Re: [Lcms-user] Negative channel values are clipped upon floating point conversions to profiles with true gamma TRCs

[Marco F. <Mar...@en...>]

I see, I was assuming pow() being a sqr function :-)

Thanks.

-----Original Message-----
From: Kevin Wheatley [mailto:kev...@gm...] 
Sent: Mittwoch, 17. August 2016 12:39
To: Marco Freudenberger
Cc: LCMS mailing list
Subject: Re: [Lcms-user] Negative channel values are clipped upon floating point conversions to profiles with true gamma TRCs

On Wed, Aug 17, 2016 at 10:21 AM, Marco Freudenberger <Mar...@en...> wrote:
> All,
>
> excuse me, not all that important and I didn't follow the details of the previous discussion.
> I didn't understand why the pow() function might have any issues with negative values.
>         pow(abs(x)) == pow(x)
> or where is my thought mistake?

ignoring the mistake I made with only including the value x and missing the y parameter, the function pow(x, y)

when x is negative and y is not an integer then mathematically you can't represent it as a real number in the general case, that is why it returns NaN see https://en.wikipedia.org/wiki/Exponentiation#Real_exponents_with_negative_bases

Kevin