[FFmpeg-user] Question about "normalize" filter

[Paul B Mahol]

On 1/30/23, Michael Koch <astroelectronic at t-online.de> wrote:
> Am 30.01.2023 um 12:52 schrieb Paul B Mahol:
>> On 1/30/23, Michael Koch <astroelectronic at t-online.de> wrote:
>>> Am 30.01.2023 um 10:29 schrieb Paul B Mahol:
>>>>> You wrote:
>>>>>
>>>>> "With default parameters and just strength(2) set to your values, so
>>>>> the darkest pixels are left  untouched."
>>>>>
>>>>> However I want that black remains untouched. That's not the same,
>>>>> because
>>>>> the darkest pixels in the image aren't black.
>>>>>
>>>>> The workaround is to insert a black pixel before normalizing:
>>>>> -vf drawbox=w=1:h=1:color=black,normalize
>>>> This command produces more convincing output:
>>>>
>>>> -vf colorlevels=rimin=0:gimin=0:bimin=0:rimax=-1:gimax=-1:bimax=-1
>>>>
>>>> this will pick max pixels values from input and stretch it do default
>>>> output max.
>>> This command gives almost the same result as my workaround.
>>> The meaning of -1 for options is missing in the documentation.
>>> It has the same problem as my workaround: The output is only 8-bit.
>>>
>> filter supports up to 16bit rgb(a), adding float would be trivial.
>> patch welcome
>
> Thanks for adding float to colorlevels.
> Is there any filter for gamma correction with float?
> Does the geq filter support float?

Yes.
>
> Michael
>
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