Qt-QPainter实现图片的绘图、平移、缩放、旋转、扭曲

 

相关资料：

https://download.csdn.net/download/zhujianqiangqq/85500981     csdn代码包下载

 

.pro

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

CONFIG += c++11

# The following define makes your compiler emit warnings if you use
# any Qt feature that has been marked deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \
    main.cpp \
    mainwindow.cpp

HEADERS += \
    mainwindow.h

FORMS += \
    mainwindow.ui

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

RESOURCES += \
    QtQPixmap.qrc

main.cpp

#include "mainwindow.h"

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

 mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QPainter>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
    void paintEvent(QPaintEvent *);

private:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

 mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

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

    setWindowTitle(QStringLiteral("QPainter实现图片的绘图、平移、缩放、旋转、扭曲"));
}

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

void MainWindow::paintEvent(QPaintEvent *)
{
    // 绘图
    QPainter painter(this);
    QPixmap pix;
    pix.load(":/new/prefix1/abc.png");
    painter.drawPixmap(0,0,100,100,pix);

    // 利用更改坐标原点实现平移
    painter.translate(100,100); //将（100，100）设为坐标原点
    painter.drawPixmap(0,0,100,100,pix);
    painter.translate(-100, -100); //让图片的中心作为旋转的中心

    // 实现图片的缩放
    painter.translate(100,100); //将（100，100）设为坐标原点
    qreal width = pix.width(); //获得以前图片的宽和高
    qreal height = pix.height();

    pix = pix.scaled(width*2,height*2,Qt::KeepAspectRatio);
    //将图片的宽和高都扩大两倍，并且在给定的矩形内保持宽高的比值
    painter.drawPixmap(100,100,pix);
    painter.translate(-100, -100); //让图片的中心作为旋转的中心

    // 实现图片的旋转
    painter.translate(500, 400); //让图片的中心作为旋转的中心
    painter.rotate(90); //顺时针旋转90度
    painter.drawPixmap(0,0,100,100,pix);
    painter.rotate(-90); //顺时针旋转90度
    painter.translate(-500, -400); //让图片的中心作为旋转的中心

    // 实现图片的扭曲
    painter.translate(500, 500); //让图片的中心作为旋转的中心
    painter.shear(0.5,0); //横向扭曲
    painter.drawPixmap(0,0,100,100,pix);
    painter.translate(-500, -500); //让图片的中心作为旋转的中心
}

 mainwindow.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>600</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget"/>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>800</width>
     <height>22</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>

 

 

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