QPainter在Qt中支持三种类型的渐变：线性渐变（QLinearGradient）、辐射渐变（QRadialGradient）和锥形渐变（QConicalGradient）。
1，线性渐变（QLinearGradient）
线性渐变由两个控制点定义，连接这两点的线上设置一系列的颜色断点。这些断点被钳位到浮点数0和1之间，0对应第一个控制点，1对应第二个控制点，两个指定断点之间的颜色由线性插值得出。例如：
void MyWidget::paintEvent(QPaintEvent* event) {
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing, true);
QLinearGradient linearGradient(60, 50, 200, 200);
linearGradient.setColorAt(0.2, Qt::white);
linearGradient.setColorAt(0.6, Qt::green);
linearGradient.setColorAt(1.0, Qt::black);
painter.setBrush(QBrush(linearGradient));
painter.drawEllipse(50, 50, 200, 150);
}
这段代码会在一个椭圆内填充从白色到绿色再到黑色的线性渐变。
2，辐射渐变（QRadialGradient）
辐射渐变由一个中心点、半径、一个核心，以及颜色断点控制。中心点和半径定义一个圆，颜色从中心向外扩散。例如：
void MyWidget::paintEvent(QPaintEvent* event) {
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing, true);
QRadialGradient radialGradient(100, 100, 50, Qt::PointF(150, 150), Qt::PointF(150, 150));
radialGradient.setColorAt(0.2, Qt::white);
radialGradient.setColorAt(0.6, Qt::green);
radialGradient.setColorAt(1.0, Qt::black);
painter.setBrush(QBrush(radialGradient));
painter.drawEllipse(50, 50, 200, 150);
}
这段代码会在一个椭圆内填充从中心向外扩散的线性渐变。
3，锥形渐变（QConicalGradient）
锥形渐变由一个中心点和起始角度定义，颜色从中心点向外扩散。例如：
QConicalGradient conicalGradient(100, 100, 45); // 起始角度为45度
conicalGradient.setColorAt(0.1, QColor(128, 138, 135, 150)); // 起始颜色
conicalGradient.setColorAt(0.7, QColor(128, 138, 135, 0)); // 结束颜色
painter.setBrush(conicalGradient); // 设置画刷为锥形渐变
painter.drawEllipse(100, 100, 200, 200); // 在椭圆内绘制锥形渐变效果:ml-citation{ref="1,3" data="citationList"}
:::ml-data{name=citationList}
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