[FFmpeg-devel] [PATCH] libavfi/colorchannelmixer: add sepia tones example to doc

[Paul B Mahol]

On 7/19/13, Lukasz M <lukasz.m.luki at gmail.com> wrote:
>> On 7/17/13, Lukasz Marek <lukasz.m.luki at gmail.com> wrote:
>>> ---
>>>  doc/filters.texi |    5 +++++
>>>  1 files changed, 5 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/doc/filters.texi b/doc/filters.texi
>>> index 785ce85..ac31228 100644
>>> --- a/doc/filters.texi
>>> +++ b/doc/filters.texi
>>> @@ -2371,6 +2371,11 @@ Convert source to grayscale:
>>>  @example
>>>  colorchannelmixer=.3:.4:.3:0:.3:.4:.3:0:.3:.4:.3
>>>  @end example
>>> + at item
>>> +Convert source to sepia tones:
>>> + at example
>>> +colorchannelmixer=.393:.769:.189:0:.349:.686:.168:0:.272:.534:.131
>>
>>
>> How you got this numbers?
>>
>> Red and green could overflow, and blue is not using full scale, max
>> can be 0.937, while idealy it should be 1.
>
> This algorithm is quite popular.
> http://www.techrepublic.com/blog/howdoi/how-do-i-convert-images-to-grayscale-and-sepia-tone-using-c/
> http://stackoverflow.com/questions/1061093/how-is-a-sepia-tone-created
>
> Values that can overflow should be set to max value, which is done
> inside filter.
>
> Best Regards,
> Lukasz Marek
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>

Applied.