Method renderImage

3rdparty/qwt/src/qwt_plot_spectrogram.cpp:480–559

! \brief Render an image from data and color map. For each pixel of area the value is mapped into a color. \param xMap X-Scale Map \param yMap Y-Scale Map \param area Requested area for the image in scale coordinates \param imageSize Size of the requested image \return A QImage::Format_Indexed8 or QImage::Format_ARGB32 depending on the color map. \sa QwtRaste

       QwtColorMap::colorIndex()
 */
QImage QwtPlotSpectrogram::renderImage(
    const QwtScaleMap& xMap, const QwtScaleMap& yMap,
    const QRectF& area, const QSize& imageSize ) const
{
    if ( imageSize.isEmpty() || m_data->data == NULL
        || m_data->colorMap == NULL )
    {
        return QImage();
    }

    const QwtInterval intensityRange = m_data->data->interval( Qt::ZAxis );
    if ( !intensityRange.isValid() )
        return QImage();

    const QImage::Format format = ( m_data->colorMap->format() == QwtColorMap::RGB )
        ? QImage::Format_ARGB32 : QImage::Format_Indexed8;

    QImage image( imageSize, format );

    if ( m_data->colorMap->format() == QwtColorMap::Indexed )
        image.setColorTable( m_data->colorMap->colorTable256() );

    m_data->data->initRaster( area, image.size() );

#if DEBUG_RENDER
    QElapsedTimer time;
    time.start();
#endif

#if !defined( QT_NO_QFUTURE )
    uint numThreads = renderThreadCount();

    if ( numThreads <= 0 )
        numThreads = QThread::idealThreadCount();

    if ( numThreads <= 0 )
        numThreads = 1;

    const int numRows = imageSize.height() / numThreads;

    QVector< QFuture< void > > futures;
    futures.reserve( numThreads - 1 );

    for ( uint i = 0; i < numThreads; i++ )
    {
        QRect tile( 0, i * numRows, image.width(), numRows );
        if ( i == numThreads - 1 )
        {
            tile.setHeight( image.height() - i * numRows );
            renderTile( xMap, yMap, tile, &image );
        }
        else
        {
            futures += QtConcurrent::run(
#if QT_VERSION >= 0x060000
                &QwtPlotSpectrogram::renderTile, this,
#else
                this, &QwtPlotSpectrogram::renderTile,