Qt图形与图片

6.1.1 区别概述

     Qt提供了很多关于获取窗体位置及显示区域大小的函数，如x( )、y( )和pos( )、rect( )、size( )、geometry( )等，统称为“位置相关函数”或“位置函数”。

6.2.1  绘图框架设计

  （1） 利用QPainter绘制图形，基本图形的draw函数

（2）利用QPainterPath绘制简单图形。

     利用QPainterPath绘制简单图形，QPainterPath类为QPainter类提供了一个存储容器，里面包含了所要绘制的内容的集合及绘制的顺序，如长方形、多边形、曲线等各

种任意图形。 cubicTo()函数绘制的是贝赛尔曲线

     利用QPainterPath类可以实现QPainter类的draw()函数能够实现的所有图形。例如，对于QPainter::drawRect()函数，除了可用上面介绍的QPainterPath::addRect()的方式实现，还可以用如下方式实现：

     QPainterPathpath;

     path.moveTo(0,0);

     path.lineTo(200,0);

     path.lineTo(200,100);

     path.lineTo(0,100);

     path.lineTo(0,0);

其中，

     lshapeComboBox->addItem(tr("Line"),PaintArea::Line)：QComboBox的addItem()函数可以仅插入文本，也可同时插入与文本相对应的具体数据，

通常为枚举型数据，便于后面操作时确定选择的是哪个数据。

     lpenStyleComboBox->addItem(tr("SolidLine"),static_cast<int>(Qt::SolidLine))：选用不同的参数，对应画笔的不同风格。

     l penCapComboBox->addItem(tr("SquareCap"),Qt::SquareCap)：选用不同的参数，对应画笔顶帽的不同风格

     l penJoinComboBox->addItem(tr("BevelJoin"),Qt::BevelJoin)：选用不同的参数，对应画笔连接点的不同风格

     l fillRuleComboBox->addItem(tr("Odd Even"),Qt::OddEvenFill)：Qt为QPainterPath类提供了两种填充规则，分别是Qt::OddEvenFill和Qt::WindingFill

     其中，Qt::OddEvenFill填充规则判断的依据是从图形中某一点画一条水平线到图形外，若这条水平线与图形边线的交点数目为奇数，则说明此点位于图形的内部；

若交点数目为偶数，则此点位于图形的外部

     而Qt::WindingFill填充规则的判断依据则是从图形中某一点画一条水平线到图形外，每个交点外边线的方向可能向上，也可能向下，将这些交点数累加，方向相反

的相互抵消，若最后结果不为0则说明此点在图形内，若最后结果为0则说明在图形外

      l spreadComboBox->addItem(tr("PadSpread"),QGradient::PadSpread)：铺展效果有三种，分别为QGradient::PadSpread、QGradient::RepeatSpread和QGradient::ReflectSpread。其中，PadSpread是默认的铺展效果，也是最常见的铺展效果，没有被渐变覆盖的区域

填充单一的起始颜色或终止颜色；RepeatSpread效果与ReflectSpread效果只对线性渐变和圆形渐变起作用

     l brushStyleComboBox->addItem(tr("SolidPattern"),static_cast<int>(Qt::SolidPattern))：选用不同的参数，对应画刷的不同风格

项目运行效果

paintarea.h

#ifndef PAINTAREA_H

#define PAINTAREA_H

#include <QWidget>

#include <QPen>

#include <QBrush>

class PaintArea : public QWidget

{

    Q_OBJECT

public:

    explicit PaintArea(QWidget *parent = 0);

    enum Shape{Line, Rectangle, RoundRect, Ellipse, Polygon,

              Polyline, Points, Arc, Path, Text, Pixmap};

    void setShape(Shape);   //设置形状

    void setPen(QPen);      //设置画笔

    void setBrush(QBrush);  //设置画刷

    void setFillRule(Qt::FillRule); //设置填充模式

    void paintEvent (QPaintEvent *);  //设置重画模式

signals:

public slots:

private:

    Shape shape;

    QPen pen;

    QBrush brush;

    Qt::FillRule fillRule;

};

#endif // PAINTAREA_H

paintarea.cpp

#include "paintarea.h"

#include <QPainter>

/*

 * 设置图形显示区域的背景色及最小显示尺寸

*/

PaintArea::PaintArea(QWidget *parent) : QWidget(parent)

{

    setPalette (QPalette(Qt::white));

    setAutoFillBackground (true);

    setMinimumSize (400, 400);

}

void PaintArea::setShape (Shape s)

{

    shape = s;

    update ();

}

void PaintArea::setPen (QPen p)

{

    pen = p;

    update ();

}

void PaintArea::setBrush (QBrush b)

{

    brush = b;

    update();

}

void PaintArea::setFillRule (Qt::FillRule rule)

{

    fillRule = rule;

    update ();

}

/*

 * 重新绘制窗体

*/

void PaintArea::paintEvent (QPaintEvent *)

{

    QPainter p(this);

    p.setPen (pen);

    p.setBrush (brush);

    QRect rect(50, 100, 300, 200);  //设定一个长方形区域

    static const QPoint points[4] = //创建一个QPoint的数组，包含四个点，为画多边形，多边线及点做准备

    {

        QPoint(150, 100),

        QPoint(300, 150),

        QPoint(350, 250),

        QPoint(100, 300)

