[webkit-qt] performance opportunities in graphics processing

[chunrong lai]

 As filed in  https://bugs.webkit.org/show_bug.cgi?id=50807,
 attached updated patch tries to disable the SmoothPixmapTransforms in
drawing images which are scaled to smaller size but without rotation. Does
it make sense? I can see it improves the performance of the attached test
page by 6X~7X. :-)

diff -BburN qt.old/ImageQt.cpp qt/ImageQt.cpp
--- qt.old/ImageQt.cpp 2010-12-08 15:26:15.237726493 +0800
+++ qt/ImageQt.cpp 2010-12-09 18:22:20.817755997 +0800
@@ -189,6 +189,13 @@

     // Test using example site at
     // http://www.meyerweb.com/eric/css/edge/complexspiral/demo.html
+    float tsw = src.width();
+    float tsh = src.height();
+    float tw = dst.width();
+    float th = dst.height();
+    if( tw <= tsw && th <= tsh &&
ctxt->platformContext()->combinedTransform().type() <= QTransform::TxScale){
+        painter->setRenderHint(QPainter::SmoothPixmapTransform, false);
+    }
     painter->drawPixmap(dst, *image, src);

On 10/26/2010 06:11 PM, Benjamin Poulain wrote:
>  Hi
>  I am not sure why you think that.
>*  *This will give aliasing when you rotate + scale.
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