Anyway to increase paint performance

[cmessineo]

This is just an experiment I have been doing. It takes about 7 seconds to run with 200 points. The CPU and memory on the machine are not that great 454 MHz ARM9 processor with 128MB RAM, there might not be a way to speed this up, but I thought I'd ask.

void HeatMap::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *)
{
    int x = 0;
    int y = 0;
    qreal intensity = 0;
    qDebug() << QTime::currentTime();
 
    QImage image(m_width, m_height, QImage::Format_ARGB32_Premultiplied);
    QPainter *paint = new QPainter(&image);
 
    foreach (QVariant v, m_data)
    {
        QStringList tmp = v.toString().split(",");
 
        x = tmp[0].toInt();
        y = tmp[1].toInt();
        intensity = tmp[2].toDouble();
        QRadialGradient g(QPointF(x, y), m_radius, QPointF(x, y));
        g.setColorAt(0.0, QColor::fromRgbF(0, 0, 0, intensity));
        g.setColorAt(1.0, QColor::fromRgbF(0, 0, 0, 0.0));
        paint->fillRect(QRectF(x - m_radius, y - m_radius, x + m_radius, y + m_radius), g);
    }
 
    painter->drawImage(QPoint(0, 0), image);
    qDebug() << QTime::currentTime();
}

void HeatMap::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *)
{
    int x = 0;
    int y = 0;
    qreal intensity = 0;
    qDebug() << QTime::currentTime();

    QImage image(m_width, m_height, QImage::Format_ARGB32_Premultiplied);
    QPainter *paint = new QPainter(&image);

    foreach (QVariant v, m_data)
    {
        QStringList tmp = v.toString().split(",");

        x = tmp[0].toInt();
        y = tmp[1].toInt();
        intensity = tmp[2].toDouble();
        QRadialGradient g(QPointF(x, y), m_radius, QPointF(x, y));
        g.setColorAt(0.0, QColor::fromRgbF(0, 0, 0, intensity));
        g.setColorAt(1.0, QColor::fromRgbF(0, 0, 0, 0.0));
        paint->fillRect(QRectF(x - m_radius, y - m_radius, x + m_radius, y + m_radius), g);
    }

    painter->drawImage(QPoint(0, 0), image);
    qDebug() << QTime::currentTime();
}

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Thanks

[wysota]

Do not create the image in the paint() method. In the above method you should only have what is in your line #24.

[anda_skoa]

And it is currently leaking the painter "paint". Just create it on the stack.

Cheers,
_