<pre name="code" class="cpp">
<pre style="margin-top: 0px; margin-bottom: 0px;"><span style=" color:#000080;">#ifndef</span><span style=" color:#c0c0c0;"> </span>DIALOG_H
#define DIALOG_H
#include <QDialog>
#include <QMouseEvent>
#include <QPushButton>
namespace Ui {
class Dialog;
}
class Dialog : public QDialog
{
Q_OBJECT
public:
explicit Dialog(QWidget *parent = 0);
~Dialog();
private:
Ui::Dialog *ui;
QPixmap pix;
QPoint lastPoint;
QPoint endPoint;
qreal scale;
QPushButton *button;
QPixmap tempPix; //辅助画布
bool isDrawing; //标志是否正在绘图
protected:
void paintEvent(QPaintEvent *);
void mousePressEvent(QMouseEvent *);
void mouseMoveEvent(QMouseEvent *);
void mouseReleaseEvent(QMouseEvent *);
private slots:
void zoomIn();
};
#endif // DIALOG_H
#include "dialog.h"
#include "ui_dialog.h"
#include <QPainter>
Dialog::Dialog(QWidget *parent) :
QDialog(parent),
ui(new Ui::Dialog)
{
ui->setupUi(this);
resize(600, 500); //窗口大小设置为600*500
pix = QPixmap(200, 200);
pix.fill(Qt::white);
isDrawing = false;
//设置初始放大倍数为1，即不放大
scale =1;
//新建按钮对象
button = new QPushButton(this);
//设置按钮显示文本
button->setText(tr("zoomIn"));
//设置按钮放置位置
button->move(500, 450);
//对按钮的单击事件和其槽函数进行关联
connect(button, SIGNAL(clicked()), this, SLOT(zoomIn()));
}
Dialog::~Dialog()
{
delete ui;
}
void Dialog::paintEvent(QPaintEvent *)
{
#if 0
if(scale!=1) //如果进行放大操作
{
//临时画布，大小变化了scale倍
QPixmap copyPix(pix.size()*scale);
QPainter pter(©Pix);
pter.scale(scale, scale);
//将以前画布上的内容复制到现在的画布上
pter.drawPixmap(0, 0, pix);
//将放大后的内容再复制回原来的画布上
pix = copyPix;
//让scale重新置1
scale =1;
}
QPainter pp(&pix); // 根据鼠标指针前后两个位置就行绘制直线
//pp.drawLine(lastPoint, endPoint); // 让前一个坐标值等于后一个坐标值，这样就能实现画出连续的线
pp.drawLine(lastPoint/scale, endPoint/scale);
lastPoint = endPoint;
QPainter painter(this);
//进行放大操作
painter.scale(scale, scale);
painter.drawPixmap(0, 0, pix);
#endif
int x,y,w,h;
x = lastPoint.x();
y = lastPoint.y();
w = endPoint.x() - x;
h = endPoint.y() - y;
QPainter painter(this);
if(isDrawing) //如果正在绘图，就在辅助画布上绘制
{
//将以前pix中的内容复制到tempPix中，保证以前的内容不消失
tempPix = pix;
QPainter pp(&tempPix);
pp.drawRect(x,y,w,h);
painter.drawPixmap(0, 0, tempPix);
} else {
QPainter pp(&pix);
pp.drawRect(x,y,w,h);
painter.drawPixmap(0,0,pix);
}
}
void Dialog::mousePressEvent(QMouseEvent *event)
{
if(event->button()==Qt::LeftButton) //鼠标左键按下
{
lastPoint = event->pos();
isDrawing = true; //正在绘图
}
}
void Dialog::mouseMoveEvent(QMouseEvent *event)
{
if(event->buttons()&Qt::LeftButton) //鼠标左键按下的同时移动鼠标
{
endPoint = event->pos();
update(); //进行绘制
}
}
void Dialog::mouseReleaseEvent(QMouseEvent *event)
{
if(event->button() == Qt::LeftButton) //鼠标左键释放
{
endPoint = event->pos();
isDrawing = false; //结束绘图
update();
}
}
void Dialog::zoomIn()
{
scale *=2;
update();
}
Qt 涂鸦板 
Qt 涂鸦板 
