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/*************************************************************************
This project implements a complete(!) JPEG (Recommendation ITU-T
T.81 | ISO/IEC 10918-1) codec, plus a library that can be used to
encode and decode JPEG streams.
It also implements ISO/IEC 18477 aka JPEG XT which is an extension
towards intermediate, high-dynamic-range lossy and lossless coding
of JPEG. In specific, it supports ISO/IEC 18477-3/-6/-7/-8 encoding.
Note that only Profiles C and D of ISO/IEC 18477-7 are supported
here. Check the JPEG XT reference software for a full implementation
of ISO/IEC 18477-7.
Copyright (C) 2012-2018 Thomas Richter, University of Stuttgart and
Accusoft. (C) 2019-2020 Thomas Richter, Fraunhofer IIS.
This program is available under two licenses, GPLv3 and the ITU
Software licence Annex A Option 2, RAND conditions.
For the full text of the GPU license option, see README.license.gpl.
For the full text of the ITU license option, see README.license.itu.
You may freely select between these two options.
For the GPL option, please note the following:
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*************************************************************************/
/*
** This file provides a simple TMO that provides fine quality and natural
** look in most cases. It is mostly a global Reinhard operator:
** Erik Reinhard and Kate Devlin. Dynamic Range Reduction Inspired by
** Photoreceptor Physiology. IEEE Transactions on Visualization and
** Computer Graphics (2004).
**
** This is the default TMO for profile C.
**
** $Id: defaulttmoc.cpp,v 1.4 2015/01/20 21:51:49 thor Exp $
**
*/
/// Includes
#include "cmd/defaulttmoc.hpp"
#include "cmd/iohelpers.hpp"
#include "std/stdio.hpp"
#include "std/math.hpp"
///
/// BuildToneMapping_C
// Make a simple attempt to find a reasonable tone mapping from HDR to LDR.
// This is by no means ideal, but seem to work well in most cases.
// The algorithm used here is a simplified version of the exrpptm tone mapper,
// found in the following paper:
// Erik Reinhard and Kate Devlin. Dynamic Range Reduction Inspired by
// Photoreceptor Physiology. IEEE Transactions on Visualization and
// Computer Graphics (2004).
void BuildToneMapping_C(FILE *in,int w,int h,int depth,int count,UWORD tonemapping[65536],
bool flt,bool bigendian,bool xyz,int hiddenbits)
{
long pos = ftell(in);
int x,y,i;
int maxin = 256 << hiddenbits;
double max = (1 << depth) - 1;
double lav = 0.0;
double llav = 0.0;
double minl = HUGE_VAL;
double maxl =-HUGE_VAL;
double miny = HUGE_VAL;
double maxy =-HUGE_VAL;
double m;
long cnt = 0;
for(y = 0;y < h;y++) {
for(x = 0;x < w;x++) {
int r,g,b;
double y;
ReadRGBTriple(in,r,g,b,y,depth,count,flt,bigendian,xyz);
if (y > 0.0) {
double logy = log(y);
lav += y;
llav += logy;
if (logy < minl)
minl = logy;
if (logy > maxl)
maxl = logy;
if (y < miny)
miny = y;
if (y > maxy)
maxy = y;
cnt++;
}
}
}
lav /= cnt;
llav /= cnt;
if (maxl <= minl) {
m = 0.3;
} else {
double k = (maxl - llav) / (maxl - minl);
if (k > 0.0) {
m = 0.3 + 0.7 * pow(k,1.4);
} else {
m = 0.3;
}
}
fseek(in,pos,SEEK_SET);
for(i = 0;i < maxin;i++) {
if (flt) {
double out = i / double(maxin);
double in = pow(pow(lav,m) * out / (1.0 - out),2.2);
if (in < 0.0) in = 0.0;
tonemapping[i] = DoubleToHalf(in);
} else {
double out = i / double(maxin);
double in = max * (miny + (maxy - miny) * pow(lav,m) * out / (1.0 - out));
if (in < 0.0) in = 0.0;
if (in > max) in = max;
tonemapping[i] = in;
}
}
}
///
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