Ensured correct rounding of scaled image drawing at non-integer coords.

Images coordinates should simply be rounded and are not to be subject
to the aliased coordinate delta. The patch also adds a tiny delta in
QSpanData::setupMatrix() to ensure coordinates for fetching from source
images are rounded the opposite direction of the target rectangle.
This removes a lot of artifacts when trying to do border-image based
drawing on non-integer coordinates. A new qps test for border-image
drawing is included.

Task-number: 251561
Reviewed-by: Trond

1 files changed, 12 insertions, 2 deletions

diff --git a/src/gui/painting/qpaintengine_raster.cpp b/src/gui/painting/qpaintengine_raster.cpp
index e249b3e..788b722 100644
--- a/src/gui/painting/qpaintengine_raster.cpp
+++ b/src/gui/painting/qpaintengine_raster.cpp
@@ -2664,7 +2664,13 @@ void QRasterPaintEngine::drawImage(const QRectF &r, const QImage &img, const QRe
 
         QRectF rr = r;
         rr.translate(s->matrix.dx(), s->matrix.dy());
-        fillRect_normalized(toRect_normalized(rr), &d->image_filler, d);
+
+        const int x1 = qRound(rr.x());
+        const int y1 = qRound(rr.y());
+        const int x2 = qRound(rr.right());
+        const int y2 = qRound(rr.bottom());
+
+        fillRect_normalized(QRect(x1, y1, x2-x1, y2-y1), &d->image_filler, d);
     }
 }
 
@@ -5147,7 +5153,11 @@ void QSpanData::adjustSpanMethods()
 
 void QSpanData::setupMatrix(const QTransform &matrix, int bilin)
 {
-    QTransform inv = matrix.inverted();
+    QTransform delta;
+    // make sure we round off correctly in qdrawhelper.cpp
+    delta.translate(1.0 / 65536, 1.0 / 65536);
+
+    QTransform inv = (delta * matrix).inverted();
     m11 = inv.m11();
     m12 = inv.m12();
     m13 = inv.m13();