[MPlayer-dev-eng] Re: New remove-logo filter

[Ivo]

On Saturday 26 February 2005 03:39, Trent Piepho wrote:
> On Fri, 25 Feb 2005, Reimar Döffinger wrote:
> > ppm for color + pgm for alpha. And yes, it is possible to create this
> > with gimp (or in the worst case with tifftopnm), the other way round
>
> Automatically with the gimp?  My gimp doesn't have that option.  I guess
> you have to extract the alpha somehow and save it separately, I'm not a
> gimp expert.

Remember, you don't start with a rgba png image. You start with a black 
frame with the logo on it; a screen capture. If you can make a rgba png 
from that, you can also make a ppm and pgm file from that. In fact, the 
latter is easier:

Load the rgb screen capture
Set mode to greyscale
Save as pgm
Close image
Load the rgb screen capture
Select all non-black pixels and fill with white
Save as ppm

If you use -vo pnm:pgm to capture the frame, it's even simpler.

Anyway, I believe this is in the wrong thread. The remove_logo filter only 
needs an on/off bitmap (which, if i read the code correctly, can be the 
alpha channel; all non-zero pixels are treated as pixels to be blurred). 
But, the above procedure should be correct for the deblendlogo filter. So, 
both filters should read a pgm alpha channel and one of them (the deblend 
one) should also read a ppm.

For collored logo's, the procedure is slightly different (only for deblend), 
but still not complicated.

--Ivo