Qt渐变方式显示图片

使用渐变的方式浏览图片，效果如下：

制作的大概思路为使用Qt的属性动画，改变画笔绘制时的透明度，先绘制上一张图片，再绘制要显示的图片。

下面仅贴出本示例的关键代码：

头文件

#include <QPropertyAnimation>

class ImageView : public QWidget
{
    Q_OBJECT
    Q_PROPERTY(float alpha READ alpha WRITE setAlpha)

public:
    ImageView();
    ~ImageView();

private:
    float m_PainterAlpha;
    float alpha(void);
    void setAlpha(float alpha);

    // 背景图片
    QPixmap m_BackgroundPixmap;
    // 动画
    QPropertyAnimation *m_PropertyAnimation = nullptr;
    // 当前要显示的图片
    QPixmap m_CurrentPixmap;

    QWidget *m_ButtonWidget = nullptr;
    QLabel *m_PageTagLabel = nullptr;
    QPushButton *m_PreviousButton = nullptr;
    QPushButton *m_NextButton = nullptr;
}

源文件

#include "BezierCurve.h"
#include <QPainter>
#include <QVBoxLayout>
#include <QColor>
#include <QApplication>
#include <QStyleOption>

BezierCurve::BezierCurve(QWidget *parent)
    :QWidget(parent)
{
    m_SampleCount = 100;

    m_StartColor = QColor(255, 255, 0);
    m_EndColor = QColor(0, 255, 255);

    this->setProperty("NormalWidget", "NormalWidget");
}

BezierCurve::~BezierCurve()
{

}

void BezierCurve::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);

    // 绘制样式
    QStyleOption opt;
    opt.init(this);
    style()->drawPrimitive(QStyle::PE_Widget, &opt, &painter, this);

    painter.setRenderHint(QPainter::Antialiasing, true);

    // 绘制贝塞尔曲线
    drawBezierCurve(&painter, QPointF(20, 20), QPointF(20, 500), QPointF(500, 20), QPointF(500, 500));
    return QWidget::paintEvent(event);
}

void BezierCurve::drawBezierCurve(QPainter* painter, QPointF startPos, QPointF c1, QPointF c2, QPointF endPos)
{
    painter->save();

    QPointF tempPos = startPos;
    for (int i=0; i<=m_SampleCount; ++i)
    {
        // 设置画笔
        QPen pen;
        QColor lineColor = getGradientColor(i);
        pen.setColor(lineColor);
        pen.setWidth(3);
        painter->setPen(pen);

        qreal t = i * 1.0 / m_SampleCount;
        QPointF pos = pow((1 - t), 3) * startPos + \
                      3 * t * pow((1 - t), 2) * c1 + \
                      3 * t * t * (1 - t) * c2 + \
                      pow(t, 3) * endPos;

        // 绘制贝塞尔曲线
        painter->drawLine(tempPos, pos);
        tempPos = pos;
    }

    painter->restore();
}

QColor BezierCurve::getGradientColor(int index)
{
    qreal redInterval = (m_EndColor.red() - m_StartColor.red()) * 1.0 / m_SampleCount;
    qreal greenInterval = (m_EndColor.green() - m_StartColor.green()) * 1.0 / m_SampleCount;
    qreal blueInterval = (m_EndColor.blue() - m_StartColor.blue()) * 1.0 / m_SampleCount;

    QColor gradientColor;
    gradientColor.setRed(redInterval * index + m_StartColor.red());
    gradientColor.setGreen(greenInterval * index + m_StartColor.green());
    gradientColor.setBlue(blueInterval * index + m_StartColor.blue());

    return gradientColor;
}

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