qt5之QImage,QBitmap,QPixmap

绘图（打开jpg,bmp文件显示）

1，QBitmap和QPixmap的使用

widgt.cpp

#include "widget.h"
#include "ui_widget.h"
#include 
#include 

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

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

void Widget::paintEvent(QPaintEvent *)
{
    QPainter p(this);
    //QPixmap 图片背景透明
    p.drawPixmap(0, 0, QPixmap("../Image/butterfly.png"));
    //QBitmap 图片背景透明
    p.drawPixmap(200, 0, QBitmap("../Image/butterfly.png"));

     //QPixmap 图片背景白色
    QPixmap pixmap;
    pixmap.load("../Image/butterfly1.png");
    p.drawPixmap(0, 200, pixmap);

    //QBitmap 图片背景白色
    QBitmap bitmap;
    bitmap.load("../Image/butterfly1.png");
    p.drawPixmap(200, 200, bitmap);

}

widgt.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();

protected:
    //重写绘图事件
    //如果给窗口绘图，一定要在paintEvent()绘图
    void paintEvent(QPaintEvent *);

private:
    Ui::Widget *ui;
};

#endif // WIDGET_H

2，背景填充：

#include "widget.h"
#include "ui_widget.h"
#include 

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

    //绘图设备， 400*300
    QPixmap pixmap(400, 300);

    QPainter p(&pixmap);
    //填充白色背景色
    //p.fillRect(0, 0, 400, 300, QBrush(Qt::white));

    pixmap.fill(Qt::white);

    p.drawPixmap(0, 0, 80, 80, QPixmap("../Image/face.png"));

    //保存图片
    pixmap.save("../pixmap.jpg");



}

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

3，setpixel 函数功能：该函数将指定坐标处的像素设为指定的颜色。

#include "widget.h"
#include "ui_widget.h"
#include 

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

    //创建一个绘图设备，QImage::Format_ARGB32背景是透明
    QImage image(400, 300, QImage::Format_ARGB32);
    QPainter p;
    p.begin(&image);

    //绘图
    p.drawImage(0, 0, QImage("../Image/face.png"));

    //对绘图设备前50个像素点进行操作
    for(int i = 0; i < 50; i++)
    {
        for(int j = 0; j < 50; j++)
        {
            image.setPixel(QPoint(i, j), qRgb(0, 255, 0));
            //image.pixel(QPoint(i, j));
        }
    }

    p.end();

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

}

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

4,QPicture的使用：

#include "widget.h"
#include "ui_widget.h"
#include 
#include 
#include 
#include 

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

    QPicture picture;
    QPainter p;
    p.begin(&picture);

    p.drawPixmap(0, 0, 80, 80, QPixmap("../Image/face.png"));
    p.drawLine(50, 50, 150, 50);

    p.end();

    //保存的是二进制文件
    picture.save("../picture.png");
}

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

void Widget::paintEvent(QPaintEvent *)
{

#if 0
    QPicture pic;
    pic.load("../picture.png"); //加载文件

    QPainter p(this);
    p.drawPicture(0, 0, pic);

#endif

    QPainter p(this);
    QPixmap pixmap;
    pixmap.load("../Image/face.png");

    //QPixmap -> QImage
    QImage tempImage = pixmap.toImage();
    p.drawImage(0, 0, tempImage);


    QImage image;
    image.load("../Image/face.png");

    //QImage -> QPixmap
    QPixmap tempPixmap = QPixmap::fromImage(image);
    p.drawPixmap(100, 0, tempPixmap);

}