1.默認陰影

QGraphicsDropShadowEffect?*defaultShadow?=?new?QGraphicsDropShadowEffect();
defaultShadow->setBlurRadius(9.0);
defaultShadow->setColor(QColor(0,?0,?0,?160));
defaultShadow->setOffset(4.0);
ui->pushButtonDefault->setGraphicsEffect(defaultShadow);

2.自定義陰影

customshadoweffect.h

#ifndef?CUSTOMSHADOWEFFECT_H
#define?CUSTOMSHADOWEFFECT_H

#include#includeclass?CustomShadowEffect?:?public?QGraphicsEffect
{
????Q_OBJECT
public:
????explicit?CustomShadowEffect(QObject?*parent?=?0);

????void?draw(QPainter*?painter);
????QRectF?boundingRectFor(const?QRectF&?rect)?const;

????inline?void?setDistance(qreal?distance)?{?_distance?=?distance;?updateBoundingRect();?}
????inline?qreal?distance()?const?{?return?_distance;?}

????inline?void?setBlurRadius(qreal?blurRadius)?{?_blurRadius?=?blurRadius;?updateBoundingRect();?}
????inline?qreal?blurRadius()?const?{?return?_blurRadius;?}

????inline?void?setColor(const?QColor&?color)?{?_color?=?color;?}
????inline?QColor?color()?const?{?return?_color;?}

private:
????qreal??_distance;
????qreal??_blurRadius;
????QColor?_color;
};

#endif?//?CUSTOMSHADOWEFFECT_H

customshadoweffect.cpp

#include?"customshadoweffect.h"
#include//?#includeCustomShadowEffect::CustomShadowEffect(QObject?*parent)?:
????QGraphicsEffect(parent),
????_distance(4.0f),
????_blurRadius(10.0f),
????_color(0,?0,?0,?80)
{
}

QT_BEGIN_NAMESPACE
??extern?Q_WIDGETS_EXPORT?void?qt_blurImage(QPainter?*p,?QImage?&blurImage,?qreal?radius,?bool?quality,?bool?alphaOnly,?int?transposed?=?0?);
QT_END_NAMESPACE

void?CustomShadowEffect::draw(QPainter*?painter)
{
????//?if?nothing?to?show?outside?the?item,?just?draw?source
????if?((blurRadius()?+?distance())?worldTransform();
????painter->setWorldTransform(QTransform());

????//?Calculate?size?for?the?background?image
????QSize?szi(px.size().width()?+?2?*?distance(),?px.size().height()?+?2?*?distance());

????QImage?tmp(szi,?QImage::Format_ARGB32_Premultiplied);
????QPixmap?scaled?=?px.scaled(szi);
????tmp.fill(0);
????QPainter?tmpPainter(&tmp);
????tmpPainter.setCompositionMode(QPainter::CompositionMode_Source);
????tmpPainter.drawPixmap(QPointF(-distance(),?-distance()),?scaled);
????tmpPainter.end();

????//?blur?the?alpha?channel
????QImage?blurred(tmp.size(),?QImage::Format_ARGB32_Premultiplied);
????blurred.fill(0);
????QPainter?blurPainter(&blurred);
????qt_blurImage(&blurPainter,?tmp,?blurRadius(),?false,?true);
????blurPainter.end();

????tmp?=?blurred;

????//?blacken?the?image...
????tmpPainter.begin(&tmp);
????tmpPainter.setCompositionMode(QPainter::CompositionMode_SourceIn);
????tmpPainter.fillRect(tmp.rect(),?color());
????tmpPainter.end();

????//?draw?the?blurred?shadow...
????painter->drawImage(offset,?tmp);

????//?draw?the?actual?pixmap...
????painter->drawPixmap(offset,?px,?QRectF());

????//?restore?world?transform
????painter->setWorldTransform(restoreTransform);
}

QRectF?CustomShadowEffect::boundingRectFor(const?QRectF&?rect)?const
{
????qreal?delta?=?blurRadius()?+?distance();
????return?rect.united(rect.adjusted(-delta,?-delta,?delta,?delta));
}

用于Graphics Item

//?...
CustomShadowEffect?*bodyShadow?=?new?CustomShadowEffect();
bodyShadow->setBlurRadius(20.0);
bodyShadow->setDistance(6.0);
bodyShadow->setColor(QColor(0,?0,?0,?80));
item->setGraphicsEffect(bodyShadow);
//?...

用于控件

//...
CustomShadowEffect?*bodyShadow?=?new?CustomShadowEffect();
bodyShadow->setBlurRadius(20.0);
bodyShadow->setDistance(6.0);
bodyShadow->setColor(QColor(0,?0,?0,?80));
ui->widget->setGraphicsEffect(bodyShadow);
//?...

3.下圖是默認和自定義兩種情況下作用于按鈕的效果