QT-QGraphicsView實現圖片放大、縮小、滑鼠拖動、以滑鼠點放大縮小
阿新 • • 發佈：2022-05-30
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https://download.csdn.net/download/zhujianqiangqq/85502024 CSDN程式碼包下載
.pro
1 QT += core gui 2 3 greaterThan(QT_MAJOR_VERSION, 4): QT += widgets 4 5 CONFIG += c++11 6 7 # The following define makes your compiler emit warnings if you use 8 # any Qt feature that has been marked deprecated (the exact warningsView Code9 # depend on your compiler). Please consult the documentation of the 10 # deprecated API in order to know how to port your code away from it. 11 DEFINES += QT_DEPRECATED_WARNINGS 12 13 # You can also make your code fail to compile if it uses deprecated APIs. 14 # In order to do so, uncomment the following line.15 # You can also select to disable deprecated APIs only up to a certain version of Qt. 16 #DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000 # disables all the APIs deprecated before Qt 6.0.0 17 18 SOURCES += \ 19 ImageWidget.cpp \ 20 main.cpp \ 21 mainwindow.cpp 22 23 HEADERS += \ 24 ImageWidget.h \25 mainwindow.h 26 27 FORMS += \ 28 mainwindow.ui 29 30 # Default rules for deployment. 31 qnx: target.path = /tmp/$${TARGET}/bin 32 else: unix:!android: target.path = /opt/$${TARGET}/bin 33 !isEmpty(target.path): INSTALLS += target 34 35 RESOURCES += \ 36 QtQGraphicsView.qrc
main.cpp
1 #include "mainwindow.h" 2 3 #include <QApplication> 4 5 int main(int argc, char *argv[]) 6 { 7 QApplication a(argc, argv); 8 MainWindow w; 9 w.show(); 10 return a.exec(); 11 }View Code
mainwindow.h
1 #ifndef MAINWINDOW_H 2 #define MAINWINDOW_H 3 4 #include <QMainWindow> 5 #include <QPixmap> 6 #include <QGraphicsScene> 7 #include <QGraphicsPixmapItem> 8 #include <QWheelEvent> 9 10 #include "ImageWidget.h" 11 12 QT_BEGIN_NAMESPACE 13 namespace Ui { class MainWindow; } 14 QT_END_NAMESPACE 15 16 class MainWindow : public QMainWindow 17 { 18 Q_OBJECT 19 20 public: 21 MainWindow(QWidget *parent = nullptr); 22 ~MainWindow(); 23 24 void recvShowPicSignal(QImage image);//接收並顯示圖片的函式 25 private: 26 Ui::MainWindow *ui; 27 ImageWidget *m_Image; 28 }; 29 #endif // MAINWINDOW_HView Code
mainwindow.cpp
1 #include "mainwindow.h" 2 #include "ui_mainwindow.h" 3 4 MainWindow::MainWindow(QWidget *parent) 5 : QMainWindow(parent) 6 , ui(new Ui::MainWindow) 7 { 8 ui->setupUi(this); 9 10 setWindowTitle(QStringLiteral("QtQGraphicsView實現圖片放大、縮小、滑鼠拖動、以滑鼠點放大縮小")); 11 12 QPixmap *backgroundPixmap = new QPixmap(":/new/prefix1/QtImage.png"); 13 QImage sizedImage = QImage(backgroundPixmap->toImage()); 14 recvShowPicSignal(sizedImage); 15 } 16 17 MainWindow::~MainWindow() 18 { 19 delete ui; 20 } 21 22 void MainWindow::recvShowPicSignal(QImage image) 23 { 24 ui->graphicsView->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff); 25 ui->graphicsView->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff); 26 27 QPixmap ConvertPixmap = QPixmap::fromImage(image);//The QPixmap class is an off-screen image