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Auteur: Dan Dennedy
Datum:  
Aan: Minimalistic plugin API for video effects
Onderwerp: Re: [Frei0r] 5 Cairo based plugins, PATCH 2 - multivalue support
On Monday, November 26, 2012, Janne Liljeblad wrote:

> > We have made an exception for the curves filter's bezier spline and
> > the OpenCV filters' classifiers because there was not an adequate way
> > to do it otherwise.
>
> Why is "curves" using bezier spline instead of Catmull-Rom spline,
> which is industry standard for curves (Gimp, Photoshop, After
> Effects...) and a lot less twitchy? Open Kdenlive and Gimp side by
> side and do some curves manipulations and you'll see what I mean. Does
> anyone have any objections for me creating a filter called "crcurves"
> to provide a Catmull-Rom based curves implementation?



Ok, or add a param to the existing plugin to switch the curve type.


> > It already works for all frei0r double params within MLT and has for a
> > long time. The MLT-frei0r filter bridge is currently using
> > mlt_geometry to accomplish this, but only using the x field of it.
> > Thus, any f0r_param_double (or f0r_param_bool) can be animated in a
> > mlt_property with something like: 0=0.01; 50=0.1; 100=0.5; 500=1.0.
> > Kdenlive has been taking advantage of this capability for a while.
>
> So that happens fully on application/MLT side then. Kdenlive sets "x"
> MLT property value to "0=0.01; 50=0.1" and MLT sets Freior "x" param
> values per frame. Plugin knows nothing of any of this happening, and
> just uses value of x?
>
>

Yes, and also app can provide live preview of param changes. (set refresh=1
property on mlt sdl_preview consumer to make it repaint after property
change.)



> > Sorry, but you need to get rid of frei0r_multivalue.h and make
> > discreet parameters.
>
> So in case of "cairoblend" I'll go from current:
>
>    typedef struct cairo_blend_instance
>   {
>      unsigned int width;
>      unsigned int height;
>      char *opacity;
>      char *blend_mode;
>    } cairo_blend_instance_t;

>
> to:
>
>    typedef struct cairo_blend_instance
>    {
>      unsigned int width;
>      unsigned int height;
>      double opacity; //  this is now F0R_PARAM_DOUBLE;
>      char *blend_mode;
>    } cairo_blend_instance_t;

>
> and just use opacity when drawing:
>
>    double frame_opacity = inst->opacity;

>
> and now if i set "opacity" in Flowblade to "0=0.01; 50=0.1" MLT sets
> correct value to opacity for each frame?
>
> Is this correct?
> _




Correct


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