[wswartzendruber]

I've made some modifications. Here's the new help screen:

PQ2HLG 0.1.0
Converts from HDR-PQ (HDR10) to HDR-HLG

USAGE:
    pq2hlg [OPTIONS] <INPUT-FILE> <OUTPUT-FILE> --height <PIXELS> --width <PIXELS>

FLAGS:
        --help       Prints help information
    -V, --version    Prints version information

OPTIONS:
    -h, --height <PIXELS>     Height of the input video stream
    -r, --ref-white <NITS>    Brightness of the input video stream's reference white level [default: 203]
    -w, --width <PIXELS>      Width of the input video stream

ARGS:
    <INPUT-FILE>     Raw input video stream (PQ, Rec.2020, RGB48)
    <OUTPUT-FILE>    Raw output video stream (HLG, Rec.2020, RGB48)

This utility follows the BBC R&D method for converting PQ to HLG. Any pixel brighter than 1,000 nits will be clipped and
no tone mapping will be applied. If a reference white value is supplied, then the input signal will first be linearly
scaled so that the reference white level becomes 203 nits.

I would appreciate someone letting me know if linear scaling for reference white adjustment is the way to go. When it comes to Alita: Battle Angel, I've noticed that the darker areas of the picture are marginally darker than with the native Rec.709 grading from the 1080p Blu-ray. Again, this is when comparing in VLC on a SDR monitor without WCG.

As is the usual case, there are a few more screenshots. These were taken from an HLG encode that uses the new reference white scaling. I sampled the credits and determined that this movie's PQ grading uses 157 nits. So that was linearly scaled up to 203 across all three color channels.

In the future, I intend to add support for Kim-Kautz tone mapping.

EDIT: Imgur Album of Latest Screenshots