Function av_csp_approximate_trc_gamma

pub unsafe extern "C" fn av_csp_approximate_trc_gamma(trc: u32) -> f64

Determine a suitable ‘gamma’ value to match the supplied AVColorTransferCharacteristic.

See Apple Technical Note TN2257 (https://developer.apple.com/library/mac/technotes/tn2257/_index.html)

This function returns the gamma exponent for the OETF. For example, sRGB is approximated by gamma 2.2, not by gamma 0.45455.

@return Will return an approximation to the simple gamma function matching the supplied Transfer Characteristic, Will return 0.0 for any we cannot reasonably match against.