知识点

感觉这个就是在图片背景 贴了白色

shape.h

#ifndef SHAPE_H
#define SHAPE_H

#include <QWidget>


class Shape : public QWidget
{
    Q_OBJECT

public:
    Shape(QWidget *parent = nullptr);
    ~Shape();
protected:
    void mousePressEvent(QMouseEvent*);
    void mouseMoveEvent(QMouseEvent *event);
    void paintEvent(QPaintEvent*);
private:
    QPoint DragPosition;

};
#endif // SHAPE_H

shape.cpp

#include "shape.h"
#include <QMouseEvent>
#include <QPainter>
#include <QPixmap>
#include <QBitmap>


Shape::Shape(QWidget *parent)
    : QWidget(parent)
{
    QPixmap Pix;
    Pix.load("312.ico",0,Qt::AvoidDither|Qt::ThresholdDither|Qt::ThresholdAlphaDither);
    resize(Pix.size());
    setMask(QBitmap(Pix.mask()));

}

Shape::~Shape() {}

void Shape::mousePressEvent(QMouseEvent *Event)
{
    if(Event->button() == Qt::LeftButton)
    {
        DragPosition = Event->globalPos() - frameGeometry().topLeft();
        Event->accept();
    }
    if(Event->button() == Qt::RightButton)
    {
        close();
    }

}

void Shape::mouseMoveEvent(QMouseEvent *Event)
{
    if(Event->buttons()&Qt::LeftButton)
    {
        move(Event->globalPos()-DragPosition);
        Event->accept();
    }
}

void Shape::paintEvent(QPaintEvent*)
{
    QPainter Painter(this);
    Painter.drawPixmap(0,0,QPixmap("312.ico"));

}

main.cpp

#include "shape.h"

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Shape w;
    w.show();
    return a.exec();
}

运行图