qt下如何保持图片用滚轮缩放不失真啊新手请大神指点

qt下怎么保持图片用滚轮缩放不失真啊，新手请大神指点
rt，现在想实现一个功能是缩放能在图片中心位置进行缩放，二是缩放不要失真，不知道为什么总是失真，新手求指导

代码：

#include "kk.h"

KK::KK(QWidget *parent)
    : QWidget(parent,Qt::FramelessWindowHint)
{
    pix.load( "picture.JPG",0,Qt::AvoidDither|Qt::ThresholdDither|Qt::ThresholdAlphaDither);
    resize(pix.size());
   // setMask(pix.mask());
}

void KK::mousePressEvent(QMouseEvent *event)
{
    if (event->button()==Qt::LeftButton)
    {
        point=event->globalPos()-frameGeometry().topLeft();//globalPos()获取根窗口的相对路径，frameGeometry().topLeft获得主窗口左上角的位置
        event->accept();
    }
    if(event->button()==Qt::RightButton)
    {
        close();
    }
}

void KK::mouseMoveEvent(QMouseEvent *event)
{
    if (event->buttons()==Qt::LeftButton)
    {
        move(event->globalPos()-point);
        event->accept();
    }

}

void KK::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    painter.drawPixmap(0,0,pix);//绘制图片到窗口
}

void KK::wheelEvent(QWheelEvent *event)
{
    int numDegrees = event->delta()/8;
    int numSteps=numDegrees/15;
    qreal width = pix.width();
    qreal height = pix.height();
    pix=pix.scaled(width*(1+numSteps*0.15), height*(1+numSteps*0.15), Qt::KeepAspectRatio,Qt::SmoothTransformation);
    resize(pix.size());
}

KK::~KK()
{
    
}

------解决方案--------------------
painter.setRenderHint(QPainter::Antialiasing, true)

会有作用吗
------解决方案--------------------