[kdenlive] Rotoscoping ?

[Jean-Baptiste Mardelle]

On Thursday, July 28, 2016 4:13:44 PM CEST, Nicolas Carion wrote:
> Hi everyone,
>
> In a recent project I wanted to use Rotoscoping, but I was 
> disappointed to see that this feature is unavailable in the 
> recent version provided by my distro (I'm on Arch, they provide 
> 16.04.3). Downgrading is a bit of a mess because it requires 
> downgrading mlt and thus ffmpeg and from there, there is a nasty 
> cascading effect.
>
> Besides the fact that a segfault is a weird way to say 
> "unimplemented feature", especially in a release version, I 
> decided that I could jump in to contribute to add back this 
> feature.
> However, I'm not familiar with the architecture of the project, 
> so I was wondering if someone could point me to the right 
> direction so that I don't loose too much time digging around ?

Hi,

Sorry I didn't take time to handle this sooner.
I now blacklisted rotoscoping for the 16.08 release so the effect will not 
appear anymore in the effect list, preventing the "not supported" crash.

As Vincent explained, the rotoscoping effect was implemented using a 
QGraphicsView (files in src/onmonitoritems/rotoscoping/).

We now have switched to Qml for the monitor overlay, so what is needed is 
to rewrite a qml based canvas that can draw and allow manipulation of 
bezier curves.

I have fixed the crash in git master and added a new qml file that should 
manage this:

data/kdenlivemonitorrotoscene.qml

This qml overlay will be displayed on the monitor when the rotoscoping 
effect is selected. Currently, it is a copy of the corners file, but this 
qml file shoud do the following:

* Kdenlive will send the bezier points in the centerPoints array property, 
and the control points in centerPointsTypes array property.

* From these points, the qml should draw the bezier curve, with control 
points and should allow to move the points and the control points.

* The qml should also allow creating new points.

So if you are interested, any contribution is welcome and I can help you on 
the was.

Regards
jb