Qt 图片缩放，支持滚轮和按键缩放

#include "pixitem.h" #include <QDebug> #include <QGraphicsSceneMouseEvent> #include <QPointF> #include <QGraphicsSceneDragDropEvent> #include <QDrag> #include <math.h> //构造函数初始化了变量pix PixItem::PixItem(QPixmap *pixmap) { pix = *pixmap; setAcceptDrops(true); //设置可拖拽 m_scaleValue = 0; m_isMove = false; } //实现自己的图元边界函数 QRectF PixItem::boundingRect() const { return QRectF(-pix.width() / 2, -pix.height() / 2, pix.width(), pix.height()); } //只需QPainter的drawPixmap()函数将图元图片绘出即可 void PixItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *) { painter->drawPixmap(-pix.width() / 2, -pix.height() / 2, pix); } //鼠标点击事件 局部缩放 void PixItem::mousePressEvent(QGraphicsSceneMouseEvent *event) { m_startPos = event->pos(); m_isMove = true; int scaleValue = m_scaleValue; if(m_zoomState == ZOOM_IN) //局部放大 { scaleValue++; } else if(m_zoomState == ZOOM_OUT) //局部缩小 { scaleValue--; } if (scaleValue > ZOOM_IN_TIMES || scaleValue < ZOOM_OUT_TIMES) return; if (m_scaleValue != scaleValue) { setTransformOriginPoint(event->pos().x(), event->pos().y()); } m_scaleValue = scaleValue; qreal s; //实现局部缩放 if(m_scaleValue > 0) { s = pow(1.1, m_scaleValue); //放大 计算x的y方次 参数都是double类型 }else { s = pow(1 / 1.1, -m_scaleValue); //缩小 } setScale(s); } void PixItem::mouseMoveEvent(QGraphicsSceneMouseEvent *event) { if(m_isMove) { QPointF point = event->pos() - m_startPos; moveBy(point.x(), point.y()); } } void PixItem::mouseReleaseEvent(QGraphicsSceneMouseEvent *) { m_isMove = false; } //使用滚轮整体缩放 void PixItem::wheelEvent(QGraphicsSceneWheelEvent *event) { setZoomState(NO_STATE); int scaleValue = m_scaleValue; if(event->delta() > 0) //delta（）为正，滚轮向上滚 { scaleValue++; } else { scaleValue--; } if (scaleValue > ZOOM_IN_TIMES || scaleValue < ZOOM_OUT_TIMES) return; m_scaleValue = scaleValue; qreal s; if(m_scaleValue > 0) { s = pow(1.1, m_scaleValue); //放大 计算x的y方次 参数都是double类型 } else { s = pow(1 / 1.1, -m_scaleValue); //缩小 } setScale(s); setTransformOriginPoint(event->pos().x(), event->pos().y()); } //从widget获取的缩放值，用于同步滚轮和按键 void PixItem::setScaleValue(const int &scaleValue) { if (scaleValue > ZOOM_IN_TIMES || scaleValue < ZOOM_OUT_TIMES) return; m_scaleValue = scaleValue; qreal s; if(m_scaleValue > 0) { s = pow(1.1, m_scaleValue); //放大 计算x的y方次 参数都是double类型 } else { s = pow(1 / 1.1, -m_scaleValue); //缩小 } setScale(s); } void PixItem::setZoomState(const int &zoomState) { m_zoomState = zoomState; if (m_zoomState == RESET) { m_scaleValue = 0; setScale(1); setTransformOriginPoint(0, 0); } } int PixItem::getScaleValue() const { return m_scaleValue; }