HEIF: Resolve primary image index from image source

The primary image, in the case of multi-image sources, may not
necessarily be the first image.

Test images produced with patched version of enc-heif that
allowed overriding the primary image. The correct primary
image is green, while the other image is red.

Change-Id: Iba26b13fdb4898d7babc5fb173ad38b16f864e80
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit 1bf5692d3f)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/plugins/imageformats/shared/qiiofhelpers.cpp

@@ -116,8 +116,10 @@ bool QIIOFHelper::initRead()
 
     cgImageSource = CGImageSourceCreateWithDataProvider(cgDataProvider, nullptr);
 
-    if (cgImageSource)
-        cfImageDict = CGImageSourceCopyPropertiesAtIndex(cgImageSource, 0, nullptr);
+    if (cgImageSource) {
+        auto primaryIndex = CGImageSourceGetPrimaryImageIndex(cgImageSource);
+        cfImageDict = CGImageSourceCopyPropertiesAtIndex(cgImageSource, primaryIndex, nullptr);
+    }
 
     return (cgImageSource);
 }
@@ -127,7 +129,8 @@ bool QIIOFHelper::readImage(QImage *out)
     if (!out || !initRead())
         return false;
 
-    QCFType<CGImageRef> cgImage = CGImageSourceCreateImageAtIndex(cgImageSource, 0, nullptr);
+    auto primaryIndex = CGImageSourceGetPrimaryImageIndex(cgImageSource);
+    QCFType<CGImageRef> cgImage = CGImageSourceCreateImageAtIndex(cgImageSource, primaryIndex, nullptr);
     if (!cgImage)
         return false;
 

tests/auto/heif/CMakeLists.txt

@@ -16,6 +16,8 @@ qt_internal_add_test(tst_qheif
 set(heif_resource_files
     "../../shared/images/heif/col320x480.heic"
     "../../shared/images/heif/newlogoCCW.heic"
+    "../../shared/images/heif/primary-index-0.heic"
+    "../../shared/images/heif/primary-index-1.heic"
 )
 
 qt_internal_add_resource(tst_qheif "heif"

tests/auto/heif/tst_qheif.cpp

@@ -15,6 +15,9 @@ private slots:
     void readProperties_data();
     void readProperties();
     void writeImage();
+
+    void primaryIndex_data();
+    void primaryIndex();
 };
 
 void tst_qheif::initTestCase()
@@ -123,5 +126,22 @@ void tst_qheif::writeImage()
     }
 }
 
+void tst_qheif::primaryIndex_data()
+{
+    QTest::addColumn<int>("primaryIndex");
+
+    QTest::newRow("0 (first/default)") << 0;
+    QTest::newRow("1 (second)") << 1;
+}
+
+void tst_qheif::primaryIndex()
+{
+    QFETCH(int, primaryIndex);
+
+    QImage image(QString(":/heif/primary-index-%1.heic").arg(primaryIndex));
+    QVERIFY(!image.isNull());
+    QCOMPARE(image.pixelColor(50, 50), QColor(Qt::green));
+}
+
 QTEST_MAIN(tst_qheif)
 #include "tst_qheif.moc"