spectrograph.cpp Example File

multimedia/spectrum/app/spectrograph.cpp
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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(); }

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