Jack, It sounds like you are running into the normal issue of classic blending. Classic blending assumes that there is nothing behind the destination but infinite blackness. The solution is to use pre-multiplied alpha surfaces and the appropriate Porter-Duff rule. Might I recommend DSPD_SRC_OVER. It will take some work to ensure that everything is pre-multiplied alpha. The image provider, if I remember correctly, will pre-multiply the colors if the surface cap is set to DSCAPS_PREMULTIPLIED. Also, the fonts I believe are pre-multiplied.
Quick Porter-Duff primer: Normal blending of semi-transparent colors results in "alpha holes" punched through opaque destination colors. (Suddenly I can see through the opaque wall! Or in your case, I see the video in the plane behind this one.) For Porter-Duff to work, all colors need to be pre-multiplied and the appropriate src/dst blend functions set. DirectFB provides a shortcut called SetPorterDuff that sets both at the same time. If you don't have pre-multiplied colors (and your graphics driver supports it), set DSBLIT_SRC_PREMULTIPLY to have the blender pre-multiply your source colors. Set DSBLIT_DST_PREMULTIPLY to pre-multiply your dest colors. And remember that the result of a Porter-Duff blend is also pre-multiplied, set DSBLIT_DEMULTIPLY if your destination isn't pre-multiplied. That should do it! Good luck! Bryce Poole Intel Corporation -----Original Message----- From: directfb-dev-boun...@directfb.org [mailto:directfb-dev-boun...@directfb.org] On Behalf Of MrPeach Sent: Thursday, April 02, 2009 1:34 PM To: directfb-dev@directfb.org Subject: [directfb-dev] df_andi and surface alpha Hi, Now that I have my DFB driver fully functional, our client is seeing things they don't like and are asking for us to resolve them. :/ When running df_andi, the status text is displayed in a rectangle in the upper left of the screen, and that rectangle is filled with a color which includes an alpha factor. That alpha value is being used not only for blending the RGB values (the background and the penguins), but the alpha values as well, which leaves the surface alpha not == 0xff. They have video running on another plane, and in this rectangle they are seeing video blending. They don't like this. Can you suggest changes to df_andi that will result in no non-0xff alpha values in the display surface? Thanks! -Jack _______________________________________________ directfb-dev mailing list directfb-dev@directfb.org http://mail.directfb.org/cgi-bin/mailman/listinfo/directfb-dev _______________________________________________ directfb-dev mailing list directfb-dev@directfb.org http://mail.directfb.org/cgi-bin/mailman/listinfo/directfb-dev
