Method renderTile

3rdparty/qwt/src/qwt_plot_spectrogram.cpp:572–644

! \brief Render a tile of an image. Rendering in tiles can be used to composite an image in parallel threads. \param xMap X-Scale Map \param yMap Y-Scale Map \param tile Geometry of the tile in image coordinates \param image Image to be rendered */

    \param image Image to be rendered
 */
void QwtPlotSpectrogram::renderTile(
    const QwtScaleMap& xMap, const QwtScaleMap& yMap,
    const QRect& tile, QImage* image ) const
{
    const QwtInterval range = m_data->data->interval( Qt::ZAxis );
    if ( range.width() <= 0.0 )
        return;

    const bool hasGaps = !m_data->data->testAttribute( QwtRasterData::WithoutGaps );

    if ( m_data->colorMap->format() == QwtColorMap::RGB )
    {
        const int numColors = m_data->colorTable.size();
        const QRgb* rgbTable = m_data->colorTable.constData();
        const QwtColorMap* colorMap = m_data->colorMap;

        for ( int y = tile.top(); y <= tile.bottom(); y++ )
        {
            const double ty = yMap.invTransform( y );

            QRgb* line = reinterpret_cast< QRgb* >( image->scanLine( y ) );
            line += tile.left();

            for ( int x = tile.left(); x <= tile.right(); x++ )
            {
                const double tx = xMap.invTransform( x );

                const double value = m_data->data->value( tx, ty );

                if ( hasGaps && qwtIsNaN( value ) )
                {
                    *line++ = 0u;
                }
                else if ( numColors == 0 )
                {
                    *line++ = colorMap->rgb( range, value );
                }
                else
                {
                    const uint index = colorMap->colorIndex( numColors, range, value );
                    *line++ = rgbTable[index];
                }
            }
        }
    }
    else if ( m_data->colorMap->format() == QwtColorMap::Indexed )
    {
        for ( int y = tile.top(); y <= tile.bottom(); y++ )
        {
            const double ty = yMap.invTransform( y );

            unsigned char* line = image->scanLine( y );
            line += tile.left();

            for ( int x = tile.left(); x <= tile.right(); x++ )
            {
                const double tx = xMap.invTransform( x );