As far as I know, no such tuorial exists (yet).
Not sure how colour correction is anything to do with alpha channel.
I wrote up what I taught myself about alpha channels gorey details with respect to the alpha shapes effect at
That experience taught me a lot about alpha channel effects. Might be worth a read.
I also curated together 4 tutorials on blue screen at
Selective color adjustments don't need an alpha channel it can just be via a matrix. In terms of using an alpha channel for color correction I think searching mattes and masks will provide some ideas. Your T shirt example, if selective color adjustment is not an option then roto'ing the area or pulling a chromakey matte as a mask and overlay then affect color through the matte.
What would be useful is an adjustment layer like AE and Photoshop and ability to use a mask without another overlay.
Perhaps this is possible already in kdenlive, rarely use color correction in kdenlive as its 8bit. Hopefully MLT GLSL will land soon and speed it up and improve precision and jbm's tracking feature will enable track mattes to be used.
"How about Alphain Alphaout Alphaover alphaxor alphaatop ???"
Dunno anything about them.
Maybe you can write them up when you figure them out. :-)
Some data on these transitions at http://www.mltframework.org/bin/view/MLT/PluginsTransitions
For an explanation of alpha compositing modes see here:
but I think Composite is the mode to use for color correction.
RGB adjustment has an "alpha controlled" option, enabling some secondary correction to be done without compositing.
The guy in the video got it a bit wrong: the "selection on checkers" mode is only intended as a kind of setup and debugging tool, to see where your alpha is transparent and check what the alpha operations are doing, etc.
To see the composite, it should be off - the selected display mode in the alpha operations plugin should be "image".
Also, in Kdenlive the alpha transparency is not automatic, you must add a "composite" transition.
I think there is a bug with the Composite transition : cf. http://kdenlive.org/forum/composite-behaviour-3-tracks
You will not see any thing for alpha effects until you have
1. an alpha channel defined on a clip,
2. Overlapping clips
3. Some sort of transition between them
So you would only expect to see stuff at 60% in you YouTube clip where you have the green,red and alpha in transition.
From my reading of the frieOr doco alphain, alphaover etc transitions are providing the different alpha composting modes - the ones documented in Mario's wiki link. Many of these operations are provided in the composite transition. And are also available from the alpha shapes effect which I think you are using.
If you have a look at the user base article on alpha shapes I mention how the alpha operations modes are only really relevant when you combine multiple alpha channels. The operations define how alpha info from two different tracks are to be combined.
And I am guessing that this also the case with the alphain' alpha or etc transitions.
So you might start to see some effect of the alpha in if you have three tracks - two with alpha shapes on them.
I suspect not too many people use the alphain' alpha or etc because composite does the same things.
But the other thing to note is that preview of alpha effect is for me sometimes dodgy due to what looks like a bug. See the user base article on alpha effects. You might find the result of the alpha compositing different to the preview when you render it.