实现图元的旋转、缩放、切变和位移

效果：

 

mainwindow.h

#ifndef MAINWIDGET_H
#define MAINWIDGET_H
#include <QWidget>
#include <QGraphicsView>
#include <QGraphicsScene>
#include <QFrame>
#include <QGraphicsView>
#include "pixitem.h"
#include <math.h>
class MainWidget : public QWidget
{
    Q_OBJECT

public:
    MainWidget(QWidget *parent = nullptr);
    ~MainWidget();

public:
    void createControlFrame();

private:
    int angle;
    qreal scaleValue;
    qreal shearValue;
    qreal translateValue;

    QGraphicsScene *scene;
    QGraphicsView *view;
    QFrame *ctrlFrame;
    PixItem  *pixItem;

public slots:
    void slotRotate(int);
    void slotScale(int);
    void slotShear(int);
    void slotTranlate(int);

};
#endif // MAINWIDGET_H

mainwindow.cpp

#include "mainwidget.h"
#include <QSlider>
#include <QHBoxLayout>
#include <QVBoxLayout>
#include <QGroupBox>

MainWidget::MainWidget(QWidget *parent)
    : QWidget(parent)
{
    setWindowTitle(QStringLiteral("Graphics Item Transformation"));
    angle=0;
    scaleValue=5;
    shearValue=5;
    translateValue=50;

    scene=new QGraphicsScene(this);
    scene->setSceneRect(-200,-200,400,400);

    view=new QGraphicsView(this);
    view->setScene(scene);
    view->setMinimumSize(400,400);


    QPixmap *pixmap=new QPixmap(":/new/butffly.png");
    pixItem=new PixItem(pixmap); //新建一个pixitm图元，为它传一个图片用于显示
    scene->addItem(pixItem);
    pixItem->setPos(0,0);

    ctrlFrame=new QFrame(this);
    createControlFrame();  //新建主窗体右侧的面板

    //主窗口布局
    QHBoxLayout *mainLayout=new QHBoxLayout;
    mainLayout->setMargin(10);
    mainLayout->setSpacing(20);
    mainLayout->addWidget(view);
    mainLayout->addWidget(ctrlFrame);
    this->setLayout(mainLayout); //设置布局

}

MainWidget::~MainWidget()
{
}

void MainWidget::createControlFrame()
{
    //旋转控制
    QSlider *rotateSlider=new QSlider;
    rotateSlider->setOrientation(Qt::Horizontal);
    rotateSlider->setRange(0,360);

    QHBoxLayout *rotateLayout= new QHBoxLayout;
    rotateLayout->addWidget(rotateSlider);

    QGroupBox *rotateGroup=new QGroupBox(QStringLiteral("Rotate"));
    rotateGroup->setLayout(rotateLayout);


    //缩放控制
    QSlider *scaleSlider=new QSlider;
    scaleSlider->setOrientation(Qt::Horizontal);
    scaleSlider->setRange(0,2*scaleValue);
    scaleSlider->setValue(scaleValue);

    QHBoxLayout *scaleLayout= new QHBoxLayout;
    scaleLayout->addWidget(scaleSlider);

    QGroupBox *scaleGroup=new QGroupBox(QStringLiteral("Scale"));;
    scaleGroup->setLayout(scaleLayout);


    //切变控制
    QSlider *shearSlider=new QSlider;
    shearSlider->setOrientation(Qt::Horizontal);
    shearSlider->setRange(0,2*shearValue);
    shearSlider->setValue(shearValue);

    QHBoxLayout *shearLayout= new QHBoxLayout;
    shearLayout->addWidget(shearSlider);

    QGroupBox *shearGroup=new QGroupBox(QStringLiteral("Shear"));;
    shearGroup->setLayout(shearLayout);


    //位移控制
    QSlider *translateSlider=new QSlider;
    translateSlider->setOrientation(Qt::Horizontal);
    translateSlider->setRange(0,2*translateValue); //设置Slider的范围
    translateSlider->setValue(translateValue);

    QHBoxLayout *translateLayout= new QHBoxLayout;
    translateLayout->addWidget(translateSlider);

    QGroupBox *translateGroup=new QGroupBox(QStringLiteral("Translate"));;
    translateGroup->setLayout(translateLayout);

    connect(rotateSlider,SIGNAL(valueChanged(int)),this,SLOT(slotRotate(int)));
    connect(scaleSlider,SIGNAL(valueChanged(int)),this,SLOT(slotScale(int)));
    connect(shearSlider,SIGNAL(valueChanged(int)),this,SLOT(slotShear(int)));
    connect(translateSlider,SIGNAL(valueChanged(int)),this,SLOT(slotTranlate(int)));

   //控制面板布局
    QVBoxLayout *frameLayout=new QVBoxLayout;
    frameLayout->setMargin(10);
    frameLayout->setSpacing(20);
    frameLayout->addWidget(rotateGroup);
    frameLayout->addWidget(scaleGroup);
    frameLayout->addWidget(shearGroup);
    frameLayout->addWidget(translateGroup);
    ctrlFrame->setLayout(frameLayout);

}

void MainWidget::slotRotate(int value)
{
   view->rotate(value-angle);
   angle=value;

}

void MainWidget::slotScale(int value)
{
    qreal s;
    if(value>scaleValue)
    {
        s=pow(1.1,value-scaleValue);
    }
    else
    {
        s=pow(1/1.1,scaleValue-value);
    }
    view->scale(s,s);
    scaleValue=value;
}

void MainWidget::slotShear(int value)
{
    view->shear((value-shearValue)/10.0,0);
    shearValue=value;
}

void MainWidget::slotTranlate(int value)
{
    view->translate(value-translateValue,value-translateValue);
    translateValue=value;
}

pixItem.h

#ifndef PIXITEM_H
#define PIXITEM_H
#include <QGraphicsItem>
#include <QPixmap>
#include <QPainter>
class PixItem : public QGraphicsItem
{
public:
    PixItem(QPixmap *pixmap);

    QRectF boundingRect() const ;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = nullptr) ;

private:
    QPixmap pix;  //作为图元显示的图片
};

#endif // PIXITEM_H

pixItem.cpp

#include "pixitem.h"

PixItem::PixItem(QPixmap *pixmap)
{
    pix = *pixmap;
}

QRectF PixItem::boundingRect() const
{
    return QRectF(-2-pix.width()/2,-2-pix.height()/2,pix.width()+4,pix.height()+4);
}

void PixItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    painter->drawPixmap(-pix.width()/2,-pix.height()/2,pix);

    /*inline void QPainter::drawPixmap(int x, int y, const QPixmap &pm)
    {
        drawPixmap(QPointF(x, y), pm);
    }*/
}