    };

    int startAngle = 30 * 16;           //设置弧线的起始角度

    int spanAngle = 120 * 16;           //设置弧线的结束角度

    QPainterPath path;                  //新建一个QPainterPath对象为画路径做准备

    path.addRect (150, 150, 100, 100);  //x, y, w, h

    path.moveTo (100, 100);             //将坐标移动到（100 100）位置

    //绘制贝塞尔曲线

    path.cubicTo (300, 100, 200, 200, 300, 300);

    path.cubicTo (100, 300, 200, 200, 100, 100);

    path.setFillRule (fillRule);        //调用填充模式函数

    switch(shape)

    {

    case Line:      //直线

        p.drawLine (rect.topLeft (), rect.bottomRight ()); break;

    case Rectangle: //长方形

        p.drawRect (rect); break;

    case RoundRect: //圆角长方形

        p.drawRoundRect (rect); break;

    case Ellipse:   //椭圆形

        p.drawEllipse (rect); break;

    case Polygon:   //多边形

        p.drawPolygon (points, 4); break;

    case Polyline:  //点

        p.drawPoints (points, 4); break;

    case Arc:       //弧

        p.drawArc (rect, startAngle, spanAngle); break;

    case Path:      //路径

        p.drawPath (path);  break;

    case Text:      //文字

        p.drawText (rect, Qt::AlignCenter, tr("Hello Qt word!")); break;

    case Pixmap:

        p.drawPixmap (150, 150, QPixmap("butterfly.png")); break;

    default:

        break;

    }

}

mainwidget.h

#ifndef MAINWIDGET_H

#define MAINWIDGET_H

#include <QWidget>

#include <QLabel>

#include <QComboBox>

#include <QSpinBox>

#include <QPushButton>

#include <QGridLayout>

#include <QGradient>

#include "paintarea.h"

class MainWidget : public QWidget

{

    Q_OBJECT

public:

    MainWidget(QWidget *parent = 0);

    ~MainWidget();

private:

    PaintArea *paintArea;

    QLabel *shapeLabel;         //形状标签

    QComboBox *shapeComboBox;   //形状下拉框

    QLabel *penColorLabel;      //画笔颜色标签

    QFrame *penColorFrame;      //画笔颜色画板

    QPushButton *penColorBtn;   //画笔颜色按钮

    QLabel *penWidthLabel;      //画笔宽度标签

    QSpinBox *penWidthSpinBox;  //画笔宽度数字显示框

    QLabel *penStyleLabel;      //画板风格标签

    QComboBox *penStyleComboBox;//画笔风格下拉框

    QLabel *penCapLabel;        //画笔顶帽标签

    QComboBox *penCapComboBox;  //画笔顶帽下拉框

    QLabel  *penJoinLabel;      //画笔连接点标签

    QComboBox *penJoinComboBox; //画笔连接点下拉框

    QLabel *fillRuleLabel;      //填充模式标签

    QComboBox *fillRuleComboBox;//填充模式下拉框

    QLabel *spreadLabel;        //铺展效果标签

    QComboBox *spreadComboBox;  //铺展效果下拉框

    QGradient::Spread spread;   //

    QLabel *brushColorLabel;    //笔刷颜色标签

    QComboBox *brushColorComboBox;  //笔刷颜色下拉框

    QFrame *brushColorFrame;        //笔刷颜色风格

    QPushButton *brushColorBtn; //笔刷颜色按钮

    QLabel *brushStyleLabel;    //笔刷风格标签

    QComboBox *brushStyleComboBox;  //笔刷风格下拉框

    QGridLayout *rightLayout;   //右侧布局指针

protected slots:

    void showshape(int);        //显示图形

    void showpencolor();        //显示画笔颜色

    void showpenwidth(int);     //显示画笔宽度

    void showpenstyle(int);     //显示画笔风格

    void showpencap(int);       //显示画笔顶帽

    void showpenjoin(int);      //显示画笔连接点

    void showfillrule();        //显示填充颜色

    void showspreadstyle();     //显示铺展效果

    void showbrushcolor();      //显示画刷颜色

    void showbrushstyle(int);   //显示画刷风格

};

#endif // MAINWIDGET_H

mainwidget.cpp

#include "mainwidget.h"

#include <QColorDialog>

MainWidget::MainWidget(QWidget *parent)

    : QWidget(parent)

{

    paintArea = new PaintArea;

    shapeLabel = new QLabel(tr("形状:"));

    shapeComboBox = new QComboBox;

    shapeComboBox->addItem (tr("Line"), PaintArea::Line);

    shapeComboBox->addItem (tr("Rectangle"), PaintArea::Rectangle);

    shapeComboBox->addItem (tr("RoundedRect"), PaintArea::RoundRect);

    shapeComboBox->addItem (tr("Ellipse"), PaintArea::Ellipse);

    shapeComboBox->addItem (tr("Polygon"), PaintArea::Polygon);

    shapeComboBox->addItem (tr("Polyline"), PaintArea::Polyline);

    shapeComboBox->addItem (tr("Points"), PaintArea::Points);

    shapeComboBox->addItem (tr("Arc"), PaintArea::Arc);

    shapeComboBox->addItem (tr("Path"), PaintArea::Path);

    shapeComboBox->addItem (tr("Text"), PaintArea::Text);

    shapeComboBox->addItem (tr("Pixmap"), PaintArea::Pixmap);

    connect (shapeComboBox, SIGNAL(activated(int)), this, SLOT(showshape(int)));

