Qt中视图的缩放对应缩略图中矩形框的缩放

本文实现的目的是：视图缩放时，缩略图中的矩形框也进行缩放，而缩略图中的矩形区域为视图中的可见区。
获取视图中滚动条的值，将其值与缩略图所在的小窗口对比，可通过绘图求其比例，再按比例缩小。
首先提供主要的代码：

connect(view->verticalScrollBar(),&QScrollBar::valueChanged,this,&chunzhongForm::slot_VvalueChanged);
connect(view->horizontalScrollBar(),&QScrollBar::valueChanged,this,&chunzhongForm::slot_HvalueChanged);void chunzhongForm::slot_VvalueChanged(int value)
{if(value != 0 && dlg != NULL){m_y = value;if(dlg->isVisible()){emit signalSetDrawRectSize();}}
}void chunzhongForm::slot_HvalueChanged(int value)
{if(value != 0 && dlg != NULL){m_x = value;if(dlg->isVisible()){emit signalSetDrawRectSize();}}
}connect(this,&chunzhongForm::signalSetDrawRectSize,this,&chunzhongForm::slot_setViewRect);QSize GraphicsView::viewportSizeHint()
{return viewport()->size();
}void chunzhongForm::slot_setViewRect()
{m_viewSize = view->viewportSizeHint();//获取视口大小int x = m_x / (m_viewSize.width() * m_scale)* SMALL_W;int y = m_y / (m_viewSize.height() * m_scale)* SMALL_H;int wid = SMALL_W / m_scale;int hei = SMALL_H / m_scale;outPut<<"小矩形坐标及大小："<<"("<<m_x<<" ,"<<m_y<<" ,"<<wid<<" ,"<<hei<<")";//换成qDebug（）输出QRect rect(x,y,wid,hei);emit signalDrawRect(rect);
}
connect(this,&chunzhongForm::signalDrawRect,dlg,&BreviaryDlg::slot_setRectSize);//缩略图窗口类BreviaryDlg
void BreviaryDlg::slot_setRectSize(QRect &rect)
{m_rect = rect;scene->onSetPreviewRect(rect);
}//缩略图中的自定义场景
void MyGraphicsScene::onSetPreviewRect(QRect rect)
{m_rectSaved = rect;// 内缩几个像素，用矩形外边框来标示viewport显示区域m_pRectItem->setRect(rect.x() - 2/*+ 5*/, rect.y() - 2/*+ 5*/, rect.width() - 4, rect.height() - 4);//设置图形项矩形
}

下面贴出自定义场景类
MyGraphicsScene.h

#pragma once//#include <vld.h>
#include <QGraphicsScene>class MyGraphicsScene : public QGraphicsScene
{Q_OBJECTpublic:MyGraphicsScene(QObject *parent = nullptr);virtual void mouseMoveEvent(QGraphicsSceneMouseEvent *mouseEvent);virtual void mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent);virtual void mouseReleaseEvent(QGraphicsSceneMouseEvent *mouseEvent);Q_SIGNALS:void previewRectMoved(QRect rect);public Q_SLOTS:void onSetPreviewRect(QRect rect);private:QGraphicsRectItem* m_pRectItem;QRect m_rectSaved;bool m_bRectClicked;QPoint m_ptRectRelated;     // 鼠标点击时，相对于红色矩形框的位置
};

MyGraphicsScene.cpp

#include "MyGraphicsScene.h"
#include <QGraphicsSceneMouseEvent>
#include <QGraphicsRectItem>
#include <QDebug>MyGraphicsScene::MyGraphicsScene(QObject *parent): QGraphicsScene(parent), m_bRectClicked(false)
{m_pRectItem = new QGraphicsRectItem(0, 0, 0, 0);QPen penRectItem = QPen(QColor(255, 0, 0));penRectItem.setWidth(2);m_pRectItem->setPen(penRectItem);m_pRectItem->setZValue(1);addItem(m_pRectItem);
}void MyGraphicsScene::onSetPreviewRect(QRect rect)
{m_rectSaved = rect;// 内缩几个像素，用矩形外边框来标示viewport显示区域m_pRectItem->setRect(rect.x() - 2/*+ 5*/, rect.y() - 2/*+ 5*/, rect.width() - 4, rect.height() - 4);
}void MyGraphicsScene::mouseMoveEvent(QGraphicsSceneMouseEvent *mouseEvent)
{QGraphicsScene::mouseMoveEvent(mouseEvent);if (m_bRectClicked) {QPoint ptTopLeft = mouseEvent->scenePos().toPoint() - m_ptRectRelated;m_rectSaved.setTopLeft(ptTopLeft);
//        qDebug()<<"mouseMoveEvent";emit previewRectMoved(m_rectSaved);}
}void MyGraphicsScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{QGraphicsScene::mousePressEvent(mouseEvent);if (m_rectSaved.contains(mouseEvent->scenePos().x(), mouseEvent->scenePos().y())) {m_bRectClicked = true;m_ptRectRelated = mouseEvent->scenePos().toPoint() - m_rectSaved.topLeft();}
}void MyGraphicsScene::mouseReleaseEvent(QGraphicsSceneMouseEvent *mouseEvent)
{QGraphicsScene::mouseReleaseEvent(mouseEvent);m_bRectClicked = false;
}