Readd QGraphicsBloomEffect.

This effect was removed in 1c9a28ea64cc53e61a64644dc5a4ff121b475bc5, but
has now been readded on request from a couple of customers. Andreas also
agreed we should provide this effect.

Reviewed-by: Andreas

3 files changed, 224 insertions, 0 deletions

diff --git a/src/gui/effects/qgraphicseffect.cpp b/src/gui/effects/qgraphicseffect.cpp
index eee9bbf..474af53 100644
--- a/src/gui/effects/qgraphicseffect.cpp
+++ b/src/gui/effects/qgraphicseffect.cpp
@@ -67,6 +67,7 @@
     \o QGraphicsOpacityEffect - renders the item with an opacity
     \o QGraphicsPixelizeEffect - pixelizes the item with any pixel size
     \o QGraphicsGrayscaleEffect - renders the item in shades of gray
+    \o QGraphicsBloomEffect - applies a blooming / glowing effect
     \endlist
 
     \img graphicseffect-effects.png
@@ -1305,5 +1306,182 @@ void QGraphicsOpacityEffect::draw(QPainter *painter, QGraphicsEffectSource *sour
     painter->restore();
 }
 
+/*!
+    \class QGraphicsBloomEffect
+    \brief The QGraphicsBloomEffect class provides a bloom/glow effect.
+    \since 4.6
+
+    A bloom/glow effect adds fringes of light around bright areas in the source.
+
+    \img graphicseffect-bloom.png
+
+    \sa QGraphicsDropShadowEffect, QGraphicsBlurEffect, QGraphicsPixelizeEffect,
+        QGraphicsGrayscaleEffect, QGraphicsColorizeEffect
+*/
+
+/*!
+    Constructs a new QGraphicsBloomEffect instance.
+    The \a parent parameter is passed to QGraphicsEffect's constructor.
+*/
+QGraphicsBloomEffect::QGraphicsBloomEffect(QObject *parent)
+    : QGraphicsEffect(*new QGraphicsBloomEffectPrivate, parent)
+{
+    Q_D(QGraphicsBloomEffect);
+    for (int i = 0; i < 256; ++i)
+        d->colorTable[i] = qMin(i + d->brightness, 255);
+}
+
+/*!
+    Destroys the effect.
+*/
+QGraphicsBloomEffect::~QGraphicsBloomEffect()
+{
+}
+
+/*!
+    \reimp
+*/
+QRectF QGraphicsBloomEffect::boundingRectFor(const QRectF &rect) const
+{
+    Q_D(const QGraphicsBloomEffect);
+    const qreal delta = d->blurFilter.radius() * 2;
+    return rect.adjusted(-delta, -delta, delta, delta);
+}
+
+/*!
+    \property QGraphicsBloomEffect::blurRadius
+    \brief the blur radius in pixels of the effect.
+
+    Using a smaller radius results in a sharper appearance, whereas a bigger
+    radius results in a more blurred appearance.
+
+    By default, the blur radius is 5 pixels.
+
+    \sa strength(), brightness()
+*/
+int QGraphicsBloomEffect::blurRadius() const
+{
+    Q_D(const QGraphicsBloomEffect);
+    return d->blurFilter.radius();
+}
+
+void QGraphicsBloomEffect::setBlurRadius(int radius)
+{
+    Q_D(QGraphicsBloomEffect);
+    if (d->blurFilter.radius() == radius)
+        return;
+
+    d->blurFilter.setRadius(radius);
+    updateBoundingRect();
+    emit blurRadiusChanged(radius);
+}
+
+/*!
+    \property QGraphicsBloomEffect::brightness
+    \brief the brightness of the glow.
+
+    The value should be in the range of 0 to 255, where 0 is dark
+    and 255 is bright.
+
+    By default, the brightness is 70.
+
+    \sa strength(), blurRadius()
+*/
+int QGraphicsBloomEffect::brightness() const
+{
+    Q_D(const QGraphicsBloomEffect);
+    return d->brightness;
+}
+
+void QGraphicsBloomEffect::setBrightness(int brightness)
+{
+    Q_D(QGraphicsBloomEffect);
+    brightness = qBound(0, brightness, 255);
+    if (d->brightness == brightness)
+        return;
+
+    d->brightness = brightness;
+    for (int i = 0; i < 256; ++i)
+        d->colorTable[i] = qMin(i + brightness, 255);
+
+    update();
+    emit brightnessChanged(brightness);
+}
+
+/*!
+    \property QGraphicsBloomEffect::strength
+    \brief the strength of the effect.
+
+    A strength 0.0 equals to no effect, while 1.0 means maximum glow.
+
+    By default, the strength is 0.7.
+*/
+qreal QGraphicsBloomEffect::strength() const
+{
+    Q_D(const QGraphicsBloomEffect);
+    return d->strength;
+}
+
+void QGraphicsBloomEffect::setStrength(qreal strength)
+{
+    Q_D(QGraphicsBloomEffect);
+    strength = qBound(qreal(0.0), strength, qreal(1.0));
+    if (qFuzzyCompare(d->strength, strength))
+        return;
+
+    d->strength = strength;
+    update();
+    emit strengthChanged(strength);
+}
+
+/*!
+    \reimp
+*/
+void QGraphicsBloomEffect::draw(QPainter *painter, QGraphicsEffectSource *source)
+{
+    Q_D(QGraphicsBloomEffect);
+    if (d->strength < 0.001) {
+        source->draw(painter);
+        return;
+    }
+
+    const Qt::CoordinateSystem system = source->isPixmap()
+                                        ? Qt::LogicalCoordinates : Qt::DeviceCoordinates;
+    QPoint offset;
+    QPixmap pixmap = source->pixmap(system, &offset);
+    QImage result = pixmap.toImage().convertToFormat(QImage::Format_ARGB32_Premultiplied);
+
+    // Blur.
+    QPainter blurPainter(&pixmap);
+    d->blurFilter.draw(&blurPainter, QPointF(), pixmap);
+    blurPainter.end();
+
+    // Brighten.
+    QImage overlay = pixmap.toImage().convertToFormat(QImage::Format_ARGB32);
+    const int numBits = overlay.width() * overlay.height();
+    QRgb *bits = reinterpret_cast<QRgb *>(overlay.bits());
+    for (int i = 0; i < numBits; ++i) {
+        const QRgb bit = bits[i];
+        bits[i] = qRgba(d->colorTable[qRed(bit)], d->colorTable[qGreen(bit)],
+                        d->colorTable[qBlue(bit)], qAlpha(bit));
+    }
+
+    // Composite.
+    QPainter compPainter(&result);
+    compPainter.setCompositionMode(QPainter::CompositionMode_Overlay);
+    compPainter.setOpacity(d->strength);
+    compPainter.drawImage(0, 0, overlay);
+    compPainter.end();
+
+    if (system == Qt::DeviceCoordinates) {
+        QTransform restoreTransform = painter->worldTransform();
+        painter->setWorldTransform(QTransform());
+        painter->drawImage(offset, result);
+        painter->setWorldTransform(restoreTransform);
+    } else {
+        painter->drawImage(offset, result);
+    }
+}
+
 QT_END_NAMESPACE
 
