[FFmpeg-devel] [PATCH 3/4] avutil/pixdesc: add av_pix_fmt_desc_has_alpha()

[Hendrik Leppkes]

 ex

On Thu, Apr 19, 2018 at 9:39 PM, wm4 <nfxjfg at googlemail.com> wrote:
> On Thu, 19 Apr 2018 21:32:20 +0200
> Marton Balint <cus at passwd.hu> wrote:
>
>> Signed-off-by: Marton Balint <cus at passwd.hu>
>> ---
>>  doc/APIchanges      |  3 +++
>>  libavutil/pixdesc.h | 11 +++++++++++
>>  libavutil/version.h |  2 +-
>>  3 files changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/doc/APIchanges b/doc/APIchanges
>> index 4f6ac2a031..2a0b6f057a 100644
>> --- a/doc/APIchanges
>> +++ b/doc/APIchanges
>> @@ -15,6 +15,9 @@ libavutil:     2017-10-21
>>
>>  API changes, most recent first:
>>
>> +2018-04-xx - xxxxxxxxxx - lavu 56.16.100 - pixdesc.h
>> +  Add av_pix_fmt_desc_has_alpha().
>> +
>>  -------- 8< --------- FFmpeg 4.0 was cut here -------- 8< ---------
>>
>>  2018-04-03 - d6fc031caf - lavu 56.13.100 - pixdesc.h
>> diff --git a/libavutil/pixdesc.h b/libavutil/pixdesc.h
>> index 1ab372782a..aef4313ccb 100644
>> --- a/libavutil/pixdesc.h
>> +++ b/libavutil/pixdesc.h
>> @@ -430,4 +430,15 @@ int av_get_pix_fmt_loss(enum AVPixelFormat dst_pix_fmt,
>>  enum AVPixelFormat av_find_best_pix_fmt_of_2(enum AVPixelFormat dst_pix_fmt1, enum AVPixelFormat dst_pix_fmt2,
>>                                               enum AVPixelFormat src_pix_fmt, int has_alpha, int *loss_ptr);
>>
>> +/**
>> + * Return true if a pixel format descriptor has alpha channel.
>> + *
>> + * @param desc the pixel format descriptor
>> + * @return 1 if the pixel format descriptor has alpha, 0 otherwise.
>> + */
>> +static inline int av_pix_fmt_desc_has_alpha(const AVPixFmtDescriptor *desc)
>> +{
>> +    return desc->nb_components == 2 || desc->nb_components == 4 || (desc->flags & AV_PIX_FMT_FLAG_PAL);
>> +}
>
> Good, idea, but...
>
> That doesn't seem very correct. Use AV_PIX_FMT_FLAG_ALPHA? (Although
> PAL8 doesn't have it set, which is probably a bug. Or should have have
> a separate PALA8 format?)
>

I agree, we should be using the flag we already have - and at that
point, we probably also don't need a function to check it?

(The comment above AV_PIX_FMT_FLAG_ALPHA tries to explain the PAL8
case - basically it is unknown if the palette contains alpha or not?
or whatever)

- Hendrik