    //设置画笔颜色

    penColorLabel = new QLabel(tr("画笔颜色:"));

    penColorFrame = new QFrame;

    penColorFrame->setFrameStyle (QFrame::Panel | QFrame::Sunken);

    penColorFrame->setAutoFillBackground (true);            //设置自动填充背景色

    penColorFrame->setPalette (QPalette(Qt::blue));         //画板初始颜色蓝色

    penColorBtn = new QPushButton(tr("更改"));

    connect (penColorBtn, SIGNAL(clicked(bool)), this, SLOT(showpencolor()));

    //设置画笔宽度

    penWidthLabel = new QLabel(tr("画笔宽度:"));

    penWidthSpinBox = new QSpinBox;

    penWidthSpinBox->setRange (0, 20);

    connect (penWidthSpinBox, SIGNAL(valueChanged(int)), this, SLOT(showpenwidth(int)));

    //设置画笔风格

    penStyleLabel = new QLabel(tr("画笔风格:"));

    penStyleComboBox = new QComboBox;

    penStyleComboBox->addItem(tr("SolidLine"),static_cast<int>(Qt::SolidLine));

    penStyleComboBox->addItem(tr("DashLine"),static_cast<int>(Qt::DashLine));

    penStyleComboBox->addItem(tr("DotLine"),static_cast<int>(Qt::DotLine));

    penStyleComboBox->addItem(tr("DashDotLine"),static_cast<int>(Qt::DashDotLine));

    penStyleComboBox->addItem(tr("DashDotDotLine"),static_cast<int>(Qt::DashDotDotLine));

    penStyleComboBox->addItem(tr("CustomDashLine"),static_cast<int>(Qt::CustomDashLine));

    connect(penStyleComboBox,SIGNAL(activated(int)),this,SLOT (showpenstyle(int)));

    //设置画笔顶帽

    penCapLabel = new QLabel(tr("画笔顶帽:"));

    penCapComboBox = new QComboBox;

    penCapComboBox->addItem (tr("SquareCap"), Qt::SquareCap);

    penCapComboBox->addItem (tr("FlatCap"), Qt::FlatCap);

    penCapComboBox->addItem (tr("RoundCap"), Qt::RoundCap);

    connect (penCapComboBox, SIGNAL(activated(int)), this, SLOT(showpencap(int)));

    //设置画笔连接点

    penJoinLabel  = new QLabel(tr("画笔连接点:"));

    penJoinComboBox = new QComboBox;

    penJoinComboBox->addItem (tr("BevelJoin"), Qt::BevelJoin);

    penJoinComboBox->addItem (tr("MiterJoin"), Qt::MiterJoin);

    penJoinComboBox->addItem (tr("RoundJoin"), Qt::RoundJoin);

    connect(penJoinComboBox, SIGNAL(activated(int)), this, SLOT(showpenjoin(int)));

    //设置填充模式

    fillRuleLabel = new QLabel(tr("填充模式:"));

    fillRuleComboBox = new QComboBox;

    fillRuleComboBox->addItem (tr("Odd Even"), Qt::OddEvenFill);

    fillRuleComboBox->addItem (tr("Winding"), Qt::WindingFill);

    connect (fillRuleComboBox, SIGNAL(activated(int)), this, SLOT(showfillrule()));

    //设置铺展效果

    spreadLabel = new QLabel(tr("铺展效果:"));

    spreadComboBox = new QComboBox;

    spreadComboBox->addItem (tr("PadSpread"), QGradient::PadSpread);

    spreadComboBox->addItem (tr("RepeatSpread"), QGradient::RepeatSpread);

    spreadComboBox->addItem(tr("ReflectSpread"),QGradient:: ReflectSpread);

    connect(spreadComboBox,SIGNAL(activated(int)),this,SLOT (showspreadstyle()));

    //设置画刷颜色

    brushColorLabel = new QLabel(tr("画刷颜色："));        //画刷颜色选择控件

    brushColorFrame = new QFrame;

    brushColorFrame->setFrameStyle(QFrame::Panel|QFrame::Sunken);

    brushColorFrame->setAutoFillBackground(true);

    brushColorFrame->setPalette(QPalette(Qt::green));

    brushColorBtn =new QPushButton(tr("更改"));

    connect(brushColorBtn,SIGNAL(clicked()),this,SLOT (showbrushcolor()));

