examples/threads/mandelbrot/renderthread.cpp
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     1 /****************************************************************************
       
     2 **
       
     3 ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
       
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     5 ** Contact: Nokia Corporation (qt-info@nokia.com)
       
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    36 **
       
    37 **
       
    38 ** $QT_END_LICENSE$
       
    39 **
       
    40 ****************************************************************************/
       
    41 
       
    42 #include <QtGui>
       
    43 
       
    44 #include <math.h>
       
    45 
       
    46 #include "renderthread.h"
       
    47 
       
    48 //! [0]
       
    49 RenderThread::RenderThread(QObject *parent)
       
    50     : QThread(parent)
       
    51 {
       
    52     restart = false;
       
    53     abort = false;
       
    54 
       
    55     for (int i = 0; i < ColormapSize; ++i)
       
    56         colormap[i] = rgbFromWaveLength(380.0 + (i * 400.0 / ColormapSize));
       
    57 }
       
    58 //! [0]
       
    59 
       
    60 //! [1]
       
    61 RenderThread::~RenderThread()
       
    62 {
       
    63     mutex.lock();
       
    64     abort = true;
       
    65     condition.wakeOne();
       
    66     mutex.unlock();
       
    67 
       
    68     wait();
       
    69 }
       
    70 //! [1]
       
    71 
       
    72 //! [2]
       
    73 void RenderThread::render(double centerX, double centerY, double scaleFactor,
       
    74                           QSize resultSize)
       
    75 {
       
    76     QMutexLocker locker(&mutex);
       
    77 
       
    78     this->centerX = centerX;
       
    79     this->centerY = centerY;
       
    80     this->scaleFactor = scaleFactor;
       
    81     this->resultSize = resultSize;
       
    82 
       
    83     if (!isRunning()) {
       
    84         start(LowPriority);
       
    85     } else {
       
    86         restart = true;
       
    87         condition.wakeOne();
       
    88     }
       
    89 }
       
    90 //! [2]
       
    91 
       
    92 //! [3]
       
    93 void RenderThread::run()
       
    94 {
       
    95     forever {
       
    96         mutex.lock();
       
    97         QSize resultSize = this->resultSize;
       
    98         double scaleFactor = this->scaleFactor;
       
    99         double centerX = this->centerX;
       
   100         double centerY = this->centerY;
       
   101         mutex.unlock();
       
   102 //! [3]
       
   103 
       
   104 //! [4]
       
   105         int halfWidth = resultSize.width() / 2;
       
   106 //! [4] //! [5]
       
   107         int halfHeight = resultSize.height() / 2;
       
   108         QImage image(resultSize, QImage::Format_RGB32);
       
   109 
       
   110         const int NumPasses = 8;
       
   111         int pass = 0;
       
   112         while (pass < NumPasses) {
       
   113             const int MaxIterations = (1 << (2 * pass + 6)) + 32;
       
   114             const int Limit = 4;
       
   115             bool allBlack = true;
       
   116 
       
   117             for (int y = -halfHeight; y < halfHeight; ++y) {
       
   118                 if (restart)
       
   119                     break;
       
   120                 if (abort)
       
   121                     return;
       
   122 
       
   123                 uint *scanLine =
       
   124                         reinterpret_cast<uint *>(image.scanLine(y + halfHeight));
       
   125                 double ay = centerY + (y * scaleFactor);
       
   126 
       
   127                 for (int x = -halfWidth; x < halfWidth; ++x) {
       
   128                     double ax = centerX + (x * scaleFactor);
       
   129                     double a1 = ax;
       
   130                     double b1 = ay;
       
   131                     int numIterations = 0;
       
   132 
       
   133                     do {
       
   134                         ++numIterations;
       
   135                         double a2 = (a1 * a1) - (b1 * b1) + ax;
       
   136                         double b2 = (2 * a1 * b1) + ay;
       
   137                         if ((a2 * a2) + (b2 * b2) > Limit)
       
   138                             break;
       
   139 
       
   140                         ++numIterations;
       
   141                         a1 = (a2 * a2) - (b2 * b2) + ax;
       
   142                         b1 = (2 * a2 * b2) + ay;
       
   143                         if ((a1 * a1) + (b1 * b1) > Limit)
       
   144                             break;
       
   145                     } while (numIterations < MaxIterations);
       
   146 
       
   147                     if (numIterations < MaxIterations) {
       
   148                         *scanLine++ = colormap[numIterations % ColormapSize];
       
   149                         allBlack = false;
       
   150                     } else {
       
   151                         *scanLine++ = qRgb(0, 0, 0);
       
   152                     }
       
   153                 }
       
   154             }
       
   155 
       
   156             if (allBlack && pass == 0) {
       
   157                 pass = 4;
       
   158             } else {
       
   159                 if (!restart)
       
   160                     emit renderedImage(image, scaleFactor);
       
   161 //! [5] //! [6]
       
   162                 ++pass;
       
   163             }
       
   164 //! [6] //! [7]
       
   165         }
       
   166 //! [7]
       
   167 
       
   168 //! [8]
       
   169         mutex.lock();
       
   170 //! [8] //! [9]
       
   171         if (!restart)
       
   172             condition.wait(&mutex);
       
   173         restart = false;
       
   174         mutex.unlock();
       
   175     }
       
   176 }
       
   177 //! [9]
       
   178 
       
   179 //! [10]
       
   180 uint RenderThread::rgbFromWaveLength(double wave)
       
   181 {
       
   182     double r = 0.0;
       
   183     double g = 0.0;
       
   184     double b = 0.0;
       
   185 
       
   186     if (wave >= 380.0 && wave <= 440.0) {
       
   187         r = -1.0 * (wave - 440.0) / (440.0 - 380.0);
       
   188         b = 1.0;
       
   189     } else if (wave >= 440.0 && wave <= 490.0) {
       
   190         g = (wave - 440.0) / (490.0 - 440.0);
       
   191         b = 1.0;
       
   192     } else if (wave >= 490.0 && wave <= 510.0) {
       
   193         g = 1.0;
       
   194         b = -1.0 * (wave - 510.0) / (510.0 - 490.0);
       
   195     } else if (wave >= 510.0 && wave <= 580.0) {
       
   196         r = (wave - 510.0) / (580.0 - 510.0);
       
   197         g = 1.0;
       
   198     } else if (wave >= 580.0 && wave <= 645.0) {
       
   199         r = 1.0;
       
   200         g = -1.0 * (wave - 645.0) / (645.0 - 580.0);
       
   201     } else if (wave >= 645.0 && wave <= 780.0) {
       
   202         r = 1.0;
       
   203     }
       
   204 
       
   205     double s = 1.0;
       
   206     if (wave > 700.0)
       
   207         s = 0.3 + 0.7 * (780.0 - wave) / (780.0 - 700.0);
       
   208     else if (wave <  420.0)
       
   209         s = 0.3 + 0.7 * (wave - 380.0) / (420.0 - 380.0);
       
   210 
       
   211     r = pow(r * s, 0.8);
       
   212     g = pow(g * s, 0.8);
       
   213     b = pow(b * s, 0.8);
       
   214     return qRgb(int(r * 255), int(g * 255), int(b * 255));
       
   215 }
       
   216 //! [10]