nanogui: Doubts regarding Alpha Blending
Subject:
Re: [nanogui] Doubts regarding Alpha Blending
From:
####@####.####
Date:
12 Feb 2003 11:46:04 -0000
Message-Id: <OFEC44BBF4.E740100E-ON80256CCB.003A50CC-80256CCB.003FD0E6@diamond.philips.com>
Hi,
On Wed, 2003-02-12 at 06:32, Vidya Srinivas wrote:
> We need to use Alpha blending for our application. We plan to use Nano-X.
> Could you please tell us what are the necessary steps to be done for
> Nano-x to supoort Alpha blending, or is there any patch to support this
> functionality.
There are two alternative alpha blending patches for Nano-X. One written
by Alex, and one written by me at work (Philips Research). Alex's patch
is available from his CVS, if you want the Philips patch I can send you a
set of diff files.
The Philips patch adds support for a framebuffer in 32-bit with alpha mode
(RGBA). It supports alpha blending when doing any drawing operation - lines
and shapes as well as images. This is needed for interactive TV, such as MHP
(www.mhp.org). It's also useful for implementing Java2D graphics (e.g. J2ME
PBP - Java 2 Micro Edition Personal Basis Profile). However, it doesn't (yet)
have support for alpha blending if the destination isn't a 32-bit display -
it is designed so that this could be added, but it's not something I'm going
to do at work.
Alex's patch is more restricted, but it has the advantage of working now
with (almost?) all display targets. Alex's patch supports drawing images
with a constant alpha or with an alpha map. The nxbreaker demo uses this
to draw images that are semi-transparent and fade out at the edges. AFAICS,
it doesn't support drawing graphics primitives (lines, shapes) with alpha.
Kind regards,
Jon Foster
--
Philips Research Laboratories, Redhill, England
E-mail: ####@####.####
