But won't the drawing get affected by the alpha component of the color? I mean if the alpha component of a pixel be 0, wouldn't that pixel be invisible?
-- Sourath
On 12/13/05, Ville Syrjälä <[EMAIL PROTECTED]> wrote:
On Tue, Dec 13, 2005 at 10:11:51PM +0530, Sourath Roy wrote:
> Hi,
> I am using DirectFB-0.9.22 on Linux nVidia(NV32) Framebuffer support(kernel
> 2.6.13).
> On a surface with
> PorterDuff rule set as DSPD_SRC,
> DrawingFlags set to DSDRAW_BLEND, and
> pixelformat set to DSPF_ARGB
>
> I don't see any BLEND effect with varying alpha component of color.
You're using DSPD_SRC so the result is correct.
> For
> example if I do a SetColor with red = 0xff and alpha = 1, and do a
> FillRectangle I see a solid red rectangle. The effect is same as alpha =
> 0xff.
> I observe a change in behavior when I OR the DrawingFlags with
> DSDRAW_SRC_PREMULTIPLY. Then I can see the blend.
Actually you only see the effect of multiplying the source color with
source alpha but you still don't see any blend with the destination.
> Shouldn't the alpha component change impact the drawing without
> DSDRAW_SRC_PREMULTIPLY flag? Because DSDRAW_SRC_PREMULTIPLY forces a change
> in red, green, blue components and thus the effect is seen. Changing alpha
> component alone should make a visible difference, isn't it?
Not with DSPD_SRC. Read the Porter/Duff descriptions in directfb.h.
--
Ville Syrjälä
[EMAIL PROTECTED]
http://www.sci.fi/~syrjala/
_______________________________________________ directfb-users mailing list [email protected] http://mail.directfb.org/cgi-bin/mailman/listinfo/directfb-users
