Qt之简单绘图实现

效果图:

                                            

可以实现打开图片，在打开的图片上画图，可以保存图片，以及橡皮擦，画笔调大调粗换色功能。

代码:

XImage.h:

#ifndef __XIMAGE__H__
#define __XIMAGE__H__
#include "qwidget.h"
#include<QPaintEvent>
#include<QMouseEvent>
#include<QColor>
#include<Qpen>
class XImage :
    public QWidget
{
    Q_OBJECT
public:
    XImage(QWidget* parent=NULL);
    ~XImage();
    void paintEvent(QPaintEvent* ev) override;
    void mouseMoveEvent(QMouseEvent* ev) override;
    void mouseReleaseEvent(QMouseEvent* ev) override;
    public slots:
    void Open();
    void SetPen(int size,QColor col);
    void SetErase(int size);
    void Save();
private:
    QImage src;
    QPoint mpos;
    QPen pen;
    QImage img;
};
#endif

XImage.cpp:

#include "XImage.h"
#include<QFileDialog>
#include "ui_XPS.h"
#include<QPainter>
XImage::XImage(QWidget* parent):QWidget(parent){}

void XImage::Open()
{
    QString filename = QFileDialog::getOpenFileName(this, QStringLiteral("打开图片"),
        "",QStringLiteral("支持格式(*.png *.jpg)"));
    if (filename.isNull())return;
    if (!src.load(filename))return;
    mpos = QPoint();
    img = src.copy();
    update();
}

void XImage::mouseMoveEvent(QMouseEvent* ev)
{
    QPainter painter(&img);
    painter.setPen(pen);
    if (mpos.isNull()) mpos = ev->pos();
    painter.drawLine(QLine(mpos,ev->pos()));
    mpos = ev->pos();
    update();
}

void XImage::SetPen(int size, QColor col)
{
    pen.setWidth(size);
    pen.setColor(col);
    pen.setCapStyle(Qt::RoundCap);
    pen.setJoinStyle(Qt::RoundJoin);
}

void XImage::mouseReleaseEvent(QMouseEvent* ev)
{
    mpos = QPoint();
}

void XImage::paintEvent(QPaintEvent* ev)
{
    QPainter painter(this);
    painter.drawImage(0,0,img);
}

void XImage::SetErase(int size)
{
    pen.setWidth(size);
    pen.setBrush(src);
}

void XImage::Save()
{
    QString filename = QFileDialog::getSaveFileName(this, QStringLiteral("打开图片"),
        "", QStringLiteral("支持格式(*.png *.jpg)"));
    if (filename.isNull())return;
    if (!src.save(filename))return;
}

XImage::~XImage(){}

XSP.h:

#ifndef __XPS__H__
#define __XPS__H__

#include <QtWidgets/QMainWindow>
#include "ui_XPS.h"
#include<QColor>
class XPS : public QMainWindow
{
    Q_OBJECT

public:
    XPS(QWidget *parent = Q_NULLPTR);
public slots:
    void SetPen();
    void SetColor();
    void SetErase();
    void Save();
private:
    Ui::XPSClass ui;
    QColor col;
};
#endif

XSH.cpp:

#include "XPS.h"
#include<QColorDialog>
#include<QButtonGroup>
XPS::XPS(QWidget *parent)
    : QMainWindow(parent)
{
    ui.setupUi(this);

    connect(ui.openaction,SIGNAL(triggered()),ui.Image,SLOT(Open()));
    connect(ui.saveaction,SIGNAL(triggered()),ui.Image,SLOT(Save()));
    col = QColor(250,0,0);
    SetPen();

    QButtonGroup* group = new QButtonGroup(this);
    group->addButton(ui.penButton);
    group->addButton(ui.eraseButton);
    group->setExclusive(true);
}

void XPS::SetPen()
{
    ui.Image->SetPen(ui.pensize->value(),col);
    ui.penButton->setChecked(true);
}

void XPS::SetColor()
{
        col = QColorDialog::getColor(Qt::red, this);
        QString sty = QString("background-color:rgba(%1,%2,%3,%4)")
            .arg(col.red()).arg(col.green()).arg(col.blue()).arg(col.alpha());
        ui.colorButton->setStyleSheet(sty);
        SetPen();
}

void XPS::SetErase()
{
    ui.Image->SetErase(ui.pensize->value());
    ui.eraseButton->setChecked(true);
}

void XPS::Save()
{
    ui.Image->Save();
    ui.statusBar->showMessage(QStringLiteral("保存结束"), 5000);
}

main.cpp:

#include "XPS.h"
#include <QtWidgets/QApplication>

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

ui界面部分:

测试环境：vs2015

可能出现的问题:

要包含该目录: