[PD] color keying using pd and Gem for OSX
cclepper at artic.edu
Sun Jun 22 21:20:17 CEST 2003
> i am having limited success achieving color keying using 2
>stream of video. Have tried using the [pix_alpha] method and can
>achieve color keying using to picture sources
>or using video as the background and an image as the keyed
>foreground, but replacing the foreground image with a movie does not
> tried converting the foreground movie using [pix_rgba] but no
>use, it just screws up the color. using [pix_hsv2rgb] results in
>some sort of keying but not through the pix_alpha method just as a
>result of shifting the color fields around.
> i was wondering if
> a) what i am trying to do is just wrong
> b) some crucial step is missing
> c) GEM implementation on OS X is lacking
which version of GEM are you using? there's not a final release for
OSX yet so you might be using a broken or outdated version. try the
one here: http://taproot.dyndns.org/~cgc/downloads/index.html (make
sure you grab the appropriate one for either G3 or G4 cpu).
it has an object called pix_chroma_key that i wrote and it does
keying on both RGB and YUV sources. it's usage is quite simple it
takes a message for the key 'value' with three arguments for each
color channel, and a 'range' message which is the range of values +/-
the center value.
example for RGB:
value 150 100 50
range 20 10 10
would key using the red channel for a range of 130 to 170 the green
from 90 to 110 and blue 40 to 50. if this was for YUV it would be
the same ranges for Y (luma) Cb (chroma-blue) and Cr (chroma-red) in
there's also a 'direction' message that flips the keyed areas.
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Pd-list