Add strength factor to the colorize filter.

To allow fading between the original and the colorized version of the
pixmaps, a new strength factor is introduced, 0.0 means the filter
has no effect at all, 1.0 means full colorization.

Still missing is the non-raster implementation.

Autotest: included
Reviewed-by: Bjørn Erik Nilsen

3 files changed, 94 insertions, 1 deletions

diff --git a/src/gui/image/qpixmapfilter.cpp b/src/gui/image/qpixmapfilter.cpp
index 15704ba..4fa2e6c 100644
--- a/src/gui/image/qpixmapfilter.cpp
+++ b/src/gui/image/qpixmapfilter.cpp
@@ -759,6 +759,10 @@ class QPixmapColorizeFilterPrivate : public QPixmapFilterPrivate
     Q_DECLARE_PUBLIC(QPixmapColorizeFilter)
 public:
     QColor color;
+    qreal strength;
+    quint32 opaque : 1;
+    quint32 alphaBlend : 1;
+    quint32 padding : 30;
 };
 
 /*!
@@ -771,7 +775,11 @@ public:
 QPixmapColorizeFilter::QPixmapColorizeFilter(QObject *parent)
     : QPixmapFilter(*new QPixmapColorizeFilterPrivate, ColorizeFilter, parent)
 {
-    d_func()->color = QColor(0, 0, 192);
+    Q_D(QPixmapColorizeFilter);
+    d->color = QColor(0, 0, 192);
+    d->strength = qreal(1);
+    d->opaque = true;
+    d->alphaBlend = false;
 }
 
 /*!
@@ -797,6 +805,31 @@ void QPixmapColorizeFilter::setColor(const QColor &color)
 }
 
 /*!
+    Gets the strength of the colorize filter, 1.0 means full colorized while
+    0.0 equals to no filtering at all.
+
+    \internal
+*/
+qreal QPixmapColorizeFilter::strength() const
+{
+    Q_D(const QPixmapColorizeFilter);
+    return d->strength;
+}
+
+/*!
+    Sets the strength of the colorize filter to \a strength.
+
+    \internal
+*/
+void QPixmapColorizeFilter::setStrength(qreal strength)
+{
+    Q_D(QPixmapColorizeFilter);
+    d->strength = qBound(qreal(0), strength, qreal(1));
+    d->opaque = !qFuzzyIsNull(d->strength);
+    d->alphaBlend = !qFuzzyIsNull(d->strength - 1);
+}
+
+/*!
     \internal
 */
 void QPixmapColorizeFilter::draw(QPainter *painter, const QPointF &dest, const QPixmap &src, const QRectF &srcRect) const
@@ -807,6 +840,7 @@ void QPixmapColorizeFilter::draw(QPainter *painter, const QPointF &dest, const Q
     QPixmapColorizeFilter *colorizeFilter = static_cast<QPixmapColorizeFilter*>(filter);
     if (colorizeFilter) {
         colorizeFilter->setColor(d->color);
+        colorizeFilter->setStrength(d->strength);
         colorizeFilter->draw(painter, dest, src, srcRect);
         delete colorizeFilter;
         return;
@@ -814,6 +848,11 @@ void QPixmapColorizeFilter::draw(QPainter *painter, const QPointF &dest, const Q
 
     // falling back to raster implementation
 
+    if (!d->opaque) {
+        painter->drawPixmap(dest, src, srcRect);
+        return;
+    }
+
     QImage srcImage;
     QImage destImage;
 
@@ -836,6 +875,16 @@ void QPixmapColorizeFilter::draw(QPainter *painter, const QPointF &dest, const Q
     destPainter.fillRect(srcImage.rect(), d->color);
     destPainter.end();
 
+    if (d->alphaBlend) {
+        // alpha blending srcImage and destImage
+        QImage buffer = srcImage;
+        QPainter bufPainter(&buffer);
+        bufPainter.setOpacity(d->strength);
+        bufPainter.drawImage(0, 0, destImage);
+        bufPainter.end();
+        destImage = buffer;
+    }
+
     if (srcImage.hasAlphaChannel())
         destImage.setAlphaChannel(srcImage.alphaChannel());
 
diff --git a/src/gui/image/qpixmapfilter_p.h b/src/gui/image/qpixmapfilter_p.h
index 4cbf7a3..2565110 100644
--- a/src/gui/image/qpixmapfilter_p.h
+++ b/src/gui/image/qpixmapfilter_p.h
@@ -155,6 +155,9 @@ public:
     void setColor(const QColor& color);
     QColor color() const;
 
+    void setStrength(qreal strength);
+    qreal strength() const;
+
     void draw(QPainter *painter, const QPointF &dest, const QPixmap &src, const QRectF &srcRect = QRectF()) const;
 };
 
diff --git a/tests/auto/qpixmapfilter/tst_qpixmapfilter.cpp b/tests/auto/qpixmapfilter/tst_qpixmapfilter.cpp
index 83bd537..5a9bad7 100644
--- a/tests/auto/qpixmapfilter/tst_qpixmapfilter.cpp
+++ b/tests/auto/qpixmapfilter/tst_qpixmapfilter.cpp
@@ -63,8 +63,10 @@ public slots:
 
 private slots:
     void colorizeSetColor();
+    void colorizeSetStrength();
     void colorizeProcess();
     void colorizeDraw();
+    void colorizeDrawStrength();
     void colorizeDrawSubRect();
     void colorizeProcessSubRect();
     void convolutionBoundingRectFor();
@@ -127,6 +129,16 @@ void tst_QPixmapFilter::colorizeSetColor()
     QCOMPARE(filter.color(), QColor(50, 100, 200));
 }
 
+void tst_QPixmapFilter::colorizeSetStrength()
+{
+    QPixmapColorizeFilter filter;
+    QCOMPARE(filter.strength(), qreal(1));
+    filter.setStrength(0.5);
+    QCOMPARE(filter.strength(), qreal(0.5));
+    filter.setStrength(0.0);
+    QCOMPARE(filter.strength(), qreal(0.0));
+}
+
 void tst_QPixmapFilter::colorizeProcess()
 {
     QPixmapColorizeFilter filter;
@@ -180,6 +192,35 @@ void tst_QPixmapFilter::colorizeDraw()
     }
 }
 
+void tst_QPixmapFilter::colorizeDrawStrength()
+{
+    QPixmapColorizeFilter filter;
+    filter.setColor(Qt::blue);
+    filter.setStrength(0.3);
+
+    QImage source(256, 128, QImage::Format_ARGB32);
+    source.fill(qRgb(255, 0, 0));
+    QPixmap pixmap = QPixmap::fromImage(source);
+
+    QImage result(pixmap.size(), QImage::Format_ARGB32_Premultiplied);
+    QPainter painter(&result);
+    painter.setCompositionMode(QPainter::CompositionMode_Source);
+    filter.draw(&painter, QPointF(0, 0), pixmap);
+    painter.end();
+
+    QImage resultImg = result;
+    for(int y = 0; y < resultImg.height(); y++)
+    {
+        for(int x = 0; x < resultImg.width(); x++)
+        {
+            QRgb pixel = resultImg.pixel(x,y);
+            QCOMPARE(qRed(pixel), 206);
+            QCOMPARE(qGreen(pixel), 26);
+            QCOMPARE(qBlue(pixel), 75);
+        }
+    }
+}
+
 void tst_QPixmapFilter::colorizeDrawSubRect()
 {
     QPixmapColorizeFilter filter;