representation that can be used as a paint device 28 QGraphicsScene *qgraphicsScene = new QGraphicsScene;//要用QGraphicsView就必須要有QGraphicsScene搭配著用 29 m_Image = new ImageWidget(&ConvertPixmap);//例項化類ImageWidget的物件m_Image，該類繼承自QGraphicsItem，是自己寫的類 30 int nwith = ui->graphicsView->width();//獲取介面控制元件Graphics View的寬度 31 int nheight = ui->graphicsView->height();//獲取介面控制元件Graphics View的高度 32 m_Image->setQGraphicsViewWH(nwith,nheight);//將介面控制元件Graphics View的width和height傳進類m_Image中 33 qgraphicsScene->addItem(m_Image);//將QGraphicsItem類物件放進QGraphicsScene中 34 ui->graphicsView->setSceneRect(QRectF(-(nwith/2),-(nheight/2),nwith,nheight));//使視窗的大小固定在原始大小，不會隨圖片的放大而放大（預設狀態下圖片放大的時候視窗兩邊會自動出現滾動條，並且視窗內的視野會變大），防止圖片放大後重新縮小的時候視窗太大而不方便觀察圖片 35 ui->graphicsView->setScene(qgraphicsScene);//Sets the current scene to scene. If scene is already being viewed, this function does nothing. 36 ui->graphicsView->setFocus();//將介面的焦點設定到當前Graphics View控制元件 37 }View Code
mainwindow.ui
1 <?xml version="1.0" encoding="UTF-8"?> 2 <ui version="4.0"> 3 <class>MainWindow</class> 4 <widget class="QMainWindow" name="MainWindow"> 5 <property name="geometry"> 6 <rect> 7 <x>0</x> 8 <y>0</y> 9 <width>600</width> 10 <height>400</height> 11 </rect> 12 </property> 13 <property name="windowTitle"> 14 <string>MainWindow</string> 15 </property> 16 <widget class="QWidget" name="centralwidget"> 17 <widget class="QGraphicsView" name="graphicsView"> 18 <property name="geometry"> 19 <rect> 20 <x>0</x> 21 <y>0</y> 22 <width>600</width> 23 <height>400</height> 24 </rect> 25 </property> 26 </widget> 27 </widget> 28 </widget> 29 <resources/> 30 <connections/> 31 </ui>View Code
ImageWidget.h
1 #ifndef IMAGEWIDGET_H 2 #define IMAGEWIDGET_H 3 4 #include <QWidget> 5 #include <QtGui> 6 #include <QPixmap> 7 #include <QPainter> 8 #include <QRectF> 9 #include <QMouseEvent> 10 #include <QPointF> 11 #include <QDragEnterEvent> 12 #include <QGraphicsSceneWheelEvent> 13 #include <QGraphicsItem> 14 15 enum Enum_ZoomState{ 16 NO_STATE, 17 RESET, 18 ZOOM_IN, 19 ZOOM_OUT 20 }; 21 // class ImageWidget :public QObject, QGraphicsItem 22 class ImageWidget :public QGraphicsItem 23 { 24 //Q_OBJECT 25 public: 26 ImageWidget(QPixmap *pixmap); 27 QRectF boundingRect() const; 28 void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget); 29 void wheelEvent(QGraphicsSceneWheelEvent *event); 30 void ResetItemPos(); 31 void mousePressEvent(QGraphicsSceneMouseEvent *event); 32 void mouseMoveEvent(QGraphicsSceneMouseEvent *event); 33 void mouseReleaseEvent(QGraphicsSceneMouseEvent *event); 34 qreal getScaleValue() const; 35 void setQGraphicsViewWH(int nwidth,int nheight); 36 private: 37 qreal m_scaleValue; 38 qreal m_scaleDafault; 39 QPixmap m_pix; 40 int m_zoomState; 41 bool m_isMove; 42 QPointF m_startPos; 43 }; 44 #endif // IMAGEWIDGET_HView Code
ImageWidget.cpp
