From 111558d709d7d55318bdf3de99442f26e246fcdc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Samuel=20R=C3=B8dal?= <sroedal@trolltech.com>
Date: Tue, 13 Oct 2009 18:18:56 +0200
Subject: Optimized bloom graphics effect implementation.

Avoid doing so many conversions by operating on raster pixmaps, and by
using INV_PREMUL/PREMUL instead of converting to ARGB32.

Reviewed-by: Gunnar Sletta
---
 src/gui/effects/qgraphicseffect.cpp | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/src/gui/effects/qgraphicseffect.cpp b/src/gui/effects/qgraphicseffect.cpp
index 01df46d..42845cc 100644
--- a/src/gui/effects/qgraphicseffect.cpp
+++ b/src/gui/effects/qgraphicseffect.cpp
@@ -105,6 +105,7 @@
 #include <QtGui/qpainter.h>
 #include <QtCore/qrect.h>
 #include <QtCore/qdebug.h>
+#include <private/qdrawhelper_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -1461,6 +1462,8 @@ void QGraphicsBloomEffect::setStrength(qreal strength)
     The \a strength parameter holds the effect's new strength.
 */
 
+extern QPixmap qt_toRasterPixmap(const QPixmap &pixmap);
+
 /*!
     \reimp
 */
@@ -1473,26 +1476,27 @@ void QGraphicsBloomEffect::draw(QPainter *painter, QGraphicsEffectSource *source
     }
 
     QPoint offset;
-    QPixmap pixmap = source->pixmap(Qt::DeviceCoordinates, &offset);
-    QImage result = pixmap.toImage().convertToFormat(QImage::Format_ARGB32_Premultiplied);
+    QPixmap pixmap = qt_toRasterPixmap(source->pixmap(Qt::DeviceCoordinates, &offset));
 
     // Blur.
-    QPainter blurPainter(&pixmap);
+    QImage overlay(pixmap.size(), QImage::Format_ARGB32_Premultiplied);
+    overlay.fill(0);
+
+    QPainter blurPainter(&overlay);
     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));
+        const QRgb pixel = INV_PREMUL(bits[i]);
+        bits[i] = PREMUL(qRgba(d->colorTable[qRed(pixel)], d->colorTable[qGreen(pixel)],
+                               d->colorTable[qBlue(pixel)], qAlpha(pixel)));
     }
 
     // Composite.
-    QPainter compPainter(&result);
+    QPainter compPainter(&pixmap);
     compPainter.setCompositionMode(QPainter::CompositionMode_Overlay);
     compPainter.setOpacity(d->strength);
     compPainter.drawImage(0, 0, overlay);
@@ -1500,7 +1504,7 @@ void QGraphicsBloomEffect::draw(QPainter *painter, QGraphicsEffectSource *source
 
     QTransform restoreTransform = painter->worldTransform();
     painter->setWorldTransform(QTransform());
-    painter->drawImage(offset, result);
+    painter->drawImage(offset, pixmap);
     painter->setWorldTransform(restoreTransform);
 }
 
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