[IPOL discuss] libpng

[Miguel Colom]

> I think there may have a bug in the 'io_png.c' file provided on IPOL.
> while (ptr_gray < ptr_end)
>>             *ptr_gray++ = (unsigned char) ((6969.f * *ptr_r++
>>                                            + 23434.f * *ptr_g++
>>                                            + 2365.f * *ptr_b++) /
>> 32768.f);

Indeed, I think that to be 100% correct we should apply a round() function
before the (unsigned char) cast to avoid just truncating the value instead
of rounding it to the nearest integer.

Best,
Miguel