1 #include "ImageWidget.h" 2 3 #include <QDebug> 4 #include <QGraphicsSceneMouseEvent> 5 #include <QPointF> 6 #include <QGraphicsSceneDragDropEvent> 7 #include <QDrag> 8 #include <math.h> 9 10 ImageWidget::ImageWidget(QPixmap *pixmap) 11 { 12 m_pix = *pixmap; 13 setAcceptDrops(true);//If enabled is true, this item will accept hover events; otherwise, it will ignore them. By default, items do not accept hover events. 14 m_scaleValue = 0; 15 m_scaleDafault = 0; 16 m_isMove = false; 17 } 18 19 QRectF ImageWidget::boundingRect() const 20 { 21 return QRectF(-m_pix.width() / 2, -m_pix.height() / 2, 22 m_pix.width(), m_pix.height()); 23 } 24 25 void ImageWidget::paint(QPainter *painter, const QStyleOptionGraphicsItem *, 26 QWidget *) 27 { 28 painter->drawPixmap(-m_pix.width() / 2, -m_pix.height() / 2, m_pix); 29 } 30 31 void ImageWidget::mousePressEvent(QGraphicsSceneMouseEvent *event) 32 { 33 if(event->button()== Qt::LeftButton) 34 { 35 m_startPos = event->pos();//滑鼠左擊時，獲取當前滑鼠在圖片中的座標， 36 m_isMove = true;//標記滑鼠左鍵被按下 37 } 38 else if(event->button() == Qt::RightButton) 39 { 40 ResetItemPos();//右擊滑鼠重置大小 41 } 42 43 } 44 45 void ImageWidget::mouseMoveEvent(QGraphicsSceneMouseEvent *event) 46 { 47 if(m_isMove) 48 { 49 QPointF point = (event->pos() - m_startPos)*m_scaleValue; 50 moveBy(point.x(), point.y()); 51 } 52 } 53 54 void ImageWidget::mouseReleaseEvent(QGraphicsSceneMouseEvent *) 55 { 56 m_isMove = false;//標記滑鼠左鍵已經抬起 57 } 58 59 60 void ImageWidget::wheelEvent(QGraphicsSceneWheelEvent *event)//滑鼠滾輪事件 61 { 62 if((event->delta() > 0)&&(m_scaleValue >= 50))//最大放大到原始影象的50倍 63 { 64 return; 65 } 66 else if((event->delta() < 0)&&(m_scaleValue <= m_scaleDafault))//影象縮小到自適應大小之後就不繼續縮小 67 { 68 ResetItemPos();//重置圖片大小和位置，使之自適應控制元件視窗大小 69 } 70 else 71 { 72 qreal qrealOriginScale = m_scaleValue; 73 if(event->delta() > 0)//滑鼠滾輪向前滾動 74 { 75 m_scaleValue*=1.1;//每次放大10% 76 } 77 else 78 { 79 m_scaleValue*=0.9;//每次縮小10% 80 } 81 setScale(m_scaleValue); 82 if(event->delta() > 0) 83 { 84 moveBy(-event->pos().x()*qrealOriginScale*0.1, -event->pos().y()*qrealOriginScale*0.1);//使圖片縮放的效果看起來像是以滑鼠所在點為中心進行縮放的 85 } 86 else 87 { 88 moveBy(event->pos().x()*qrealOriginScale*0.1, event->pos().y()*qrealOriginScale*0.1);//使圖片縮放的效果看起來像是以滑鼠所在點為中心進行縮放的 89 } 90 } 91 } 92 93 void ImageWidget::setQGraphicsViewWH(int nwidth, int nheight)//將主介面的控制元件QGraphicsView的width和height傳進本類中，並根據影象的長寬和控制元件的長寬的比例來使圖片縮放到適合控制元件的大小 94 { 95 int nImgWidth = m_pix.width(); 96 int nImgHeight = m_pix.height(); 97 qreal temp1 = nwidth*1.0/nImgWidth; 98 qreal temp2 = nheight*1.0/nImgHeight; 99 if(temp1>temp2) 100 { 101 m_scaleDafault = temp2; 102 } 103 else 104 { 105 m_scaleDafault = temp1; 106 } 107 setScale(m_scaleDafault); 108 m_scaleValue = m_scaleDafault; 109 } 110 111 void ImageWidget::ResetItemPos()//重置圖片位置 112 { 113 m_scaleValue = m_scaleDafault;//縮放比例回到一開始的自適應比例 114 setScale(m_scaleDafault);//縮放到一開始的自適應大小 115 setPos(0,0); 116 } 117 118 qreal ImageWidget::getScaleValue() const 119 { 120 return m_scaleValue; 121 }View Code
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