I agree we should have a separate row-based downscaling phase. JPEGImageDecoder.cpp already supports downscaling with a given width and height, but it's using point sampling which has poor quality. It would be nice to have a callback based downscaling API that we can implement better algorithms.
Alpha 2012/8/13 Alpha (Hin-Chung) Lam <hc...@google.com> > I agree we should have a separate row-based downscaling phase. > > JPEGImageDecoder.cpp already supports downscaling with a given width and > height, but it's using point sampling which has poor quality. It would be > nice to have a callback based downscaling API that we can implement better > algorithms. > > Alpha > > > 2012/8/13 Ilyes Gouta <ilyes.go...@gmail.com> > >> Hi, >> >> On Mon, Aug 13, 2012 at 3:46 PM, Anton Obzhirov <a.obzhi...@samsung.com> >> wrote: >> > Libjpeg has some internal support for downscaling already (2x, 4x). Not >> sure >> > about >> > >> > Libpng and other libraries. In general probably it can be implemented >> by >> > downscaling decoded row of the pixels on the fly using callback API >> > provided. >> >> If such a callback API for row-based resizing comes to fruition, then >> let's (also) not rule out whole-picture h/w accelerated resizing - >> such as by making that new API a mandatory stage in the decoding >> process. >> >> -Ilyes >> >> > >> > From: tomhud...@google.com [mailto:tomhud...@google.com] On Behalf Of >> Tom >> > Hudson >> > Sent: 13 August 2012 15:00 >> > To: webkit-dev@lists.webkit.org; Anton Obzhirov >> > Subject: Fwd: [webkit-dev] image downscaling during decoding >> > >> > >> > >> > On Mon, Aug 13, 2012 at 9:39 AM, Anton Obzhirov <a.obzhi...@samsung.com >> > >> > wrote: >> > >> > >> > >> > We are looking for ways to improve page loading speed and reduce memory >> > usage for WebKit in general and for GTK port of WebKit in particular. >> > >> > One of the ideas is to implement downscaling of the images during >> decoding >> > for image elements with rectangle less then original image size. >> > >> > At the moment such images are full decoded to a full size buffer and get >> > downscaled during rendering. >> > >> > It can be quite beneficial in term of memory usage and should speed up >> > rendering of the pages like image galleries for example. >> > >> > So what are your thoughts about it? >> > >> > >> > >> > Interesting idea! I know Chrome sees memory pressure from the >> downsampling >> > two-step on some pages, so I'd think this is could be useful for us, >> too. >> > >> > >> > >> > Isn't it going to require fairly large and intrusive changes to several >> > different third-party libraries, though? >> > >> > Also, different ports use different image downscaling algorithms; I can >> > think of ways to try to enable incremental downscaling callbacks so you >> > don't have to implement N downscales in each of M decoders, but none >> that >> > are both general and performant. >> > >> > >> > >> > I'd love to see a proposal on this. >> > >> > >> > >> > Tom >> > >> > (from the right account this time) >> > >> > >> > _______________________________________________ >> > webkit-dev mailing list >> > webkit-dev@lists.webkit.org >> > http://lists.webkit.org/mailman/listinfo/webkit-dev >> > >> _______________________________________________ >> webkit-dev mailing list >> webkit-dev@lists.webkit.org >> http://lists.webkit.org/mailman/listinfo/webkit-dev >> > >
_______________________________________________ webkit-dev mailing list webkit-dev@lists.webkit.org http://lists.webkit.org/mailman/listinfo/webkit-dev
