渐变,是指逐渐的,有规律性的变化,是一种规律性很强的现象。
Qt提供了一个与渐变相关的QGradient类,目前支持三种渐变画刷,
分别是线性渐变(QLinearGradient)、辐射渐变(QRadialGradient)、角度渐变(QConicalGradient),
如下图所示:
代码如下:
/*---------------头函数-----------------*/
#ifndef GRADIENT_TEST_H
#define GRADIENT_TEST_H
#include<QWidget>
#include<QPainter>
#include<QStyleOption>
#include<QResizeEvent>
class gradient_test:public QWidget
{
Q_OBJECT
public:
explicit gradient_test(QWidget*parent=0);
virtual QSize sizeHint()const;
protected:
void paintEvent(QPaintEvent*event);
void resizeEvent(QResizeEvent*event);
private:
QSize initSize;
QImage newSize;
void drawLine(const QSize&newSize);
};
/*---------------原函数-----------------*/
#endif//GRADIENT_TEST_H
#include "widget.h"
gradient_test::gradient_test(QWidget*parent)
:QWidget(parent),initSize(300,300)
{
resize(650,250); //窗口大小
}
void gradient_test::drawLine(const QSize& initSize)
{
QPainter painter(&newSize); //wheel作为画图对象?
painter.setRenderHint(QPainter::Antialiasing); //消除锯齿
newSize.fill(Qt::white);
//线性渐变
QLinearGradient linearGradient(0,0,330,330);
//创建了一个QLinearGradient对象实例,参数为起点和终点坐标,可作为颜色渐变的方向
//painter.setPen(Qt::NoPen);
linearGradient.setColorAt(0.0,Qt::green);
linearGradient.setColorAt(0.2,Qt::white);
linearGradient.setColorAt(0.4,Qt::blue);
linearGradient.setColorAt(0.6,Qt::red);
linearGradient.setColorAt(1.0,Qt::yellow);
painter.setBrush(QBrush(linearGradient));
painter.drawRect(10,10,200,200);
//前面为左边,后面两个参数为横轴和纵轴,上面的四行分别设置渐变的颜色和路径比例
//辐射渐变
QRadialGradient radialGradient(310,110,100,310,110);
//创建了一个QRadialGradient对象实例,参数分别为中心坐标,半径长度和焦点坐标,如果需要对称那么中心坐标和焦点坐标要一致
radialGradient.setColorAt(0,Qt::green);
radialGradient.setColorAt(0.2,Qt::white);
radialGradient.setColorAt(0.4,Qt::blue);
radialGradient.setColorAt(0.6,Qt::red);
radialGradient.setColorAt(1.0,Qt::yellow);
painter.setBrush(QBrush(radialGradient));
painter.drawRect(210,10,200,200);//在相应的坐标画出来
//弧度渐变
QConicalGradient conicalGradient(510,110,0);
//创建了一个QConicalGradient对象实例,参数分别为中心坐标和初始角度
conicalGradient.setColorAt(0,Qt::green);
conicalGradient.setColorAt(0.2,Qt::white);
conicalGradient.setColorAt(0.4,Qt::blue);
conicalGradient.setColorAt(0.6,Qt::red);
conicalGradient.setColorAt(0.8,Qt::yellow);
conicalGradient.setColorAt(1.0,Qt::green);
//设置渐变的颜色和路径比例
painter.setBrush(QBrush(conicalGradient));
painter.drawRect(410,10,200,200);//在相应的坐标画出来
}
QSize gradient_test::sizeHint()const
{
return QSize(height(),height());
}
void gradient_test::resizeEvent(QResizeEvent*event)
{
newSize=QImage(event->size(),QImage::Format_ARGB32_Premultiplied);
newSize.fill(palette().background().color());
drawLine(event->size());
update();
}
/*void gradient_test::paintEvent(QPaintEvent*event)
{
QPainter painter(this);
QStyleOption opt;
opt.init(this);
painter.drawImage(0,0,newSize);
style()->drawPrimitive(QStyle::PE_Widget,&opt,&painter,this);
}*/
void gradient_test::paintEvent(QPaintEvent *)
{
QStyleOptionButton option;
option.initFrom(this);
option.state = isDown() ? QStyle::State_Sunken : QStyle::State_Raised;
if (isDefault())
option.features |= QStyleOptionButton::DefaultButton;
option.text = text();
option.icon = icon();
QPainter painter(this);
style()->drawControl(QStyle::CE_PushButton, &option, &painter, this);
}
/*---------------main-----------------*/
#include "widget.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
gradient_test w;
w.show();
return a.exec();
}