Preserve Alpha Channel
In TVPaint Animation, you can also preserve the Alpha channel of a layer.
It is the fourth option on the right of the New button .
You can use this option in order to draw only on the existing pixels of your image. You can also associate this function to shortcuts (search for the 'Preserve Transparency' feature in the Keyboard Shortcuts Configuration panel).
Its use is similar to the Stencils' use, as it lock the existing pixels in the current layer, in order to modify it (changing the color, for example).
Contrary to the Stencils, this function does not affect the other layers, only the current one.
Only the layer with that option enable will be affected.
It allows, for example, to change the colors of your drawings.
Be careful : do not preserve the alpha of an empty layer or turn it into a Stencil! You could not be able to draw anything, without knowing why.