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. 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
