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// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
#include "renderthread.h"
#include <QImage>
#include <QElapsedTimer>
#include <QTextStream>
#include <cmath>
int RenderThread::numPasses = 8;
//! [0]
RenderThread::RenderThread(QObject *parent)
: QThread(parent)
{
for (int i = 0; i < ColormapSize; ++i)
colormap[i] = rgbFromWaveLength(380.0 + (i * 400.0 / ColormapSize));
}
//! [0]
//! [1]
RenderThread::~RenderThread()
{
mutex.lock();
abort = true;
condition.wakeOne();
mutex.unlock();
wait();
}
//! [1]
//! [2]
void RenderThread::render(double centerX, double centerY, double scaleFactor,
QSize resultSize, double devicePixelRatio)
{
QMutexLocker locker(&mutex);
this->centerX = centerX;
this->centerY = centerY;
this->scaleFactor = scaleFactor;
this->devicePixelRatio = devicePixelRatio;
this->resultSize = resultSize;
if (!isRunning()) {
start(LowPriority);
} else {
restart = true;
condition.wakeOne();
}
}
//! [2]
//! [3]
void RenderThread::run()
{
QElapsedTimer timer;
forever {
mutex.lock();
const double devicePixelRatio = this->devicePixelRatio;
const QSize resultSize = this->resultSize * devicePixelRatio;
const double requestedScaleFactor = this->scaleFactor;
const double scaleFactor = requestedScaleFactor / devicePixelRatio;
const double centerX = this->centerX;
const double centerY = this->centerY;
mutex.unlock();
//! [3]
//! [4]
const int halfWidth = resultSize.width() / 2;
//! [4] //! [5]
const int halfHeight = resultSize.height() / 2;
QImage image(resultSize, QImage::Format_RGB32);
image.setDevicePixelRatio(devicePixelRatio);
int pass = 0;
while (pass < numPasses) {
const int MaxIterations = (1 << (2 * pass + 6)) + 32;
constexpr int Limit = 4;
bool allBlack = true;
timer.restart();
for (int y = -halfHeight; y < halfHeight; ++y) {
if (restart)
break;
if (abort)
return;
auto scanLine =
reinterpret_cast<uint *>(image.scanLine(y + halfHeight));
const double ay = centerY + (y * scaleFactor);
for (int x = -halfWidth; x < halfWidth; ++x) {
const double ax = centerX + (x * scaleFactor);
double a1 = ax;
double b1 = ay;
int numIterations = 0;
do {
++numIterations;
const double a2 = (a1 * a1) - (b1 * b1) + ax;
const double b2 = (2 * a1 * b1) + ay;
if ((a2 * a2) + (b2 * b2) > Limit)
break;
++numIterations;
a1 = (a2 * a2) - (b2 * b2) + ax;
b1 = (2 * a2 * b2) + ay;
if ((a1 * a1) + (b1 * b1) > Limit)
break;
} while (numIterations < MaxIterations);
if (numIterations < MaxIterations) {
*scanLine++ = colormap[numIterations % ColormapSize];
allBlack = false;
} else {
*scanLine++ = qRgb(0, 0, 0);
}
}
}
if (allBlack && pass == 0) {
pass = 4;
} else {
if (!restart) {
QString message;
QTextStream str(&message);
str << " Pass " << (pass + 1) << '/' << numPasses
<< ", max iterations: " << MaxIterations << ", time: ";
const auto elapsed = timer.elapsed();
if (elapsed > 2000)
str << (elapsed / 1000) << 's';
else
str << elapsed << "ms";
image.setText(infoKey(), message);
emit renderedImage(image, requestedScaleFactor);
}
//! [5] //! [6]
++pass;
}
//! [6] //! [7]
}
//! [7]
//! [8]
mutex.lock();
//! [8] //! [9]
if (!restart)
condition.wait(&mutex);
restart = false;
mutex.unlock();
}
}
//! [9]
//! [10]
uint RenderThread::rgbFromWaveLength(double wave)
{
double r = 0;
double g = 0;
double b = 0;
if (wave >= 380.0 && wave <= 440.0) {
r = -1.0 * (wave - 440.0) / (440.0 - 380.0);
b = 1.0;
} else if (wave >= 440.0 && wave <= 490.0) {
g = (wave - 440.0) / (490.0 - 440.0);
b = 1.0;
} else if (wave >= 490.0 && wave <= 510.0) {
g = 1.0;
b = -1.0 * (wave - 510.0) / (510.0 - 490.0);
} else if (wave >= 510.0 && wave <= 580.0) {
r = (wave - 510.0) / (580.0 - 510.0);
g = 1.0;
} else if (wave >= 580.0 && wave <= 645.0) {
r = 1.0;
g = -1.0 * (wave - 645.0) / (645.0 - 580.0);
} else if (wave >= 645.0 && wave <= 780.0) {
r = 1.0;
}
double s = 1.0;
if (wave > 700.0)
s = 0.3 + 0.7 * (780.0 - wave) / (780.0 - 700.0);
else if (wave < 420.0)
s = 0.3 + 0.7 * (wave - 380.0) / (420.0 - 380.0);
r = std::pow(r * s, 0.8);
g = std::pow(g * s, 0.8);
b = std::pow(b * s, 0.8);
return qRgb(int(r * 255), int(g * 255), int(b * 255));
}
//! [10]
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