    //设置画刷风格

    brushStyleLabel =new QLabel(tr("画刷风格："));      //画刷风格选择下拉列表框

    brushStyleComboBox =new QComboBox;

    brushStyleComboBox->addItem(tr("SolidPattern"),static_cast<int>(Qt::SolidPattern));

    brushStyleComboBox->addItem(tr("Dense1Pattern"),static_cast<int>(Qt::Dense1Pattern));

    brushStyleComboBox->addItem(tr("Dense2Pattern"),static_cast<int>(Qt::Dense2Pattern));

    brushStyleComboBox->addItem(tr("Dense3Pattern"),static_cast<int>(Qt::Dense3Pattern));

    brushStyleComboBox->addItem(tr("Dense4Pattern"),static_cast<int>(Qt::Dense4Pattern));

    brushStyleComboBox->addItem(tr("Dense5Pattern"),static_cast<int>(Qt::Dense5Pattern));

    brushStyleComboBox->addItem(tr("Dense6Pattern"),static_cast<int>(Qt::Dense6Pattern));

    brushStyleComboBox->addItem(tr("Dense7Pattern"),static_cast<int>(Qt::Dense7Pattern));

    brushStyleComboBox->addItem(tr("HorPattern"),static_cast<int>(Qt::HorPattern));

    brushStyleComboBox->addItem(tr("VerPattern"),static_cast<int>(Qt::VerPattern));

    brushStyleComboBox->addItem(tr("CrossPattern"),static_cast<int>(Qt::CrossPattern));

    brushStyleComboBox->addItem(tr("BDiagPattern"),static_cast<int>(Qt::BDiagPattern));

    brushStyleComboBox->addItem(tr("FDiagPattern"),static_cast<int>(Qt::FDiagPattern));

    brushStyleComboBox->addItem(tr("DiagCrossPattern"),static_cast<int>(Qt:: DiagCrossPattern));

    brushStyleComboBox->addItem(tr("LinearGradientPattern"),static_cast<int>(Qt:: LinearGradientPattern));

    brushStyleComboBox->addItem(tr("ConicalGradientPattern"),static_cast<int>(Qt:: ConicalGradientPattern));

    brushStyleComboBox->addItem(tr("RadialGradientPattern"),static_cast<int>(Qt:: RadialGradientPattern));

    brushStyleComboBox->addItem(tr("TexturePattern"),static_cast<int>(Qt::TexturePattern));

    connect(brushStyleComboBox,SIGNAL(activated(int)),this,SLOT (showbrushstyle(int)));

    rightLayout = new QGridLayout;  //控制面板布局

    rightLayout->addWidget(shapeLabel,0,0);

    rightLayout->addWidget(shapeComboBox,0,1);

    rightLayout->addWidget(penColorLabel,1,0);

    rightLayout->addWidget(penColorFrame,1,1);

    rightLayout->addWidget(penColorBtn,1,2);

    rightLayout->addWidget(penWidthLabel,2,0);

    rightLayout->addWidget(penWidthSpinBox,2,1);

    rightLayout->addWidget(penStyleLabel,3,0);

    rightLayout->addWidget(penStyleComboBox,3,1);

    rightLayout->addWidget(penCapLabel,4,0);

    rightLayout->addWidget(penCapComboBox,4,1);

    rightLayout->addWidget(penJoinLabel,5,0);

    rightLayout->addWidget(penJoinComboBox,5,1);

    rightLayout->addWidget(fillRuleLabel,6,0);

    rightLayout->addWidget(fillRuleComboBox,6,1);

    rightLayout->addWidget(spreadLabel,7,0);

    rightLayout->addWidget(spreadComboBox,7,1);

    rightLayout->addWidget(brushColorLabel,8,0);

    rightLayout->addWidget(brushColorFrame,8,1);

    rightLayout->addWidget(brushColorBtn,8,2);

    rightLayout->addWidget(brushStyleLabel,9,0);

    rightLayout->addWidget(brushStyleComboBox,9,1);

    QHBoxLayout *mainLayout = new QHBoxLayout(this);    //整体布局

    mainLayout->addWidget (paintArea);

    mainLayout->addLayout (rightLayout);

    mainLayout->setStretchFactor (paintArea, 1);

    mainLayout->setStretchFactor (rightLayout, 0);

    showshape (shapeComboBox->currentIndex ());         //显示默认图形

}

MainWidget::~MainWidget()

{

}

void MainWidget::showshape (int value)

{

    PaintArea::Shape shape = PaintArea::Shape(shapeComboBox->itemData (value, Qt::UserRole).toInt ());

    paintArea->setShape (shape);

}

void MainWidget::showpencolor ()

{

    QColor color = QColorDialog::getColor(static_cast<int>(Qt::blue));

    penColorFrame->setPalette(QPalette(color));

    int value = penWidthSpinBox->value();

    Qt::PenStyle style = Qt::PenStyle(penStyleComboBox->itemData(penStyleComboBox->currentIndex(),Qt::UserRole).toInt());

    Qt::PenCapStyle cap = Qt::PenCapStyle(penCapComboBox->itemData(penCapComboBox->currentIndex(),Qt::UserRole).toInt());

    Qt::PenJoinStyle join=Qt::PenJoinStyle(penJoinComboBox->itemData(penJoinComboBox->currentIndex(),Qt::UserRole).toInt());

    paintArea->setPen(QPen(color,value,style,cap,join));

}

void MainWidget::showpenwidth (int value)

{

    QColor color = penColorFrame->palette ().color (QPalette::Window);

    Qt::PenStyle style = Qt::PenStyle(penStyleComboBox->itemData(penStyleComboBox->currentIndex(),Qt::UserRole).toInt());

    Qt::PenCapStyle cap = Qt::PenCapStyle(penCapComboBox->itemData(penCapComboBox->currentIndex(),Qt::UserRole).toInt());