diff --git a/src/gui/effects/qgraphicseffect.h b/src/gui/effects/qgraphicseffect.h
index c256381..c2bb9b0 100644
--- a/src/gui/effects/qgraphicseffect.h
+++ b/src/gui/effects/qgraphicseffect.h
@@ -339,6 +339,40 @@ private:
     Q_DISABLE_COPY(QGraphicsOpacityEffect)
 };
 
+class QGraphicsBloomEffectPrivate;
+class Q_GUI_EXPORT QGraphicsBloomEffect: public QGraphicsEffect
+{
+    Q_OBJECT
+    Q_PROPERTY(int blurRadius READ blurRadius WRITE setBlurRadius NOTIFY blurRadiusChanged)
+    Q_PROPERTY(int brightness READ brightness WRITE setBrightness NOTIFY brightnessChanged)
+    Q_PROPERTY(qreal strength READ strength WRITE setStrength NOTIFY strengthChanged)
+public:
+    QGraphicsBloomEffect(QObject *parent = 0);
+    ~QGraphicsBloomEffect();
+
+    QRectF boundingRectFor(const QRectF &rect) const;
+    int blurRadius() const;
+    int brightness() const;
+    qreal strength() const;
+
+public Q_SLOTS:
+    void setBlurRadius(int blurRadius);
+    void setBrightness(int brightness);
+    void setStrength(qreal strength);
+
+Q_SIGNALS:
+    void blurRadiusChanged(int blurRadius);
+    void brightnessChanged(int brightness);
+    void strengthChanged(qreal strength);
+
+protected:
+    void draw(QPainter *painter, QGraphicsEffectSource *source);
+
+private:
+    Q_DECLARE_PRIVATE(QGraphicsBloomEffect)
+    Q_DISABLE_COPY(QGraphicsBloomEffect)
+};
+
 QT_END_NAMESPACE
 
 QT_END_HEADER
diff --git a/src/gui/effects/qgraphicseffect_p.h b/src/gui/effects/qgraphicseffect_p.h
index e109790..96eda0e 100644
--- a/src/gui/effects/qgraphicseffect_p.h
+++ b/src/gui/effects/qgraphicseffect_p.h
@@ -185,6 +185,18 @@ public:
     uint hasOpacityMask : 1;
 };
 
+class QGraphicsBloomEffectPrivate : public QGraphicsEffectPrivate
+{
+    Q_DECLARE_PUBLIC(QGraphicsBlurEffect)
+public:
+    QGraphicsBloomEffectPrivate() : brightness(70), strength(0.7) {}
+
+    QPixmapBlurFilter blurFilter;
+    int colorTable[256];
+    int brightness;
+    qreal strength;
+};
+
 QT_END_NAMESPACE
 
 #endif // QGRAPHICSEFFECT_P_H