DGTonemap 1.2
-------------

DGTonemap provides filters for Reinhard and Hable tonemapping operators. This
is a starting point to make available a full HDR->SDR process for Avisynth+.
In the future, I will likely add other operators. Suggestions in this
regard will be appreciated. I will also port it to CUDA.

Requirements
------------

1. Avisynth+ MT recent version
2. avsresize (https://forum.doom9.org/showthread.php?t=173986)
(be sure to get the latest high-performance version r1d)

Reinhard Usage
--------------

DGReinhard(clip, float contrast, float bright)
contrast default: 0.3
bright default: 5.0

Input must be CS_RGBPS, see z_ConvertFormat() in the script below.
If 'clip' is omitted, then as usual implicit last is used.

Higher numbers for bright reduce brightness, you can even go to bright=1000 and beyond,
but it stops having an effect up there.

Hable Usage
--------------

DGHable(clip, float exposure, float a, float b, float c, float d, float e, float f, float w)
exposure default: 2.0
a default: 0.15
b default: 0.50
c default: 0.10
d default: 0.20
e default: 0.02
f default: 0.30
w default: 11.2

Input must be CS_RGBPS, see z_ConvertFormat() in the script below.
If 'clip' is omitted, then as usual implicit last is used.

Meaning of Hable coefficients:

exposure: Gain to apply.
a: Shoulder strength
b: Linear strength
c: Linear angle
d: Toe strength
e: Toe numerator
f: Toe denominator
w: Linear white point

hable(x) = ((x*(a*x+c*b)+d*e) / (x*(a*x+b)+d*f)) - e/f
output_pixel = hable(exposure * input_pixel) / hable(w)

Sample Script
-------------

Following is a sample script for the full HDR->SDR process. The source
UHD video is tonemapped, converted to rec709 colorspace, and downsampled
to 8 bits. To leave it in 16 bits, set pixel_type=YUV420P16 in the second
z_ConvertFormat() call.

loadplugin("DGDecodeNV.dll")
loadplugin("DGTonemap.dll")
loadplugin("avsresize.dll")
SetFilterMTMode("z_ConvertFormat", MT_MULTI_INSTANCE) # May not be needed.
DGSource("THE GREAT WALL.dgi",fulldepth=true)
ConvertBits(10) # Use 12 for 12-bit
z_ConvertFormat(pixel_type="RGBPS",colorspace_op="2020ncl:st2084:2020:l=>rgb:linear:2020:l", dither_type="none")
# Choose one of these:
DGReinhard()
#DGHable()
z_ConvertFormat(pixel_type="YV12",colorspace_op="rgb:linear:2020:l=>709:709:709:l",dither_type="ordered")
prefetch(4)

Copyright (c) 2018 Donald A. Graft, All rights reserved