Qt：QtPainter的坐标系统转换

红太狼 2022-10-24 11:45 174阅读 0赞

/\*  
\* 1、新建QT GUI， 基类选择QWidget，取消“创建界面”  
\* 2、添加资源文件qtlogn：在项目之下添加一个“resources”文件，里面存放"qtblog.png"，然后  
\* 文件-->新建文件/项目--->Qt---> Qt Resource File  
\* 3、在widget.h中添加\#include <QPainter>和重写绘画事件定义：  
\* protected:  
void paintEvent(QPaintEvent \*event);  
\* 4、在widget.cpp中编写重绘事件  
\*/

1、坐标原点移动：

void Widget::paintEvent(QPaintEvent *event)
    {
        QImage image("F:\\MyCode\\qtblog.png");
    
        QPainter painter(this);  //this表示激活画笔
        painter.setPen(QPen(Qt::blue, 1, Qt::DashLine));
        painter.drawRect(0, 0, 100, 100);
    
        QTransform transform;
        transform.translate(50, 50);  //将坐标从当前坐标原点沿着x轴前进50，沿着y轴前进50
    
        painter.setTransform(transform);
        painter.drawImage(0, 0, image);
        painter.end();
    }

![ed4b5db07f567715f65b5f7f30fe467a913.jpg][]

2、坐标系统旋转rotate

void Widget::paintEvent(QPaintEvent *event)
    {
        QImage image("F:\\MyCode\\qtblog.png");
    
        QPainter painter(this);  //this表示激活画笔
        painter.setPen(QPen(Qt::blue, 1, Qt::DashLine));
        painter.drawRect(0, 0, 100, 100);
    
        QTransform transform;
        transform.translate(50, 50);  //坐标沿着x轴前进50，沿着y轴前进50
        transform.rotate(45);  //默认坐标沿着z轴旋转
       //  transform.rotate(70); 
        transform.rotate(45,Qt::ZAxis);
        painter.setTransform(transform);
        painter.drawImage(0, 0, image);
        painter.end();
    }

![cf62ac838ef458fd87fef714e2e6ec613f2.jpg][]

void Widget::paintEvent(QPaintEvent *event)
    {
        QImage image("F:\\MyCode\\qtblog.png");
    
        QPainter painter(this);  //this表示激活画笔
        painter.setPen(QPen(Qt::blue, 1, Qt::DashLine));
        painter.drawRect(0, 0, 100, 100);
    
        QTransform transform;
        transform.translate(50, 50);  //坐标沿着x轴前进50，沿着y轴前进50
        transform.rotate(70,Qt::YAxis);
        painter.setTransform(transform);
        painter.drawImage(0, 0, image);
        painter.end();
    }

![254e011e96667137eb6ce0e5382428f69f8.jpg][]

void Widget::paintEvent(QPaintEvent *event)
    {
        QImage image("F:\\MyCode\\qtblog.png");
    
        QPainter painter(this);  //this表示激活画笔
        painter.setPen(QPen(Qt::blue, 1, Qt::DashLine));
        painter.drawRect(0, 0, 100, 100);
    
        QTransform transform;
        transform.translate(50, 50);  //坐标沿着x轴前进50，沿着y轴前进50
        transform.rotate(80,Qt::XAxis);
        painter.setTransform(transform);  //设置当前旋转坐标为画笔坐标
        painter.drawImage(0, 0, image);
        painter.end();
    }

![4b231c514f58c0d9af654f74c26b1b46043.jpg][]

3、坐标缩放：从而实现图形缩放

void Widget::paintEvent(QPaintEvent *event)
    {
        QImage image("F:\\MyCode\\qtblog.png");
    
        QPainter painter(this);  //this表示激活画笔
        painter.setPen(QPen(Qt::blue, 1, Qt::DashLine));
        painter.drawRect(0, 0, 100, 100);
    
        QTransform transform;
        transform.translate(50, 50);
        transform.rotate(45);
        transform.scale(0.5, 0.5);  //横向和纵向的缩放比例，大于1放大，小于1缩小
    
        painter.setTransform(transform);
        painter.drawImage(0, 0, image);
        painter.end();
    }

![9e21e3067e1958b9230b44bfd00995a751b.jpg][]

资源

![6d95bc8459e6624835e8767e5ee3b2e4.png][]

[ed4b5db07f567715f65b5f7f30fe467a913.jpg]: /images/20221024/558f2db21519449996dffd491972f969.png
[cf62ac838ef458fd87fef714e2e6ec613f2.jpg]: /images/20221024/1fca8213218f415e91763873842b9261.png
[254e011e96667137eb6ce0e5382428f69f8.jpg]: /images/20221024/9a614d28425d49b1b48f200e0036a0da.png
[4b231c514f58c0d9af654f74c26b1b46043.jpg]: /images/20221024/7ea4e10255ce42098993f6218268f80e.png
[9e21e3067e1958b9230b44bfd00995a751b.jpg]: /images/20221024/456febe2aa90435d88e34795b57d8513.png
[6d95bc8459e6624835e8767e5ee3b2e4.png]: /images/20221024/05bc02b5444e40c29dcd67aa85d3aef3.png