0, in_color);
+    QVERIFY(image.reinterpretAsFormat(out_format));
+    QCOMPARE(image.pixelColor(0, 0), out_color);
+}
+
+void tst_QImage::reinterpretAsFormat2()
+{
+    const uint imageData[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
+
+    {
+        QImage image(reinterpret_cast<const uchar*>(imageData), 4, 2, QImage::Format_RGB32);
+        QCOMPARE(image.pixelColor(0, 0), QColor(Qt::black));
+        QVERIFY(image.isDetached());
+        QVERIFY(image.reinterpretAsFormat(QImage::Format_ARGB32_Premultiplied));
+        QCOMPARE(image.constBits(), reinterpret_cast<const uchar*>(imageData));
+        QCOMPARE(image.pixelColor(0, 0), QColor(Qt::transparent));
+
+        QVERIFY(!image.reinterpretAsFormat(QImage::Format_Grayscale8));
+    }
+    {
+        QImage image(reinterpret_cast<const uchar*>(imageData), 8, 4, QImage::Format_Indexed8);
+        image.setColor(0, qRgb(255, 255, 255));
+        QCOMPARE(image.pixelColor(0, 0), QColor(Qt::white));
+        QVERIFY(image.reinterpretAsFormat(QImage::Format_Grayscale8));
+        QCOMPARE(image.pixelColor(0, 0), QColor(Qt::black));
+        QVERIFY(image.reinterpretAsFormat(QImage::Format_Alpha8));
+        QCOMPARE(image.pixelColor(0, 0), QColor(Qt::transparent));
+
+        QVERIFY(!image.reinterpretAsFormat(QImage::Format_RGB16));
+    }
+}
+
 #ifdef Q_OS_DARWIN
 
 void tst_QImage::toCGImage_data()