Kdenlive/Manual/Effects/Alpha manipulation

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Effects - Alpha manipulation

General Information about Alpha Manipulation

Alpha Manipulation, more commonly known as Chroma Key compositing is an effect that changes the background of the picture to a different background the editor may want.

More information can be found on the pages for the effects themselves:

  1. Chroma Key (for simple chroma key effects)
  2. Color Selection (for complex chroma key effects)


Hint for previewing the alpha manipulation effects

The preview in Project monitor might go all strange when you select the composite transition in the timeline or the Video 1 in the timeline. (Reported at bug 2990 and fixed in ver >=0.9.5 of Kdenlive)

Weird preview look.png

This is what the project monitor looks like when you have just selected the composite transition in the timeline. This is not what the rendered video will look like. To get a preview of what the rendered video will look like, you need to click Video 1 and then Video 2 in the timeline.

Two tracks composite transition with alpha info.png

What the preview looks like once you select Video 2 in the timeline. This is what the rendered file will look like



Effects in the Alpha Manipulation Category

  1. Alpha gradient
  2. Alpha operations
  3. Alpha shapes
  4. Chroma Key (for simple chroma key effects)
  5. Color Selection (for complex chroma key effects)
  6. Rectangular Alpha mask (Formerly Mask0Mate)
  7. Rotoscoping
  1. Key Spill Mop Up


Compositing Reference Material

For some background, the Wikipedia article in alpha compositing is useful. See also Porter, Thomas; Tom Duff (1984). "Compositing Digital Images". Computer Graphics 18 (3): p253–259 1984 pdf


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