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I was just thinking a bit more about that onion skinning thing for drawings and having the next keyframe's drawing showing through...
It is definitely the way to go ! big_smile

Here's what came out as tentative functionnal specification :

- One drawing is still associated to one and only one key image.
- You can enable/disable fading.
- When enabled, it means each drawing will be seen on a few frames before and after its reference key image.
- The opacity of the drawing peaks on its key image, and is lowered as the play head moves away.
- The default fading value for new drawings is modifiable via general settings.
- Each drawing can have a custom value, modifiable through its configuration window.
- You can disable fading altogether for all drawings if you want.

So far I guess its standard fading / onion skinning and exists in other packages. Now the specific stuff:

- You can set a drawing to have an infinite fading value, meaning it would be visible during all the video.
- It stays linked to its reference key image but it doesn't matter anymore.
- This solves the issue of not being able to have persisting drawings; all without introducing a new set of tools or a new drawing mode...

This also almost solves the custom guides feature:

- Manually draw a circle or more complex shape on the first frame and turn its fading to infinity.
- Save as .kva file.
- import it in another video and you can now move it around, change its color, etc. and use it like a reference frame.
- It won't do all you could expect from a custom guide though, but with some tweaks we could have something very useful, that you can import and resize.
and share with anyone. ( Heck I could even host a repository of custom guides on kinovea.org...)

Opens new horizons !

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Oh, and sorry if this has been proposed by some of you already. I just had to rephrase it with the technical aspects and existing architecture in mind.
Sometimes the same idea needs to come from several people, expressed differently, to provoke insights about its full potential smile

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That sounds awesome!

When flipping through images and checking the faded/ghosted drawing it is especially important to be able to stick to one selected tool. It speeds up the workflow by a lot.