On Fri, 19 May 2006 11:35:44 +0100 Stephen GALLIMORE <[EMAIL PROTECTED]> babbled:
> Denis, > > I am currently trying to support a customer who wants to use > the EVAS (enlightenment) library on top of DirectFB, on an > STMicroelectronics set top box SoC. One of the things that > EVAS does when blitting images with alpha is switch on > _both_ DSBLIT_BLEND_COLORALPHA and > DSBLIT_BLEND_ALPHACHANNEL. > > I have been asked to support this blend flag combination > in hardware, in order to get the performance the customer > wants with the EVAS library, and am having difficulty > producing the same results as the software rasterizer. I have > to admit that up to now, based on the one line descriptions > of these flags in the API doc, I had assumed they were > mutually exclusive. But they are clearly not. > > Could you please clarify for me exactly what the behaviour > of DSBLIT_BLEND_COLORALPHA is, both on its own > and in combination with DSBLIT_BLEND_ALPHACHANNEL. > I am particularly interested in the case where the source > has an alpha channel and the RGB components are already > pre-multiplied by the source alpha. really? evas doesn't use premul-alpha in its software or gl engines, and the xrender engine converts to premul to keep xrender happy. (nb - this is on the todo list to change to premul internally). > As an aside, is there a diagram anywhere that shows the > whole pipeline and the operations done at each stage. > That would be a very useful reference for driver writers. > > Best Regards, > -stephen > > > _______________________________________________ > directfb-dev mailing list > [email protected] > http://mail.directfb.org/cgi-bin/mailman/listinfo/directfb-dev > -- ------------- Codito, ergo sum - "I code, therefore I am" -------------- The Rasterman (Carsten Haitzler) [EMAIL PROTECTED] 裸好多 Tokyo, Japan (東京 日本) _______________________________________________ directfb-dev mailing list [email protected] http://mail.directfb.org/cgi-bin/mailman/listinfo/directfb-dev