    Qt::PenJoinStyle join=Qt::PenJoinStyle(penJoinComboBox->itemData(penJoinComboBox->currentIndex(),Qt::UserRole).toInt());

    paintArea->setPen(QPen(color,value,style,cap,join));

}

void MainWidget::showpenstyle (int stylevalue)

{

    QColor color = penColorFrame->palette ().color (QPalette::Window);

    int value = penWidthSpinBox->value ();

    Qt::PenStyle style = Qt::PenStyle(penStyleComboBox->itemData (stylevalue, Qt::UserRole).toInt ());

    Qt::PenCapStyle cap = Qt::PenCapStyle(penCapComboBox->itemData (penCapComboBox->currentIndex (), Qt::UserRole).toInt ());

    Qt::PenJoinStyle join = Qt::PenJoinStyle(penJoinComboBox->itemData (penJoinComboBox->currentIndex (), Qt::UserRole).toInt ());

    paintArea->setPen (QPen(color, value, style, cap, join));

}

void MainWidget::showpencap (int capvalue)

{

    QColor color = penColorFrame->palette().color(QPalette::Window);

    int value = penWidthSpinBox->value();

    Qt::PenStyle style = Qt::PenStyle(penStyleComboBox->itemData(penStyleComboBox->currentIndex(),Qt::UserRole).toInt());

    Qt::PenCapStyle cap = Qt::PenCapStyle(penCapComboBox->itemData(capvalue,Qt::UserRole).toInt());

    Qt::PenJoinStyle join=Qt::PenJoinStyle(penJoinComboBox->itemData(penJoinComboBox->currentIndex(),Qt::UserRole).toInt());

    paintArea->setPen(QPen(color,value,style,cap,join));

}

void MainWidget::showpenjoin (int joinvalue)

{

    QColor color = penColorFrame->palette().color(QPalette::Window);

    int value = penWidthSpinBox->value();

    Qt::PenStyle style = Qt::PenStyle(penStyleComboBox->itemData(penStyleComboBox->currentIndex(),Qt::UserRole).toInt());

    Qt::PenCapStyle cap = Qt::PenCapStyle(penCapComboBox->itemData(penCapComboBox->currentIndex(),Qt::UserRole).toInt());

    Qt::PenJoinStyle join=Qt::PenJoinStyle(penJoinComboBox->itemData(joinvalue,Qt::UserRole).toInt());

    paintArea->setPen(QPen(color,value,style,cap,join));

}

void MainWidget::showfillrule ()

{

    Qt::FillRule rule = Qt::FillRule(fillRuleComboBox->itemData (fillRuleComboBox->currentIndex (), Qt::UserRole).toInt ());

    paintArea->setFillRule (rule);

}

void MainWidget::showspreadstyle ()

{

    spread = QGradient::Spread(spreadComboBox->itemData (spreadComboBox->currentIndex (), Qt::UserRole).toInt ());

}

void MainWidget::showbrushcolor ()

{

    QColor color = QColorDialog::getColor (static_cast<int>(Qt::blue));

    brushColorFrame->setPalette (QPalette(color));

    showbrushstyle (brushStyleComboBox->currentIndex ());

}

void MainWidget::showbrushstyle (int value)

{

    QColor color = brushColorFrame->palette().color(QPalette::Window);

    Qt::BrushStyle style = Qt::BrushStyle(brushStyleComboBox->itemData(value,Qt::UserRole).toInt());

    //线性渐变

    if(style == Qt::LinearGradientPattern)

    {

        QLinearGradient linearGradient(0,0,400,400);

        linearGradient.setColorAt(0.0,Qt::white);

        linearGradient.setColorAt(0.2,color);

        linearGradient.setColorAt(1.0,Qt::black);

        linearGradient.setSpread(spread);

        paintArea->setBrush(linearGradient);

    }//圆形渐变

    else if(style == Qt::RadialGradientPattern)

    {

        QRadialGradient radialGradient(200,200,150,150,100);

        radialGradient.setColorAt(0.0,Qt::white);

        radialGradient.setColorAt(0.2,color);

        radialGradient.setColorAt(1.0,Qt::black);

        radialGradient.setSpread(spread);

        paintArea->setBrush(radialGradient);

    }//锥形渐变

    else if(style == Qt::ConicalGradientPattern)

    {

        QConicalGradient conicalGradient(200,200,30);

        conicalGradient.setColorAt(0.0,Qt::white);

        conicalGradient.setColorAt(0.2,color);

        conicalGradient.setColorAt(1.0,Qt::black);

        paintArea->setBrush(conicalGradient);

    }//纹理渐变

    else if(style == Qt::TexturePattern)

    {

        paintArea->setBrush(QBrush(QPixmap("butterfly.png")));

    }

    else

    {

        paintArea->setBrush(QBrush(color,style));

    }

}

main.cpp

#include "mainwidget.h"

#include <QApplication>

#include <QFont>

int main(int argc, char *argv[])

{

    QApplication a(argc, argv);

    QFont f("ZYSong18030", 12);

    a.setFont (f);

    MainWidget w;

    w.show();

    return a.exec();

}

6.3 Qt5的双缓存机制

     

