30 Thread Drawing

Multi-threaded drawing

I've seen it before. The image drawing device can be used in the thread.

This example. A polygon is randomly drawn in the thread, the picture is emitted by the signal, the picture is accepted in the main thread, and drawn in the drawing event.

There is a button in the window that, when clicked, draws a picture in the thread and then displays the drawn picture in the current window.

Sub-threading Random drawing parsing

Class Mythread:public Qobject

{

void DrawImage (); Self-fitting threading functions

Signals:

void UpdateImage (Qimage temp); Self-fitting signal

}

Implementing threading Functions

void MyThread::D rawimage ()

{

Defining IAMGE Drawing Devices

Qimage image (400,400,QIMAGE::FORMAT_ARGB32);

define painter, specify drawing device

Qpainter p (&image);

Defining brushes

Qpen pen;

Pen.setwidth (5); Brush thickness

Pen.setstyle (qt::solidline);//Brush style

Hand the brush to the painter

P.setpen (pen);

Defining a paint brush

Qbrush Brush;

Brush.setstyle (Qt::solidpattern);//Paint brush style

Brush.setcolor (qt::red); Paint Brush Color

Hand the brush to the painter

P.setbrush (brush);

Randomly generate 5 points to form a polygon

Qpoint arr[]=

{

Qpoint (Qrand ()%400,qrand ()%400),

Qpoint (Qrand ()%400,qrand ()%400),

Qpoint (Qrand ()%400,qrand ()%400),

Qpoint (Qrand ()%400,qrand ()%400),

Qpoint (Qrand ()%400,qrand ()%400)

};

Draw polygons

P.drawpolygon (arr,5);

Send a signal and send the picture

Emit updateimage (image);

}

The main thread accepts the picture and draws the picture parsing

Press the button to invoke the thread's thread handler function

Connect (Ui->pushbutton,&qpushbutton::p ressed,m_mythread,&mythread::D rawimage);

Accept the signal and take out the picture

Connect (m_mythread,&mythread::updateimage,this,&widget::getimage);

void Widget::getimage (Qimage temp)

{

M_image=temp; Remove picture

Update (); Update

}

void Widget::p aintevent (qpaintevent *)

{

Drawing

Qpainter p (this);

P.drawimage (100,100,m_image);

}

Source:

Mythread.h

#ifndef Mythread_h

#define Mythread_h

#include <QObject>

#include <QImage>

Class Mythread:public Qobject

{

Q_object

Public

Explicit MyThread (Qobject *parent = 0);

void DrawImage (); Self-fitting threading functions

Signals:

void UpdateImage (Qimage temp); Self-fitting signal

Public Slots:

};

#endif//Mythread_h

Mythread.cpp

#include "Mythread.h"

#include <QPainter>

#include <QPen>

#include <QBrush>

Mythread::mythread (Qobject *parent):

Qobject (parent)

{

}

Implementing threading Functions

void MyThread::D rawimage ()

{

Defining IAMGE Drawing Devices

Qimage image (400,400,QIMAGE::FORMAT_ARGB32);

define painter, specify drawing device

Qpainter p (&image);

Defining brushes

Qpen pen;

Pen.setwidth (5); Brush thickness

Pen.setstyle (qt::solidline);//Brush style

Hand the brush to the painter

P.setpen (pen);

Defining a paint brush

Qbrush Brush;

Brush.setstyle (Qt::solidpattern);//Paint brush style

Brush.setcolor (qt::red); Paint Brush Color

Hand the brush to the painter

P.setbrush (brush);

Randomly generate 5 points to form a polygon

Qpoint arr[]=

{

Qpoint (Qrand ()%400,qrand ()%400),

Qpoint (Qrand ()%400,qrand ()%400),

Qpoint (Qrand ()%400,qrand ()%400),

Qpoint (Qrand ()%400,qrand ()%400),

Qpoint (Qrand ()%400,qrand ()%400)

};

Draw polygons

P.drawpolygon (arr,5);

Send a signal and send the picture

Emit updateimage (image);

}

Widget.h

#ifndef Widget_h

#define Widget_h

#include <QWidget>

#include "Mythread.h"

#include <QPaintEvent>

#include <QThread>

#include <QImage>

Namespace Ui {

Class Widget;

}

Class Widget:public Qwidget

{

Q_object

Public

Explicit Widget (Qwidget *parent = 0);

~widget ();

void PaintEvent (Qpaintevent *); Drawing events

Public Slots:

void GetImage (Qimage temp); Take out a picture with a signal

Signals:

void Startdraw ();

Private

Ui::widget *ui;

MyThread *m_mythread; Custom Thread Objects

Qthread *m_thread; Child threads

Qimage M_image; Image

};

#endif//Widget_h

Widget.cpp

#include "Widget.h"

#include "Ui_widget.h"

#include <QPainter>

Widget::widget (Qwidget *parent):

Qwidget (parent),

UI (New Ui::widget)

{

UI->SETUPUI (this);

This->resize (600,600);

Custom Class object, no parent object can be specified

M_mythread=new MyThread;

Creating Child Threads

M_thread=new Qthread (this);

Attaching a custom module to a child thread

M_mythread->movetothread (M_thread);

Mode two: Use the button to start the thread, and then send a signal to call the thread handler function

Connect (Ui->pushbutton,&qpushbutton::p ressed,

//            [=]()

//            {

M_thread->start ();

Emit Startdraw ();

//            }

//    );

Connect (this,&widget::startdraw,m_mythread,&mythread::D rawimage);

Starts a thread, but does not start a thread-handling function

M_thread->start ();

Press the button to invoke the thread's thread handler function

Connect (Ui->pushbutton,&qpushbutton::p ressed,m_mythread,&mythread::D rawimage);

Accept the signal and take out the picture

Connect (m_mythread,&mythread::updateimage,this,&widget::getimage);

}

Widget::~widget ()

{

Delete UI;

}

void Widget::getimage (Qimage temp)

{

M_image=temp; Remove picture

Update (); Update

}

void Widget::p aintevent (qpaintevent *)

{

Drawing

Qpainter p (this);

P.drawimage (100,100,m_image);

}

30 Thread Drawing