[FFmpeg-user] Question about "normalize" filter

[Michael Koch]

Hello,

if I understood the documentation correctly, the normalize filter maps 
the darkest input pixel to blackpt and the brightest input pixel to whitept:
darkest pixel --> blackpt
brightest pixel --> whitept

However I need a slightly different mapping:
A black input pixel shall remain black, and the brightest input pixel 
shall become white.
black --> blackpt
brightest pixel --> whitept

With other words: Just multiply all pixels by a suitable constant. Don't 
add or subtract anything.
Is this possible?

Known workaround: Make sure that the input frame contains a black pixel, 
by inserting one in a corner.

Michael