     QMainWindow对象作为主窗口，QToolBar对象作为工具栏，QWidget对象作为主窗口的中央窗体centralWidget，也就是绘图区

运行效果

drawwidget.h

#ifndef DRAWWIDGET_H

#define DRAWWIDGET_H

#include <QWidget>

#include <QPixmap>

#include <QPoint>

#include <QPainter>

#include <QPalette>

class DrawWidget : public QWidget

{

    Q_OBJECT

public:

    explicit DrawWidget(QWidget *parent = 0);

    void mousePressEvent (QMouseEvent *);

    void mouseMoveEvent (QMouseEvent *);

    void paintEvent (QPaintEvent *);

    void resizeEvent (QResizeEvent *);

signals:

public slots:

    void setstyle(int);

    void setwidth(int);

    void setcolor(QColor);

    void clear();

private :

    QPixmap *pix;       //定义一个画板指针

    QPoint startpos;

    QPoint endpos;

    int style;

    int weight;

    QColor color;

};

#endif // DRAWWIDGET_H

drawwidget.cpp

#include "drawwidget.h"

#include <QtGui>

#include <QPen>

DrawWidget::DrawWidget(QWidget *parent) : QWidget(parent)

{

    setAutoFillBackground (true);   //设置窗体背景色

    setPalette (QPalette(Qt::white));

    pix = new QPixmap(size());      //此QPixmap对象用来准备随时接受绘制的内容

    pix->fill (Qt::white);          //填充背景色为白色

    setMinimumSize (600, 400);      //设置绘制区窗体的最小尺寸

}

/*

 * 接收主窗体传来的线性风格参数

*/

void DrawWidget::setstyle (int s)

{

    style = s;

}

/*

 * 接收主窗体传来的线宽数值

*/

void DrawWidget::setwidth (int w)

{

    weight = w;

}

/*

 * 接收主窗体传来的画笔颜色值

*/

void DrawWidget::setcolor (QColor c)

{

    color = c;

}

void DrawWidget::mousePressEvent (QMouseEvent *e)

{

    startpos = e->pos();

}

/*

 * 鼠标一旦移动就更新画笔的风格、宽度、颜色

 * 开始绘制、首先获取画笔、设置画笔、绘画

 * 绘制完后跟新startpos位置

 *

*/

void DrawWidget::mouseMoveEvent (QMouseEvent *e)

{

    QPainter *painter = new QPainter;

    QPen pen;

    pen.setStyle ((Qt::PenStyle)style);

    pen.setWidth (weight);

    pen.setColor (color);

    painter->begin (pix);

    painter->setPen (pen);

    painter->drawLine (startpos, e->pos ());

    painter->end ();

    startpos = e->pos ();   //更新鼠标的位置

    update ();

}

/*

 * 重画函数paintEvent()完成绘制窗体的更新工作，只需调用drawPixmap()

 * 函数将用于接收图形绘制的QPixmap对象绘制在绘制区窗体控件上即可。

*/

void DrawWidget::paintEvent (QPaintEvent *)

{

    QPainter painter(this);

    painter.drawPixmap (QPoint(0, 0), *pix);

}

/*

 * 当窗体的大小发生变化时，效果看起来虽然像是绘制区大小改变了，但实际能够进行绘制的区域仍然没有改变

 * 因为绘图的大小并没有改变，还是原来绘制窗口的大小，所以在窗体尺寸变化时应及时调整用于绘制的QPixmap

 * 对象的尺寸大小

 * 首先判断改变窗口的大小是否大于原窗体的长和宽

 * 创建一个新的QPixmap对象，填充新QPixmap对象的newPix的颜色为白色背景色

 * 新创建的p画笔指向newPix画布里面

 * 在newPix中绘制原pix中的内容

 * 将newPix赋值给pix作为新的绘制图形接收对象

*/

void DrawWidget::resizeEvent (QResizeEvent *event)

{

    if(height () > pix->height () || width() > pix->width ())

    {

        QPixmap *newPix = new QPixmap(size());

        newPix->fill (Qt::white);

        QPainter p(newPix);

        p.drawPixmap (QPoint(0, 0), *pix);

        pix = newPix;

    }

    QWidget::resizeEvent(event);

}

/*

 * 清除函数只需调用一个新的、干净的QPixmap对象代替pix，并调用update()重绘即可

*/

void DrawWidget::clear ()

{

    QPixmap *clearPix = new QPixmap(size());

    clearPix->fill (Qt::white);

    pix = clearPix;

    update ();

}

mainwindow.h

#ifndef MAINWINDOW_H

#define MAINWINDOW_H

#include <QMainWindow>

#include <QLabel>

#include <QComboBox>

#include <QSpinBox>

#include <QToolButton>

#include "drawwidget.h"

class MainWindow : public QMainWindow

{

    Q_OBJECT

public:

    MainWindow(QWidget *parent = 0);

    ~MainWindow();

    void createToolBar();   //创建工具栏

public slots:

    void showstyle();

    void showcolor();

private:

    DrawWidget *drawWidget;

    QLabel *styleLabel;

    QComboBox *styleComboBox;

    QLabel *widthLabel;

    QSpinBox *widthSpinBox;

    QToolButton *colorBtn;

    QToolButton *clearBtn;

