Qt之自定义控件阴影

1.默认阴影

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

2.自定义阴影

customshadoweffect.h

#ifndef CUSTOMSHADOWEFFECT_H#define CUSTOMSHADOWEFFECT_H#include <QGraphicsDropShadowEffect>#include <QGraphicsEffect>class CustomShadowEffect : public QGraphicsEffect{    Q_OBJECTpublic:    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 <QPainter>// #include <QGraphicsEffect>CustomShadowEffect::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_NAMESPACEvoid CustomShadowEffect::draw(QPainter* painter){    // if nothing to show outside the item, just draw source    if ((blurRadius() + distance()) <= 0) {        drawSource(painter);        return;    }    PixmapPadMode mode = QGraphicsEffect::PadToEffectiveBoundingRect;    QPoint offset;    const QPixmap px = sourcePixmap(Qt::DeviceCoordinates, &offset, mode);    // return if no source    if (px.isNull())        return;    // save world transform    QTransform restoreTransform = painter->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.下图是默认和自定义两种情况下作用于按钮的效果

参考链接：https://stackoverflow.com/questions/23718827/qt-shadow-around-window