[PD] GEM - alpha blending of images over movies

[Item State]

thanks for reply, oli. the png is regular 24bit RGB
with alpha channel, not greyscale:

http://sciss.de/test/txtactiLS.png

(the colours are grey but the image is saved RGBA).

i couldn't get the alpha channel to scale using
[pix_alpha]. also the help says, this objects replaced
the alpha channel of a certain input colour, which is
not what i want (i already have 8bit alpha channel and
i want the alpha values to scale. like i have the
white text which is around alpha 80%, i have the
background which is alpha 0%, i have grey underlay
which is around alpha 30%, so when the fade-in is half
done, the pixels need to have alph 40%, alpha 0%,
alpha 15% etc.)

i tried [pix_gain] but it seems to ignore the alpha
channel (see attached gemTest2C.pd).

also for fading to grey, i don't know how to do it.
[pix_contrast] doesn't work, neither changing contrast
nor saturation influences the movie. the same happens
with [pix_rgb2hsv] --> [pix_gain] --> [pix_hsv2rgb].

the movies are encoded quicktime/jpeg since this is
comparably cpu-unintensive. here's an example:

http://sciss.de/test/051_eye1.mov

thanks for your help. ciao, -sciss-



--- Oli44 <oli44 at manga-burgah.net> wrote:

> Le samedi 17 février 2007 à 04:44 +1100, Item State
> a écrit :
> 
> > hi,
> > 
> > i'm trying to port a former jitter patch to pd/gem
> >
>
(http://lists.puredata.info/pipermail/pd-list/2006-11/043853.html).
> > i have problems getting overlayed images to
> display
> > properly. i have four rectangles fed by pix_movie,
> > then i need to fade in and out a rendered text
> image.
> > i tried using pix_image -> pix_texture and [alpha
> 1].
> > the images are .png with transparent portions. i
> once
> > got it to display correctly, but now if i open the
> > patch, the videos all show up with wrong colours:
> > 
> > http://sciss.de/test/Bild%201.png
> > (see attached patch gemTest2.pd)
> > 
> 
> 
> i guess your png pictures are in grayscale and the
> videos not. hence the
> "bug"
> 
> 
> > once i remove the pix_image and pix_texture, save
> the
> > patch and re-open it, the videos show up correctly
> > again:
> > 
> > http://sciss.de/test/Bild%205.png
> > (see attached patch gemTest2B.pd)
> > 
> > ... also, i don't know how to fade in the text
> (the
> > "action" string). is there an alpha-channel
> multiplier
> > for pix_image? thanks for hints!
> > 
> 
> 
> you should add a [pix_alpha] in the render chain and
> send it [ 1
> ( message
> 
> 
> 
> > is it possible to stretch the video so that the
> > rectangle stays the same, but only the top part of
> the
> > video is shown (vertically zoomed without
> > interpolation, so that you can see the pixels)?
> > 
> 
> 
> try the pix_roll object
> 
> 
> > ciao, -sciss-
> 
> 
> ciao
> O.
> 
> 


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