frame.cpp

#include "frame.h"

#include <QPainter>

frame::frame(QWidget *parent) : QFrame(parent)
{

}

void frame::paintEvent(QPaintEvent *p)
{
    QPainter pPainter(this);
    QImage img(":/left.png");
    Q_ASSERT(!img.isNull());
    QRect source(0,0,20,10);
    QRect target(50,50,20,10);
    pPainter.drawImage(target, img, source);
    QWidget::paintEvent(p);
}

frame.h

#ifndef FRAME_H
#define FRAME_H

#include <QFrame>

class frame : public QFrame
{
    Q_OBJECT
public:
    explicit frame(QWidget *parent = nullptr);
protected:
    void paintEvent(QPaintEvent *p);
};

#endif // FRAME_H

main.cpp

#include "widget.h"
#include <QApplication>

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

resource.qrc

<RCC>
    <qresource prefix="/">
        <file>left.png</file>
    </qresource>
</RCC>

testImage.pro

#-------------------------------------------------
#
# Project created by QtCreator 2017-09-20T10:41:49
#
#-------------------------------------------------

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = testImage
TEMPLATE = app

# The following define makes your compiler emit warnings if you use
# any feature of Qt which has been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0


SOURCES += \
        main.cpp \
        widget.cpp \
    frame.cpp

HEADERS += \
        widget.h \
    frame.h

FORMS += \
        widget.ui

RESOURCES += \
    resource.qrc

widget.cpp

#include "widget.h"
#include "ui_widget.h"

Widget::Widget(QWidget *parent) :
    QFrame(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
}

Widget::~Widget()
{
    delete ui;
}

widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include "frame.h"

#include <QWidget>

namespace Ui {
class Widget;
}

class Widget : public QFrame
{
    Q_OBJECT
public:
    explicit Widget(QWidget *parent = 0);
    ~Widget();

private:
    Ui::Widget *ui;
};

#endif // WIDGET_H

widget.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>Widget</class>
 <widget class="QWidget" name="Widget">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>823</width>
    <height>468</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>Widget</string>
  </property>
  <widget class="frame" name="myFrame">
   <property name="geometry">
    <rect>
     <x>200</x>
     <y>60</y>
     <width>420</width>
     <height>300</height>
    </rect>
   </property>
   <property name="minimumSize">
    <size>
     <width>420</width>
     <height>300</height>
    </size>
   </property>
   <property name="maximumSize">
    <size>
     <width>420</width>
     <height>306</height>
    </size>
   </property>
   <property name="frameShape">
    <enum>QFrame::StyledPanel</enum>
   </property>
   <property name="frameShadow">
    <enum>QFrame::Raised</enum>
   </property>
  </widget>
 </widget>
 <layoutdefault spacing="6" margin="11"/>
 <customwidgets>
  <customwidget>
   <class>frame</class>
   <extends>QFrame</extends>
   <header>frame.h</header>
   <container>1</container>
  </customwidget>
 </customwidgets>
 <resources/>
 <connections/>
</ui>