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

Lukasz M lukasz.m.luki at gmail.com
Fri Jul 19 12:43:23 CEST 2013


> 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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