31 绘图设备

常用绘图设备：

• QWidget
• QPixmap
• QBitmap
• QImage
• QPicture

 代码：

//widget.h
#ifndef WIDGET_H
#define WIDGET_H

#include 

namespace Ui {
class Widget;
}

class Widget : public QWidget
{
    Q_OBJECT

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

    //利用Image访问像素点
    void paintEvent(QPaintEvent *);

private:
    Ui::Widget *ui;
};

#endif // WIDGET_H

//widget.cpp
#include "widget.h"
#include "ui_widget.h"
#include "QPainter"
#include "QPicture"

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

    //QPixmap做绘图设备，对不同平台做了显示优化
    QPixmap pix(300,300);
    pix.fill(Qt::white);
    QPainter painter(&pix);
    painter.setPen(QPen(Qt::green));
    painter.drawEllipse(QPoint(150,150),100,100);
    pix.save("D:\\QT\\QtProjects\\14_QPaintDevice\\pix.png");

    //QImage做绘图设备，专门为像素级访问做优化
    QImage img(300,300,QImage::Format_RGB32);
    img.fill(Qt::white);
    QPainter painter(&img);
    painter.setPen(QPen(Qt::green));
    painter.drawEllipse(QPoint(150,150),100,100);
    img.save("D:\\QT\\QtProjects\\14_QPaintDevice\\img.png");

    //QPicture做绘图设备  记录和重现画家的绘图指令
    QPicture pic;
    QPainter painter;
    painter.begin(&pic);

    painter.setPen(QPen(Qt::red));
    painter.drawEllipse(QPoint(150,150),100,100);

    painter.end();
    pic.save("D:\\QT\\QtProjects\\14_QPaintDevice\\pic.zt");//后缀名自定义，不影响

}

void Widget::paintEvent(QPaintEvent *){
    QPainter painter(this);
    QImage img;
    img.load(":/imgs/Luffy.png");
    for(int i=50;i<100;i++){
        for(int j=50;j<100;j++){
            QRgb val = img.pixel(j,i);
            img.setPixel(i,j,val);
        }
    }
    painter.drawImage(0,0,img);

    //重现QPicture的绘图
    QPainter painter(this);
    QPicture pic;
    pic.load("D:\\QT\\QtProjects\\14_QPaintDevice\\pic.zt");
    painter.drawPicture(0,0,pic);

}

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