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== Effekter - alfamanipulation ==
<span id="Alpha_manipulation"></span>
=== Alfamanipulation ===


=== General Information about Alpha Manipulation ===
<span id="General_Information_about_Alpha_Manipulation"></span>
==== Generel information om alfamanipulation ====  


As far as I am aware Alpha Manipulation effects are always used in combination with a [[Special:myLanguage/Kdenlive/Manual/Transitions/Composite|composite transition]]. This because Alpha Manipulation is to do with manipulating the so called "alpha-channel" of images and videos. The Alpha channel is data that describes how two images are to be combined (or composited) into one. So you need a composite transition on the timeline to tell '''Kdenlive''' that you are compositing the videos from two different tracks into one image.  
Alfamanipulation, almindeligvis kendt som chroma-key compositing, er en effekt, som skifter et billedes baggrund ud med en anden baggrund.


{|
Du kan finde mere information på de enkelte effekters sider:
|[[File:Two tracks no transition.png|left]]||This image shows two video tracks with no transition.<br />The project monitor shows how the upper track takes precedence when no transition is in play.
|}


{|
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Blue Screen|Kroma-key]] (for simple chroma-key-effekter)
|[[File:Two tracks composite transition no alpha info.png|400px|left]]||This image shows two video tracks with a composite transition in place but with no Alpha information to tell '''Kdenlive''' how to combine the images.<br />With composite transition but no alpha info to describe how to composite the picture the top track still takes precedence.
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Color Selection|Farvevalg]] (for komplekse chroma-key-effekter)
|}


{|
|[[File:Two tracks composite transition with alpha info.png|400px|left]]||This image shows the situation with Alpha info now added via the blue screen method.<br />The blue screen effect is also known as "Color to alpha" [http://www.mltframework.org/bin/view/MLT/FilterFrei0r-bluescreen0r] and all the blue screen effect does is say that where the video is blue the alpha value is 0 (i.e. transparent).<br />So now that we have alpha information the second tracks image now shows through where the alpha channel says the image should be transparent.
|}


Once you have some alpha channel data in play you can alter the settings in your [[Special:myLanguage/Kdenlive/Manual/Transitions/Composite|composite transition]] to change how the images will combine. See [[Special:myLanguage/Kdenlive/Manual/Transitions/Composite|composite transition]] page for details.


You can also combine two video tracks together using the [[Special:myLanguage/Kdenlive/Manual/Transitions/screen|screen]] transition (if one of them is filmed on a black background).


=== Hint for previewing the alpha manipulation effects ===
==== Effekter i kategorien Alfamanipulation ====
 
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Alpha gradient|Alfagradient]]
The preview in Project monitor goes all strange when you select the composite transition in the time line or the video 1 in the time line.
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Alpha operations|Alfa-operationer]]
 
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Alpha shapes|Alfaformer]]
[[File:Weird preview look.png|400px|left]]
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Blue Screen|Chroma-key]]
What the project monitor looks like when you have just selected the composite transition in the time line. This is not what the rendered video will look like.
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Color Selection|Farvevalg]]  
To get a look at what the video will render as you need to click Video 1 and then Video 2 in the timeline.
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Mask0Mate|Rektangulær alfamaske]]  
<br style="clear: both;"/>
 
[[File:Two tracks composite transition with alpha info.png|400px|left]] What the preview looks like once you select Video 2 in the timeline. This is what the rendered file will look like
<br style="clear: both;"/>
<br />
 
=== Effects in the Alpha Manipulation Category ===
 
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Alpha gradient|Alpha gradient]]
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Alpha operations|Alpha operations]]
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Alpha shapes|Alpha shapes]]
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Blue Screen|Blue Screen]]
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Color Selection|Color Selection]]
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Mask0Mate|Mask0Mate]]
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Rotoscoping|Rotoscoping]]
# [[Special:myLanguage/Kdenlive/Manual/Effects/Alpha manipulation/Rotoscoping|Rotoscoping]]
# [[Special:myLanguage/Kdenlive/Manual/Effects/Misc/keysplillm0pup|Key Spill Mop Up]]


=== Compositing Reference Material ===
<span id="Compositing_Reference_Material"></span>
==== Baggrundsmateriale om compositing ====


For some background the Wikipedia article in [http://en.wikipedia.org/wiki/Alpha_compositing alpha compositing] is usefull. See also Porter, Thomas; Tom Duff (1984). "Compositing Digital Images". Computer Graphics 18 (3): p253–259 1984 [http://keithp.com/~keithp/porterduff/p253-porter.pdf pdf]
For noget baggrundsinformation (på engelsk) er Wikipediaartiklen  [http://en.wikipedia.org/wiki/Alpha_compositing alpha compositing] nyttig. Se også Porter, Thomas; Tom Duff (1984). "Compositing Digital Images". Computer Graphics 18 (3): p253–259 1984 [http://keithp.com/~keithp/porterduff/p253-porter.pdf pdf]


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[[Category:Kdenlive]]
[[Category:Kdenlive/da]]

Latest revision as of 13:00, 15 August 2023

Other languages:

Alfamanipulation

Generel information om alfamanipulation

Alfamanipulation, almindeligvis kendt som chroma-key compositing, er en effekt, som skifter et billedes baggrund ud med en anden baggrund.

Du kan finde mere information på de enkelte effekters sider:

  1. Kroma-key (for simple chroma-key-effekter)
  2. Farvevalg (for komplekse chroma-key-effekter)



Effekter i kategorien Alfamanipulation

  1. Alfagradient
  2. Alfa-operationer
  3. Alfaformer
  4. Chroma-key
  5. Farvevalg
  6. Rektangulær alfamaske
  7. Rotoscoping
  8. Key Spill Mop Up

Baggrundsmateriale om compositing

For noget baggrundsinformation (på engelsk) er Wikipediaartiklen alpha compositing nyttig. Se også Porter, Thomas; Tom Duff (1984). "Compositing Digital Images". Computer Graphics 18 (3): p253–259 1984 pdf

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