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/****************************************************************************
**
** Copyright (C) 2008-2012 NVIDIA Corporation.
** Copyright (C) 2017 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of Qt 3D Studio.
**
** $QT_BEGIN_LICENSE:GPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 or (at your option) any later version
** approved by the KDE Free Qt Foundation. The licenses are as published by
** the Free Software Foundation and appearing in the file LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#pragma once
#ifndef HDR_H
#define HDR_H
#include "foundation/Qt3DSVec3.h"
//#include "HDR.h"
namespace qt3ds {
class QT3DSVec3;
namespace HDR {
template <int N>
class HDRConfiguration;
template <int N>
class Histogram
{
public:
/**
* @brief build the histogram based on 2^10 binning.
*
* @param[in] inImage Pointer to image
* @param[in] inWidth Width of image
* @param[in] inHeight Height of image
* @param[out] outHistogram
*
* @return No return
*/
static void Build(QT3DSVec3 *inImage, int inWidth, int inHeight, QT3DSVec3 *outHistogram)
{
long noPixels = inWidth * inHeight;
for (int i = 0; i < noPixels; ++i) {
outHistogram[(int)inImage[i].x].x++;
outHistogram[(int)inImage[i].y].y++;
outHistogram[(int)inImage[i].z].z++;
}
}
};
template <int N>
class HDR
{
public:
HDR(HDRConfiguration<N> *inConfiguration) { mHDRConfiguration = inConfiguration; }
void Build(QT3DSVec3 **inImages, int inNoImages, int inWidth, int inHeight, float *inExposures,
QT3DSVec3 *outRadiance)
{
for (int x = 0; x < inWidth; ++x) {
for (int y = 0; y < inHeight; ++y) {
QT3DSVec3 divisor(0.0f);
QT3DSVec3 dividend(0.0f);
for (int i = 0; i < inNoImages; ++i) {
QT3DSVec3 pixel = inImages[i][x + y * inWidth];
dividend += (LUT(mHDRConfiguration->weights, pixel) * inExposures[i])
.multiply(LUT(mHDRConfiguration->CRF, pixel));
divisor += LUT(mHDRConfiguration->weights, pixel) * inExposures[i]
* inExposures[i];
}
divisor.x = 1.0f / divisor.x;
divisor.y = 1.0f / divisor.y;
divisor.z = 1.0f / divisor.z;
outRadiance[x + y * inWidth] = dividend.multiply(divisor);
}
}
}
private:
/**
* @brief Return the value based off from array as a LUT
*
* @param[in] inLUT The LUT table of interest
* @param[in] inValue The value that you have
* @param[out] QT3DSVec3 The corresponding value of array based on input
* tuple
*
* @return No return
*/
QT3DSVec3 LUT(float *inLUT, QT3DSVec3 inValue)
{
return QT3DSVec3(inLUT[(int)inValue.x], inLUT[(int)inValue.y], inLUT[(int)inValue.z]);
}
QT3DSVec3 LUT(QT3DSVec3 *inLUT, QT3DSVec3 inValue)
{
return QT3DSVec3(inLUT[(int)inValue.x].x, inLUT[(int)inValue.y].y,
inLUT[(int)inValue.z].z);
}
HDRConfiguration<N> *mHDRConfiguration;
};
template <int N>
class HDRConfiguration
{
public:
HDRConfiguration()
{
threshold = 0.1f;
maxIterations = 30;
GenerateRobertsonWeighting();
}
void SetCRF(QT3DSVec3 *inCRF) { memcpy(CRF, inCRF, sizeof(QT3DSVec3) * N); }
/**
* @brief build the camera response function
*
* @param[in] inImages Pointer to images
* @param[in] inNoImages Number of images
* @param[in] inWidth Width of image
* @param[in] inHeight Height of image
* @param[out] outHistogram
*
* @return No return
*/
void BuildCRF(QT3DSVec3 **inImages, int inNoImages, int inWidth, int inHeight,
float *inExposures)
{
QT3DSVec3 histogram[N];
QT3DSVec3 newCRF[N];
HDR<N> hdr(this);
memset(histogram, 0, sizeof(QT3DSVec3) * N);
for (int i = 0; i < inNoImages; ++i) {
Histogram<N>::Build(inImages[i], inWidth, inHeight, histogram);
}
for (int i = 0; i < N; ++i) {
histogram[i].x = histogram[i].x > 0 ? 1 / histogram[i].x : 0;
histogram[i].y = histogram[i].y > 0 ? 1 / histogram[i].y : 0;
histogram[i].z = histogram[i].z > 0 ? 1 / histogram[i].z : 0;
}
QT3DSVec3 *radiance = new QT3DSVec3[inWidth * inHeight * sizeof(QT3DSVec3)];
// iteration 0, linearize CRF
for (int i = 0; i < N; ++i) {
CRF[i] = QT3DSVec3((float)i) * 2.0f / N;
}
for (int iteration = 0; iteration < maxIterations; ++iteration) {
hdr.Build(inImages, inNoImages, inWidth, inHeight, inExposures, radiance);
memset(newCRF, 0, sizeof(QT3DSVec3) * N);
for (int i = 0; i < inNoImages; ++i) {
for (int x = 0; x < inWidth; ++x) {
for (int y = 0; y < inHeight; ++y) {
long offset = x + y * inWidth;
QT3DSVec3 pixel = inImages[i][offset];
newCRF[(int)pixel.x].x += (inExposures[i] * radiance[offset].x);
newCRF[(int)pixel.y].y += (inExposures[i] * radiance[offset].y);
newCRF[(int)pixel.z].z += (inExposures[i] * radiance[offset].z);
}
}
}
float difference = 0;
for (int i = 0; i < N; ++i) {
newCRF[i] = newCRF[i].multiply(histogram[i]);
}
QT3DSVec3 middle = newCRF[N / 2];
for (int i = 0; i < N; ++i) {
newCRF[i].x = newCRF[i].x / middle.x;
newCRF[i].y = newCRF[i].y / middle.y;
newCRF[i].z = newCRF[i].z / middle.z;
difference += (CRF[i] - newCRF[i]).magnitude();
}
for (int i = 0; i < N; ++i) {
CRF[i] = newCRF[i];
}
if (difference < threshold) {
break;
}
}
delete[] radiance;
}
float weights[N];
QT3DSVec3 CRF[N];
private:
void GenerateRobertsonWeighting()
{
// Dynamic Range Improvement Through Multiple Exposures (5)
// gaussian random weighting
float divisor = (N - 1) * (N - 1) / 4.0;
for (int i = 0; i < N; ++i) {
float dividend = (i - (N - 1) / 2.0f);
dividend *= dividend;
weights[i] = exp(-4.0f * dividend / divisor);
}
}
int maxIterations;
float threshold;
};
}
}
#endif
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