Qt下加载图片，在图片上绘制多边形，移动鼠标拉伸多边形

最新推荐文章于 2024-07-17 08:00:00 发布

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#Qt #绘图 #图片 #多边形拉伸 #鼠标拖动

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本文介绍如何在Qt环境下使用QWidget绘制一个可由用户拖动的梯形，并详细解释了相关代码实现。

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本实例是绘制梯形，拖动四个顶点可以拉伸图形

编译环境为 Win7–Qt5.4
1.新建Application工程项目,命名为TiXing,基类选择QWidget;
2.在widget.h的头文件中添加以下声明：

private:
    int j;
    int m_dragging;
    int X[4]={50,200,300,50},Y[4]={100,100,200,200};
protected:
    void mouseReleaseEvent(QMouseEvent*event);
    void mousePressEvent(QMouseEvent*event);
    void mouseMoveEvent(QMouseEvent*event);
    void paintEvent(QPaintEvent *event);

3.然后再widget.cpp文件中添加头文件：

#include <QPainter>
#include <QMouseEvent>
#include <QWidget>
#include <QPen>
#include<QDebug>

继续添加函数定义：

void Widget::paintEvent(QPaintEvent *event)
 {

    QPainter paint(this);
    QImage image;
    image.load("../POLYGON/MyDrawing/luo.jpg");
    qDebug() << image.size() << image.format() <<  image.depth();
    paint.drawImage(QPoint(0, 0), image);
    paint.setPen(QPen(Qt::blue,5));
    for(int i=0;i<4;i++)
      paint.drawPoint(X[i],Y[i]);
    paint.setPen(Qt::red);
    QPolygon pts;
    pts.setPoints(4, X[0],Y[0], X[1],Y[1], X[2],Y[2],X[3],Y[3]);
    paint.drawConvexPolygon(pts);

}
void Widget::mouseReleaseEvent(QMouseEvent *event)
{
        m_dragging = 0;
}
void Widget::mousePressEvent(QMouseEvent *event)
{
  for(int i=0;i<4;i++)
  {
      if(event->pos().x()==X[i]&&event->pos().y()==Y[i])
       {  m_dragging = 1;
          j=i;
          break;
        }
      else continue;
  }
}
void Widget::mouseMoveEvent(QMouseEvent *event)
{
  if (m_dragging==1)
     {
        X[j]=event->pos().x();
        Y[j]=event->pos().y();
        update();
      }
}

4.运行结果如下：
这里写图片描述

附上文件代码：

widget.h
-------------------------------------------------------
#ifndef WIDGET_H
#define WIDGET_H
#include <QWidget>
namespace Ui
{
class Widget;
}

class Widget : public QWidget
{
    Q_OBJECT

public:
    explicit Widget(QWidget *parent = 0);
    ~Widget();

private:
    Ui::Widget *ui;
   // int a;
   // int b;
     int j;
    int m_dragging;
    int X[4]={50,200,300,50},Y[4]={100,100,200,200};
protected:
    void mouseReleaseEvent(QMouseEvent*event);
    void mousePressEvent(QMouseEvent*event);
    void mouseMoveEvent(QMouseEvent*event);
    void paintEvent(QPaintEvent *event);

};

#endif // WIDGET_H

widget.cpp
-------------------------------------------------------
#include "widget.h"
#include "ui_widget.h"
#include <QPainter>
#include <QMouseEvent>
#include <QWidget>
#include <QPen>
#include<QDebug>
Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
    m_dragging = 0;
    ui->setupUi(this);
    resize(500,514);
    setWindowTitle(tr("polygon"));
}

Widget::~Widget()
{
    delete ui;
}
void Widget::paintEvent(QPaintEvent *event)
 {
    QPainter paint(this);
    QImage image;
    image.load("../POLYGON/MyDrawing/luo.jpg");
    qDebug() << image.size() << image.format() << image.depth();
    paint.drawImage(QPoint(0, 0), image);
    paint.setPen(QPen(Qt::blue,5));
    for(int i=0;i<4;i++)
      paint.drawPoint(X[i],Y[i]);
    paint.setPen(Qt::red);
    QPolygon pts;
    pts.setPoints(4, X[0],Y[0], X[1],Y[1], X[2],Y[2],X[3],Y[3]);
    paint.drawConvexPolygon(pts);
}
void Widget::mouseReleaseEvent(QMouseEvent *event)
{
        m_dragging = 0;
}
void Widget::mousePressEvent(QMouseEvent *event)
{
  for(int i=0;i<4;i++)
  {
      if(event->pos().x()==X[i]&&event->pos().y()==Y[i])
       {  m_dragging = 1;
          j=i;
          break;
        }
      //else continue;
  }
}
void Widget::mouseMoveEvent(QMouseEvent *event)
{
  if (m_dragging==1)
     {
        X[j]=event->pos().x();
        Y[j]=event->pos().y();
        update();
      }
}