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Windows Movie Maker  > Transitions, Effects and Titles  > Re: A method to create Chroma key and Transparency    
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 Author Thread: A method to create Chroma key and Transparency
dlk is not online. Last active: 7/2/2011 1:14:29 PM dlk
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Joined: 11 Sep 2004
Total Posts: 2027
 
A method to create Chroma key and Transparency
Posted: 19 Nov 2004 09:07 PM
I have devised a way to combine chroma key and
transparency at the same time. I have searched
and searched for effects/transitions that would
do this, without luck. So this is more of a multi-step
process using known transitions and effect. This is not
a perfect effect...I get some antialiasing around
oval images, and I get some color shards(for
lack of a technical term). But...perhaps if you
use a high quality GIF or PNG image, you might
get very nice results.
So...what am I talking about? If someone
has a website to display 2 samples, I can show
you what I mean.
Basically...there are 2 flavors.
#1. An image overlayed and transparent onto your
movie. My testing was with a geometric image(circle,
rectangle, triangle),but I think it may work with other
images. This could be used to create a transparent
rectangle, and then add some text...(think Monday
Night football oval, without the player of course)
#2. An animated GIF overlayed on your movie...
with transparency. This uses a variation of
Rehan's PIP transitions...so the location would be
in a specific corner...top, side... whatever.

Now, the details are pretty lengthy(not difficult)...so
I won't go into unless someone actually thinks this
is worth filling the space.

dlk

Rehan is not online. Last active: 5/8/2012 5:49:17 PM Rehan
www.rehanfx.org
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Joined: 21 Apr 2004
Total Posts: 2176
 
Re: A method to create Chroma key and Transparency
Posted: 20 Nov 2004 12:57 AM
There are various websites including www.fotki.com and www.pbase.com that allow temporary/limited image hosting for free.

Otherwis you can send me the images (support @ rehanfx.org) and I will put them on somewhere to view.

But important question is how does your method differ from the standard chroma keying as discussed before? Are the results of standard method not acceptable?

www.rehanfx.org - do more with Windows Movie Maker...
rehanfx.x10hosting.com - mirror site
dlk is not online. Last active: 7/2/2011 1:14:29 PM dlk
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Joined: 11 Sep 2004
Total Posts: 2027
 
Re: A method to create Chroma key and Transparency
Posted: 20 Nov 2004 01:02 AM
We need the abilitiy to edit our posts...so we can rewrite history.
Obviously, I meant the image can suffer from aliasing(jaggies),
something fixed with antialiasing. Please excuse this, and
any other mistakes my fat fingers my have typed.

dlk
dlk is not online. Last active: 7/2/2011 1:14:29 PM dlk
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Joined: 11 Sep 2004
Total Posts: 2027
 
Re: A method to create Chroma key and Transparency
Posted: 20 Nov 2004 01:29 AM
Well, my method uses the standard chromakey methods
already discussed, but the image is transparent. For
example ......

__________
|.........b.......|
|..................|
|...b....I....b..|
|..................|
|........b........|
|_________|

In this attempt to visualize the results,
b is the background video, and I is
the image chroma keyed over the
video. My method allows I to be
transparent, so you can see the
video moving through and behind it.
Now...if this is part of the standard
chroma method...I missed that, and
would like to know how to do it the
easy way...cause my method is
a bit tedious


dlk
me1of6 is not online. Last active: 8/5/2005 3:45:14 PM me1of6
Joined: 19 Nov 2004
Total Posts: 8
 
Re: A method to create Chroma key and Transparency
Posted: 20 Nov 2004 02:47 AM
Can you do the opposite? Can you create a still background and allow the moving video to be transparent? Meaning you can see through the moving video to the background? I can see it in my head, I have tried to make the effect with brightness and contrast, but it is only lighter, not transparent.
Rehan is not online. Last active: 5/8/2012 5:49:17 PM Rehan
www.rehanfx.org
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Joined: 21 Apr 2004
Total Posts: 2176
 
Re: A method to create Chroma key and Transparency
Posted: 20 Nov 2004 03:06 AM
dlk,
Yes that is what the standard chroma key method does. Lets suppose we have a clip A and a still image B. The image B is to be overlayed on to A so that a particular region of B becomes completely transparent showing through the underlying portions of clip A.

The portion of B that becomes transparent is specified by the "key" color value. For example if we choose black as the key color then all pixels in B having black would become completely transparent. The non-black color area of B is shown on top of A.

This works pretty well if one makes sure that image B is prepared exactly i.e. the area to be made transparent is exactly the key color. Even a single value of R, G or B different from key can make it non-transparent. Also the size needs to match exactly to the output size. That is why it doesnt show properly sometimes in the preview which is rendered in lower resolution (always 320x240 for ntsc).

Also antialiasing causes trouble. Since the pixels in the region where antialiasing blends neighbouring pixels, the background colors gets mixed with other colors thus causing the chroma keying to fail.

There is some confusion about this method failing with animated gifs. I have had mixed results so far and am investigating as to why it fails.


www.rehanfx.org - do more with Windows Movie Maker...
rehanfx.x10hosting.com - mirror site
dlk is not online. Last active: 7/2/2011 1:14:29 PM dlk
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Joined: 11 Sep 2004
Total Posts: 2027
 
Re: A method to create Chroma key and Transparency
Posted: 20 Nov 2004 08:42 AM
Rehan,
In your explanation above...you say:
"All pixels in B having black would become completely
transparent. The non-black color area of B is shown
on top of A"

With my process...
The non-black color area of B is transparent
and A can be seen underneath"
Yet still...
All pixels in B having black would still be
completely transparent


DLK
dlk is not online. Last active: 7/2/2011 1:14:29 PM dlk
Top 25 Poster
Joined: 11 Sep 2004
Total Posts: 2027
 
Re: A method to create Chroma key and Transparency
Posted: 20 Nov 2004 08:59 AM
Me1of6,
What you want is doable. It has been described
on this message board a couple of times.
Rehan has created a transition called "overlay"
It has also been called translucency.
This is not my creation...but this should
work for you. .2 and .5 gives you 2 different levels of
translucency. Change the progess value to fit your needs.
(I happen to use this transition in one of the
step for creating transparent chroma key.)


<TransitionsAndEffects Version="1.0">
<Transitions>
<TransitionDLL guid="{16B280C5-EE70-11D1-9066-00C04FD9189D}">
<Transition name="Translucent 0.5" iconid="12" >
<Param name="Progress" value="0.5" />
</Transition>
</TransitionDLL>
<TransitionDLL guid="{16B280C5-EE70-11D1-9066-00C04FD9189D}">
<Transition name="Translucent 0.2" iconid="12" >
<Param name="Progress" value="0.2" />
</Transition>
</TransitionDLL>
</Transitions>
</TransitionsAndEffects>












me1of6 is not online. Last active: 8/5/2005 3:45:14 PM me1of6
Joined: 19 Nov 2004
Total Posts: 8
 
Re: A method to create Chroma key and Transparency
Posted: 20 Nov 2004 04:33 PM
AWESOME!!!!......LOVE IT...........Thanks a ton!!!
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