[FFmpeg-devel] [PATCH] IFF: Add grayscale support to decoder

[Sebastian Vater]

Ronald S. Bultje a ?crit :
> Hi,
>
> On Thu, May 13, 2010 at 10:40 AM, Sebastian Vater
> <cdgs.basty at googlemail.com> wrote:
>   
>> So here is an updated version of grayscale support which fixes:
>>
>> 1. Removal of unneeded parenthesis.
>> 2. Changed 'if (count > 0)' to 'if (count)'.
>> 3. Changed '? (extradata_size == 0) : GRAY8 ? PAL8' to '? extradata_size
>> : PAL8 ? GRAY8.
>>     
> [.]
>   
>> +    } else { // PIX_FMT_GRAY8 has no color palette, create one
>> +        uint8_t *gray_pal = (uint8_t *) pal;
>> +        count = 1 << avctx->bits_per_coded_sample;
>> +
>> +        for (i=0; i < count; i++) {
>> +            gray_pal[i] = (i * 255) >> avctx->bits_per_coded_sample;
>> +        }
>> +    }
>>     
>
> Is the palette actually used for GRAY8? I don't think so.
>
>   
You have been correct, for GRAY8 it isn't required!
However, trying out helped me to figure out an error covering grayscale images with
bits_per_coded_sample < 8, since PIX_FMT_GRAY8 is allowed only with bpp == 8.

So this patch fixes this issue by setting PIX_FMT_GRAY8 only if bpp == 8
and initializes a custom RGB color palette for bpp < 8 simulating
correct behaviour (pictures are way too dark otherwise).

Please note that the GRAY2RGB macro will later be used by HAM, too.

I also checked this on big endian and it works correctly there, too.

-- 

Best regards,
                   :-) Basty/CDGS (-:

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