};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"

#include <QToolBar>

#include <QColorDialog>

MainWindow::MainWindow(QWidget *parent)

    : QMainWindow(parent)

{

    drawWidget = new DrawWidget;    //新建一个drawWidget对象

    setCentralWidget (drawWidget);  //新建的drawWidget对象作为主窗口的中央窗口

    createToolBar ();               //创建一个工具栏

    setMinimumSize (600, 400);      //设置主窗体的最小尺寸

    showstyle ();       //初始化线型，设置控件中当前值作为初始值

    drawWidget->setwidth (widthSpinBox->value ());  //设置初始线宽

    drawWidget->setcolor (Qt::black);               //设置初始颜色

}

MainWindow::~MainWindow()

{

}

void MainWindow::createToolBar ()

{

    QToolBar *toolBar = addToolBar (tr("Tool"));   //为主窗口创建一个工具栏对象

    styleLabel = new QLabel(tr("线型风格"));

    styleComboBox = new QComboBox;

    styleComboBox->addItem (tr("SolidLine"), static_cast<int>(Qt::SolidLine));

    styleComboBox->addItem (tr("DashLine"), static_cast<int>(Qt::DashLine));

    styleComboBox->addItem (tr("DotLine"), static_cast<int>(Qt::DotLine));

    styleComboBox->addItem (tr("DashDotLine"), static_cast<int>(Qt::DashDotLine));

    styleComboBox->addItem (tr("DashDotDotLine"), static_cast<int>(Qt::DashDotDotLine));

    connect (styleComboBox, SIGNAL(activated(int)), this, SLOT(showstyle()));

    widthLabel = new QLabel(tr("线宽"));

    widthSpinBox = new QSpinBox;

    connect (widthSpinBox, SIGNAL(valueChanged(int)), drawWidget, SLOT(setwidth(int)));

    colorBtn = new QToolButton;

    QPixmap pixmap(20, 20);

    pixmap.fill (Qt::black);

    colorBtn->setIcon (QIcon(pixmap));

    connect (colorBtn, SIGNAL(clicked(bool)), this, SLOT(showcolor()));

    clearBtn = new QToolButton;

    clearBtn->setText (tr("清除"));

    connect (clearBtn, SIGNAL(clicked(bool)), drawWidget, SLOT(clear()));

    toolBar->addWidget (styleLabel);

    toolBar->addWidget (styleComboBox);

    toolBar->addWidget (widthLabel);

    toolBar->addWidget (widthSpinBox);

    toolBar->addWidget (colorBtn);

    toolBar->addWidget (clearBtn);

}

void MainWindow::showstyle ()

{

    drawWidget->setstyle (styleComboBox->itemData (styleComboBox->currentIndex (), Qt::UserRole).toInt ());

}

void MainWindow::showcolor ()

{

    QColor color = QColorDialog::getColor (static_cast<int>(Qt::black), this);

    //判断颜色是否有效

    if(color.isValid ())

    {

        drawWidget->setcolor (color);

        QPixmap p(20, 20);

        p.fill (color);

        colorBtn->setIcon (QIcon(p));

    }

}

main.cpp

#include "mainwindow.h"

#include <QApplication>

int main(int argc, char *argv[])

{

    QApplication a(argc, argv);

    MainWindow w;

    w.show();

    return a.exec();

}

6.4 Qt5 SVG格式图片的显示

SVG格式的特点如下：

（1）基于XML

（2）采用文本来描述对象

（3）具有交互性和动态性

（4）完全支持DOM

SVG相对于GIF，JPEG格式的优势，SVG是一种矢量图形格式，比GIF，JPEG等栅格格式具有众多优势，如文件小，对于网络而言下载速度快；可以任意缩放而不会破坏

图像的清晰度和细节；图像中的文字独立相对于图像，文字保留可编辑和可搜寻的状态，也没有字体的限制，用户系统即使没有安装某一种字体，也可看到与制作时完

全相同的画面等。

下面通过利用QSvgWidget类和QSvgRender类实现一个SVG图片浏览器

Qt5SVG格式图片的显示由三个层次的窗体构成

在完成此功能的程序中使用与SVG相关的类，必须在程序中包含SVG相关的头文件：

#include <QtSvg>

由于Qt默认生成的Makefile中只加入了QtGui、QtCore模块的库，所以必须在工程文件“.pro”中加入一行代码：

QT +=svg

svgwidget.h

#ifndef SVGWIDGET_H

#define SVGWIDGET_H

#include <QtSvg/QtSvg>

#include <QtSvg/QSvgWidget>

#include <QtSvg/QSvgRenderer>

/*

 * SvgWidget继承QSvgWidget，完成具体的SVG图片的显示工作

*/

class SvgWidget : public QSvgWidget

{

    Q_OBJECT

public:

    SvgWidget(QWidget *parent = 0);

    void wheelEvent(QWheelEvent *); //响应鼠标的滚轮事件，是SVG图片能够通过鼠标滚轮的滚动进行缩放

private:

    QSvgRenderer *render;           //用于图片显示尺寸的确定

};

#endif // SVGWIDGET_H

svgwidget.cpp

#include "svgwidget.h"

SvgWidget::SvgWidget(QWidget *parent)

