Qt 绘图(QBitmap,QPixmap,QImage,QPicture)

• QPainter绘图绘图设备（QPixmap，QImage，QBitmap，QPicture）
  • 重写绘图事件，虚函数
  • 如果窗口绘图，必须放在绘图事件里实现
  • 绘图事件内部自动调用，窗口需要重绘的时候，状态改变
• QPixmap图片背景透明，针对屏幕进行优化了，和平台相关，不能对图片进行修改
• QImage 和平台无关，可以对图片进行修改，在线程中绘图
• QPicture 保存绘图 的状态（二进制文件）
• pixmap.save("../pixmap.png"); 保存图片
• setWindowFlags(Qt::FramelessWindowHint | windowFlags());去除边框
• setAttribute(Qt::WA_TranslucentBackground);设置透明

QPainter

 #ifndef WIDGET_H
 #define WIDGET_H

 #include <QWidget>

 namespace Ui {
 class Widget;
 }

 class Widget : public QWidget
 {
     Q_OBJECT

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

 protected:
     void paintEvent(QPaintEvent *event);

 private slots:
     void on_pushButton_clicked();

 private:
     Ui::Widget *ui;
     int x=;
 };

 #endif // WIDGET_H

 #include "widget.h"
 #include "ui_widget.h"
 #include <QPainter>
 #include <QPen>
 #include <QBrush>
 Widget::Widget(QWidget *parent) :
     QWidget(parent),
     ui(new Ui::Widget)
 {
     ui->setupUi(this);
 }

 Widget::~Widget()
 {
     delete ui;
 }

 void Widget::paintEvent(QPaintEvent *event)
 {
     //QPainter p(this);
     QPainter p;//创建画家对象
     p.begin(this);//指定当前窗口为绘图设备
     //画背景图
     //p.drawPixmap(0,0, width(), height(), QPixmap("../Image/bk.png"));
     //p.drawPixmap(rect(),QPixmap("../Image/bk.png"));

     //定义画笔
     QPen pen;
     pen.setWidth();//设置线宽
     pen.setColor(QColor(,,));//rgb
     pen.setStyle(Qt::DashDotDotLine);

     QBrush brush;
     brush.setColor(Qt::red);
     brush.setStyle(Qt::Dense1Pattern);

     //p.setPen(pen);
     p.setBrush(brush);
     //画直线
     p.drawLine(,,,);
     p.drawLine(, ,, );

     //画矩形
     p.drawRect(x,,,);

     p.drawEllipse(QPoint(,),,);

     p.drawPixmap(x,,,,QPixmap("../Image/face.png"));

     p.end();
 }

 void Widget::on_pushButton_clicked()
 {
     x += ;
     if(x>width())
     {
         x = ;
     }
     update();
 }

QBitmap

 #ifndef WIDGET_H
 #define WIDGET_H

 #include <QWidget>

 namespace Ui {
 class Widget;
 }

 class Widget : public QWidget
 {
     Q_OBJECT

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

 protected:
     void paintEvent(QPaintEvent *event);

 private:
     Ui::Widget *ui;
 };

 #endif // WIDGET_H

 #include "widget.h"
 #include "ui_widget.h"
 #include <QPainter>
 #include <QBitmap>
 Widget::Widget(QWidget *parent) :
     QWidget(parent),
     ui(new Ui::Widget)
 {
     ui->setupUi(this);
 }

 Widget::~Widget()
 {
     delete ui;
 }

 void Widget::paintEvent(QPaintEvent *event)
 {
     QPainter p(this);
     //QPixmap图片背景透明
     p.drawPixmap(,,QPixmap("../Image/butterfly.png"));
     //QBitmap
     p.drawPixmap(,, QBitmap("../Image/butterfly.png"));
     //QPixmap 图片背景白色
     QPixmap pixmap;
     pixmap.load("../Image/butterfly1.png");
 }

QPixmap

 #ifndef WIDGET_H
 #define WIDGET_H

 #include <QWidget>

 namespace Ui {
 class Widget;
 }

 class Widget : public QWidget
 {
     Q_OBJECT

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

 private:
     Ui::Widget *ui;
 };

 #endif // WIDGET_H

 #include "widget.h"
 #include "ui_widget.h"
 #include <QPainter>
 Widget::Widget(QWidget *parent) :
     QWidget(parent),
     ui(new Ui::Widget)
 {
     ui->setupUi(this);
     QPixmap pixmap(, );
     QPainter p(&pixmap);
     p.fillRect(,,,,QBrush(Qt::white));

     pixmap.fill(Qt::white);
     p.drawPixmap(,,,,QPixmap("../Image/face.png"));

     //保存图片
     pixmap.save("../pixmap.png");
 }

 Widget::~Widget()
 {
     delete ui;
 }

QImage

 #include "widget.h"
 #include "ui_widget.h"
 #include <QPainter>

 Widget::Widget(QWidget *parent) :
     QWidget(parent),
     ui(new Ui::Widget)
 {
     ui->setupUi(this);

     QImage image(,,QImage::Format_ARGB32);
     QPainter p;
     p.begin(&image);

     p.drawLine(,,,);

     for(int i=;i<;i++)
     {
         for(int j=;j<;j++)
         {
             image.setPixel(QPoint(i,j),qRgb(,,));

         }
     }
     p.end();

     image.save("../image.png");
 }

 Widget::~Widget()
 {
     delete ui;
 }

QPicture

 #include "widget.h"
 #include "ui_widget.h"
 #include <QPainter>
 #include <QPicture>
 Widget::Widget(QWidget *parent) :
     QWidget(parent),
     ui(new Ui::Widget)
 {
     ui->setupUi(this);
     QPicture picture;
     QPainter p;
     p.begin(&picture);
     p.drawLine(,,,);
     p.end();

     picture.save("../picture.png");
 }

 Widget::~Widget()
 {
     delete ui;
 }

 void Widget::paintEvent(QPaintEvent *event)
 {
 //    QPicture pic;
 //    pic.load("../picture.png");
     QPainter p(this);
 //    p.drawPicture(0,0,pic);

     QPixmap pixmap;
     pixmap.load("../Image/face.png");
     QImage tempImage = pixmap.toImage();
     p.drawImage(,, tempImage);

     QImage image;
     image.load("../Image/face.png");
     QPixmap tempPixmap = QPixmap::fromImage(image);
 }　　

窗口透明

 #include "widget.h"
 #include "ui_widget.h"
 #include <QPainter>
 #include <QMouseEvent>
 #include <QDebug>
 Widget::Widget(QWidget *parent) :
     QWidget(parent),
     ui(new Ui::Widget)
 {
     ui->setupUi(this);
     setWindowFlags(Qt::FramelessWindowHint | windowFlags());

     setAttribute(Qt::WA_TranslucentBackground);
 }

 Widget::~Widget()
 {
     delete ui;
 }

 void Widget::paintEvent(QPaintEvent *event)
 {
     QPainter p(this);
     p.drawLine(,,,);
 }

 void Widget::mousePressEvent(QMouseEvent *event)
 {
     if(event->button() == Qt::RightButton)
     {
      close();
      qDebug()<<"close";
     }
     else if(event->button() == Qt::LeftButton)
     {
         p = event->globalPos() - this->frameGeometry().topLeft();
         qDebug()<<"left";
     }
 }

 void Widget::mouseMoveEvent(QMouseEvent *event)
 {
     if(event->button() & Qt::LeftButton)
     {
             move(event->globalPos()-p);
     }
 }