spectrograph.cpp Example File

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  #include "spectrograph.h"
  #include <QDebug>
  #include <QMouseEvent>
  #include <QPainter>
  #include <QTimerEvent>

  const int NullTimerId = -1;
  const int NullIndex = -1;
  const int BarSelectionInterval = 2000;

  Spectrograph::Spectrograph(QWidget *parent)
      :   QWidget(parent)
      ,   m_barSelected(NullIndex)
      ,   m_timerId(NullTimerId)
      ,   m_lowFreq(0.0)
      ,   m_highFreq(0.0)
  {
      setMinimumHeight(100);
  }

  Spectrograph::~Spectrograph()
  {

  }

  void Spectrograph::setParams(int numBars, qreal lowFreq, qreal highFreq)
  {
      Q_ASSERT(numBars > 0);
      Q_ASSERT(highFreq > lowFreq);
      m_bars.resize(numBars);
      m_lowFreq = lowFreq;
      m_highFreq = highFreq;
      updateBars();
  }

  void Spectrograph::timerEvent(QTimerEvent *event)
  {
      Q_ASSERT(event->timerId() == m_timerId);
      Q_UNUSED(event) // suppress warnings in release builds
      killTimer(m_timerId);
      m_timerId = NullTimerId;
      m_barSelected = NullIndex;
      update();
  }

  void Spectrograph::paintEvent(QPaintEvent *event)
  {
      Q_UNUSED(event)

      QPainter painter(this);
      painter.fillRect(rect(), Qt::black);

      const int numBars = m_bars.count();

      // Highlight region of selected bar
      if (m_barSelected != NullIndex && numBars) {
          QRect regionRect = rect();
          regionRect.setLeft(m_barSelected * rect().width() / numBars);
          regionRect.setWidth(rect().width() / numBars);
          QColor regionColor(202, 202, 64);
          painter.setBrush(Qt::DiagCrossPattern);
          painter.fillRect(regionRect, regionColor);
          painter.setBrush(Qt::NoBrush);
      }

      QColor barColor(51, 204, 102);
      QColor clipColor(255, 255, 0);

      // Draw the outline
      const QColor gridColor = barColor.darker();
      QPen gridPen(gridColor);
      painter.setPen(gridPen);
      painter.drawLine(rect().topLeft(), rect().topRight());
      painter.drawLine(rect().topRight(), rect().bottomRight());
      painter.drawLine(rect().bottomRight(), rect().bottomLeft());
      painter.drawLine(rect().bottomLeft(), rect().topLeft());

      QVector<qreal> dashes;
      dashes << 2 << 2;
      gridPen.setDashPattern(dashes);
      painter.setPen(gridPen);

      // Draw vertical lines between bars
      if (numBars) {
          const int numHorizontalSections = numBars;
          QLine line(rect().topLeft(), rect().bottomLeft());
          for (int i=1; i<numHorizontalSections; ++i) {
              line.translate(rect().width()/numHorizontalSections, 0);
              painter.drawLine(line);
          }
      }

      // Draw horizontal lines
      const int numVerticalSections = 10;
      QLine line(rect().topLeft(), rect().topRight());
      for (int i=1; i<numVerticalSections; ++i) {
          line.translate(0, rect().height()/numVerticalSections);
          painter.drawLine(line);
      }

      barColor = barColor.lighter();
      barColor.setAlphaF(0.75);
      clipColor.setAlphaF(0.75);

      // Draw the bars
      if (numBars) {
          // Calculate width of bars and gaps
          const int widgetWidth = rect().width();
          const int barPlusGapWidth = widgetWidth / numBars;
          const int barWidth = 0.8 * barPlusGapWidth;
          const int gapWidth = barPlusGapWidth - barWidth;
          const int paddingWidth = widgetWidth - numBars * (barWidth + gapWidth);
          const int leftPaddingWidth = (paddingWidth + gapWidth) / 2;
          const int barHeight = rect().height() - 2 * gapWidth;

          for (int i=0; i<numBars; ++i) {
              const qreal value = m_bars[i].value;
              Q_ASSERT(value >= 0.0 && value <= 1.0);
              QRect bar = rect();
              bar.setLeft(rect().left() + leftPaddingWidth + (i * (gapWidth + barWidth)));
              bar.setWidth(barWidth);
              bar.setTop(rect().top() + gapWidth + (1.0 - value) * barHeight);
              bar.setBottom(rect().bottom() - gapWidth);

              QColor color = barColor;
              if (m_bars[i].clipped)
                  color = clipColor;

              painter.fillRect(bar, color);
          }
      }
  }

  void Spectrograph::mousePressEvent(QMouseEvent *event)
  {
      const QPoint pos = event->pos();
      const int index = m_bars.count() * (pos.x() - rect().left()) / rect().width();
      selectBar(index);
  }

  void Spectrograph::reset()
  {
      m_spectrum.reset();
      spectrumChanged(m_spectrum);
  }

  void Spectrograph::spectrumChanged(const FrequencySpectrum &spectrum)
  {
      m_spectrum = spectrum;
      updateBars();
  }

  int Spectrograph::barIndex(qreal frequency) const
  {
      Q_ASSERT(frequency >= m_lowFreq && frequency < m_highFreq);
      const qreal bandWidth = (m_highFreq - m_lowFreq) / m_bars.count();
      const int index = (frequency - m_lowFreq) / bandWidth;
      if (index <0 || index >= m_bars.count())
          Q_ASSERT(false);
      return index;
  }

  QPair<qreal, qreal> Spectrograph::barRange(int index) const
  {
      Q_ASSERT(index >= 0 && index < m_bars.count());
      const qreal bandWidth = (m_highFreq - m_lowFreq) / m_bars.count();
      return QPair<qreal, qreal>(index * bandWidth, (index+1) * bandWidth);
  }

  void Spectrograph::updateBars()
  {
      m_bars.fill(Bar());
      FrequencySpectrum::const_iterator i = m_spectrum.begin();
      const FrequencySpectrum::const_iterator end = m_spectrum.end();
      for ( ; i != end; ++i) {
          const FrequencySpectrum::Element e = *i;
          if (e.frequency >= m_lowFreq && e.frequency < m_highFreq) {
              Bar &bar = m_bars[barIndex(e.frequency)];
              bar.value = qMax(bar.value, e.amplitude);
              bar.clipped |= e.clipped;
          }
      }
      update();
  }

  void Spectrograph::selectBar(int index) {
      const QPair<qreal, qreal> frequencyRange = barRange(index);
      const QString message = QString("%1 - %2 Hz")
                                  .arg(frequencyRange.first)
                                  .arg(frequencyRange.second);
      emit infoMessage(message, BarSelectionInterval);

      if (NullTimerId != m_timerId)
          killTimer(m_timerId);
      m_timerId = startTimer(BarSelectionInterval);

      m_barSelected = index;
      update();
  }