    :QSvgWidget(parent)

{

    render = renderer ();   //获得图片显示的尺寸

}

/*

 * diff的值表示每次滑轮滚动一定的值，图片大小改变的比例

 * render->defaultSize ()获取图片显示区的尺寸大小

 * e->delta()利用QWheelEvent的delta()函数获得滚动滚轮的距离值，通过此值判断滚轮的方向

 * 滚轮向前移动图片长宽增加

 * 滚轮向后移动图片长宽减小

 * 重置图片的长宽

*/

void SvgWidget::wheelEvent (QWheelEvent *e)

{

    const double diff = 0.1;

    QSize size = render->defaultSize ();

    int width = size.width ();

    int height = size.height ();

    if(e->delta () > 0)

    {

        width = int(this->width () + this->width () * diff);

        height = int(this->height () + this->height () * diff);

    }

    else

    {

        width = int(this->width () - this->width () * diff);

        height = int(this->height () - this->height () * diff);

    }

    resize(width, height);      //利用新的长、宽值对图片进行resize()操作

}

svgwindow.h

#ifndef SVGWINDOW_H

#define SVGWINDOW_H

/*

 * SvgWindow继承自QScrollArea类，实现一个带滑动条的显示区域

*/

#include <QScrollArea>

#include "svgwidget.h"

#include <QMenuBar>

class SvgWindow : public QScrollArea

{

    Q_OBJECT

public:

    SvgWindow(QWidget *parent = 0);

    void setFile(QString);

    void mousePressEvent (QMouseEvent *);   //鼠标按下函数

    void mouseMoveEvent (QMouseEvent *);    //鼠标移动函数

private:

    SvgWidget *svgWidget;

    QPoint mousePressPos;               //鼠标按下的位置

    QPoint scrollBarValueOnMousePress;  //鼠标按下是的滚动值

};

#endif // SVGWINDOW_H

svgwindow.cpp

#include "svgwindow.h"

/*

 * 设置滚动条的窗口，使SvgWidget成为SvgWindow的子窗口

*/

SvgWindow::SvgWindow(QWidget *parent)

    : QScrollArea(parent)

{

    svgWidget = new SvgWidget;

    setWidget (svgWidget);

}

/*

 * 将SVG文件加载到svgWidget中进行显示

 * 使svgWidget窗体按SVG图片的默认尺寸进行显示

*/

void SvgWindow::setFile (QString fileName)

{

    svgWidget->load (fileName);

    QSvgRenderer *render = svgWidget->renderer ();

    svgWidget->resize (render->defaultSize ());

}

/*

 * 当鼠标按下时mousePresspos和scrollBarValuesOnMousePress进行初始化

 * QScrollArea类的HorizontalScrollBar()和verticalScrollBar()函数

 * 可以分别获取svgWindow的水平滑动条和垂直滑动条

*/

void SvgWindow::mousePressEvent (QMouseEvent *event)

{

    mousePressPos = event->pos ();

    scrollBarValueOnMousePress.rx () = horizontalScrollBar ()->value ();

    scrollBarValueOnMousePress.ry () = verticalScrollBar ()->value ();

    event->accept ();

}

/*

 * 当鼠标键按下并拖曳鼠标时触发mouseMoveEvent()函数，通过滑动条的位置设置实现图片拖曳的效果

 * 对水平滑动条的新位置进行设置

 * 对垂直滑动条的新位置进行设置

*/

void SvgWindow::mouseMoveEvent (QMouseEvent *event)

{

    horizontalScrollBar()->setValue(scrollBarValueOnMousePress.x() - event->pos().x() + mousePressPos.x());

    verticalScrollBar()->setValue(scrollBarValueOnMousePress.y() - event->pos().y() + mousePressPos.y());

    horizontalScrollBar()->update();

    verticalScrollBar()->update();

    event->accept();

}

mainwindow.h

#ifndef MAINWINDOW_H

#define MAINWINDOW_H

/*

 * MainWindow继承自QMainWindow类，实现主窗口区域

*/

#include <QMainWindow>

#include "svgwindow.h"

class MainWindow : public QMainWindow

{

    Q_OBJECT

public:

    MainWindow(QWidget *parent = 0);

    ~MainWindow();

    void createMenu();

public slots:

    void slotOpenFile();

private:

    SvgWindow *svgWindow;   //以便调用相关函数传递选择的文件名

};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"

MainWindow::MainWindow(QWidget *parent)

    : QMainWindow(parent)

{

    setWindowTitle(tr("SVG Viewer"));

    this->resize (600, 400);

    createMenu();

    svgWindow =new SvgWindow;

    setCentralWidget(svgWindow);

}

MainWindow::~MainWindow()

{

}

/*

 * 创建一个打开文件的菜单

*/

void MainWindow::createMenu()

{

    QMenu *fileMenu = menuBar()->addMenu(tr("文件"));

    QAction *openAct = new QAction(tr("打开"),this);

    connect(openAct,SIGNAL(triggered()),this,SLOT(slotOpenFile()));

    fileMenu->addAction(openAct);

}

void MainWindow::slotOpenFile()

{

    QString name = QFileDialog::getOpenFileName(this,"打开","/","svg files(*.svg)");

    svgWindow->setFile(name);

}