[webkit-qt] performance opportunities in graphics processing
benjamin.poulain at nokia.com
Tue Oct 26 09:41:09 PDT 2010
On 10/26/2010 06:11 PM, ext chunrong lai wrote:
> In my understanding we do not need such transforms if we draw/scale
> a pixmap to a smaller size. Isn't it?
I am not sure why you think that.
> + float tsw = src.width();
> + float tsh = src.height();
> + float tw = dst.width();
> + float th = dst.height();
> + if( tw <= tsw && th <= tsh )
> painter->setRenderHint(QPainter::SmoothPixmapTransform, false);
> painter->drawPixmap(dst, *image, src);
This will give aliasing when you rotate + scale.
> for some QImage::Format_RGB32 pages which are stored using a 32-bit RGB
> format (0xffRRGGBB) but regarded as without alpha channel according to
> I wonder if QImage::Format_RGB32 can be just regarded as a special case
> (always 0xFF alpha) of Format_ARGB32? What is the side-effect to keep
> the CompositionMode_SourceOver mode here beside the observed performance
You definitively don't want to consider RGB32 as a special case of
ARGB32. Composition source over of an opaque pixel is a memcopy, a
non-opaque pixel require alpha blending.
As Ariya mentioned, I would extend the definition of fast_images.
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