Fix setScaledClipRect autotest for reading SVG format

Since setScaledClipRect will actually render only the necessary parts,
there may be insignificant differences in rounding/anitaliasing
compared to rendering the whole image first and then clipping.

Hence this autotest case would always fail. But that would not happen
in CI, since it tests qtbase without the qtsvg module, and then the
SVG tests are skipped. (For some reason, one ran into this in wayland
testing and made an exception for that, but obviously this failure has
nothing to do with wayland).

Work around the issue by converting the rendered images to 4 bpc
format, so the differences in the least significant bits get truncated
away.

Fixes: QTBUG-100917
Task-number: QTBUG-81044
Pick-to: 6.4
Change-Id: I1c14e98af22d0ae22a751960b69e692c7a38399b
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

1 files changed, 5 insertions, 2 deletions

diff --git a/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp b/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
index b01eb83089..42a2efe5a8 100644
--- a/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
+++ b/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
@@ -487,8 +487,11 @@ void tst_QImageReader::setScaledClipRect()
     QImageReader originalReader(prefix + fileName);
     originalReader.setScaledSize(QSize(300, 300));
     QImage originalImage = originalReader.read();
-    if (QGuiApplication::platformName().startsWith(QLatin1String("wayland"), Qt::CaseInsensitive) && format.contains("svg"))
-        QEXPECT_FAIL("", "This fails on Wayland, see QTBUG-100917.", Abort);
+    if (format.contains("svg")) {
+        // rendering of subrect may yield slight rounding differences, truncate them away
+        image.convertTo(QImage::Format_RGB444);
+        originalImage.convertTo(QImage::Format_RGB444);
+    }
     QCOMPARE(originalImage.copy(newRect), image);
 }