[FFmpeg-user] scaling algorithms

[Paul B Mahol]

On Tue, Sep 21, 2021 at 8:31 AM Michael Koch <astroelectronic at t-online.de>
wrote:

> Am 20.09.2021 um 21:51 schrieb Paul B Mahol:
> > On Sat, Oct 17, 2015 at 3:58 PM Michael Koch <
> astroelectronic at t-online.de>
> > wrote:
> >
> >>   > That looks like the job for the filter, see inflate, deflate,
> erosion
> >> and dilation filters.
> >>
> >> I just tested the dilation filter. It's a nice workaround if the
> >> downscaling factor is 3:1, as in my example. But if the downscaling
> >> factor is smaller, for example from 5472x3648 to 900x600, which is 6:1,
> >> then it fails. The star would be visible in 50% of the frames and
> >> invisible in the other 50%. What I need is a scaling algorithm which
> >> automatically chooses the brightest pixel out of the corresponding
> >> pixels from the input file. If the downscaling factor is 6:1, then the
> >> neighborhood is 6x6 pixels.
> >>
> > See  new morpho filter, that gonna be in master soon.
> >
> > It is much faster than current filters and allow custom definition of
> > structure/mask (rectangle/circle/etc) by using 2nd stream.
>
> That sounds interesting.
> Is the size of the neighborhood over which the filter is working defined
> by the size of the 2nd stream?
>
No, but by structure of pixels which are not 0 in value and are stored in
2nd stream.

So you can use rectangle 6x6 with color=color=white:size=6x6 filter or edit
structure in gimp.


> Which pixel format must be used for the 2nd stream?
>
Anything.

What's the meaning of the pixel values in the 2nd stream? White = pixel
> is used, black = pixel is not used? What happens if a pixel is gray?
> Is the original pixel in the center of the structure or is it the top
> left pixel?
> What's the meaning of "open" and "close"?
> Please add some examples for the structure in the 2nd stream.
>
>
Use google. and learn something about morphological transforms.
FFmpeg can not also educate an uneducated.


> Michael
>
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