基本图形绘制

QPainter绘制基本图形

**注意：**QPainter画弧度所使用的角度值，是以1/16°为单位的，在画弧度的时候1°用16表示。

**例如：**30°——30 x 16

兼容模式QPainer::CompositionMode

**例如:**可用于图片叠加，达到你想要的效果。

---

QPainterPath绘制简单图形

QPainterPath为QPainter类提供一个存储容器，里面包含了所要绘制的内容的集合及绘制顺序，如长方形、多边形、曲线等各种任意图形。当需要绘制此预先存储在QPainterPath对象中的内容时，只需调用QPainter类的DrawPath()即可，如addRect()加入一个方形，addEllipse加入一个椭圆形，addText()加入文本。

---

画笔笔刷风格

画笔风格——Qt::PenStyle

笔帽风格——Qt::PenCapStyle

Qt::SquareCap 方形线端，不覆盖线的端点

Qt::FlatCap 方形线端，覆盖线的端点，并以线框一半向外延伸

Qt::RoundCap 圆线端

连接点——Qt::PenJoinStyle

Qt::BevelJoin 两条线相汇形成方形连接

Qt::MiterJoin 两条线相汇形成尖角连接

Qt::RoundJoin两条线相汇形成圆角连接

填充模式——Qt::FillRule

• Qt::OddEventFill填充规则：从图形中某一点画一条水平线到图形外，若这条线与图形边线的交点为奇数则说明此点位与图形的内部；若交点为偶数则此点在图形的外部。
• Qt::WindingFill填充规则：从图形中某一点画一条水平线到图形外，每个交点外边线方向可能向上、向下、方向相反的相互抵消，若结果不为0表示此点在图形内，若为0则在图形外。其中边线的方向是由QPainterPath创建时根据描述的顺序决定的，如果采用addRect()或addPolygon()等函数加入的图形默认为顺时针方向。

铺展效果——Qt::Gradient::Type

QGradient::PadSpread :默认风格

QGradient::RepeatSpread:线性渐变

QGradient::ReflectSpread:圆形渐变

画刷风格——Qt::BrushStyle

---

示例

mainwidget.h

#ifndef MAINWIDGET_H
#define MAINWIDGET_H

#include <QWidget>
#include<paintarea.h>
#include<QLabel>
#include<QComboBox>
#include<QSpinBox>
#include<QPushButton>
#include<QGridLayout>
class MainWidget : public QWidget
{
    Q_OBJECT

public:
    MainWidget(QWidget *parent = 0);
    ~MainWidget();
    void   initWidgets();
private slots:
    void  ShowShape(int value);
    void ShowPenColor();
    void ShowPenWidth(int value);
    void ShowPenStyle(int value);
    void ShowPenCap(int value);
    void ShowPenJoin(int value);
    void ShowFillRule(int value);
    void ShowSpreadStyle(int value);
    void ShowBrushColor();
    void ShowBrush(int value);
private:
    PaintArea* m_paintArea; //绘图区域
    QLabel* m_shapeLabel ; //形状
    QComboBox* m_shapeCombox;
    QLabel* m_penWidthLabel;//线宽
    QSpinBox *m_penWithSpinBox;
    QLabel* m_penColorLabel;//画笔颜色
    QFrame* m_penColorFrame;
    QPushButton* m_penColorBtn;//确认选择画笔颜色按钮
    QLabel* m_penStyleLabel;//画笔风格
    QComboBox* m_penStyleComboBox;
    QLabel* m_penCapLabel;//笔帽风格
    QComboBox* m_penCapComboBox;
    QLabel* m_penJoinLabel;//画笔连接点
    QComboBox* m_penJoinComboBox;
    QLabel* m_fillRuleLabel;//填充模式
    QComboBox* m_fillRuleComboBox;
    QLabel* m_spreadLabel;//铺展效果
    QComboBox* m_spreadComboBox;
    QGradient::Spread m_spread;
    QLabel* m_brushColorLabel;//画刷颜色
    QFrame* m_brushColorFrame;
    QPushButton* m_brushColorBtn;
    QLabel* m_brushStyleLabel;//画刷风格
    QComboBox* m_brushStytleComboBox;
    QGridLayout* m_rightLayout;

};

#endif // MAINWIDGET_H

mainwidget.cpp

#include "mainwidget.h"
#include<QColorDialog>
MainWidget::MainWidget(QWidget *parent)
    : QWidget(parent)
{
    initWidgets();
}

MainWidget::~MainWidget()
{

}

//初始化部件
void MainWidget::initWidgets()
{
    m_paintArea = new PaintArea;
    m_shapeLabel = new QLabel(tr("形状"));
    m_shapeCombox = new QComboBox;

    m_shapeCombox->addItem(tr("Line"),PaintArea::Line);
    m_shapeCombox->addItem(tr("Rectangle"),PaintArea::Rectangle);
    m_shapeCombox->addItem(tr("RoundedRect"),PaintArea::Rectangle);
    m_shapeCombox->addItem(tr("Ellipse"),PaintArea::Ellipse);
    m_shapeCombox->addItem(tr("Polygon"),PaintArea::Polygon);
    m_shapeCombox->addItem(tr("Polyline"),PaintArea::Polyline);
    m_shapeCombox->addItem(tr("Points"),PaintArea::Points);
    m_shapeCombox->addItem(tr("Arc"),PaintArea::Arc);
    m_shapeCombox->addItem(tr("Path"),PaintArea::Path);
    m_shapeCombox->addItem(tr("Text"),PaintArea::Text);
    m_shapeCombox->addItem(tr("Pixmap"),PaintArea::Pixmap);
    connect(m_shapeCombox,SIGNAL(activated(int)),this,SLOT(ShowShape(int)));

    m_penColorLabel = new QLabel(tr("画笔颜色"));
    m_penColorFrame = new QFrame;
    m_penColorFrame->setFrameStyle(QFrame::Panel | QFrame::Sunken);//设置风格
    m_penColorFrame->setAutoFillBackground(true);
    m_penColorFrame->setPalette(QPalette(Qt::black));
    m_penColorBtn = new QPushButton(tr("更改"));
    connect(m_penColorBtn,SIGNAL(clicked(bool)),this,SLOT(ShowPenColor()));

    m_penWidthLabel = new QLabel(tr("画线宽度"));
    m_penWithSpinBox = new QSpinBox;
    m_penWithSpinBox->setRange(1,20);
    connect(m_penWithSpinBox,SIGNAL( valueChanged(int)),SLOT(ShowPenWidth(int)));

    m_penStyleLabel = new QLabel(tr("画笔风格"));
    m_penStyleComboBox  = new QComboBox;
    m_penStyleComboBox->addItem(tr("SolidLine"),static_cast<int>(Qt::SolidLine ));
    m_penStyleComboBox->addItem(tr("DashLine"),static_cast<int>(Qt::DashLine));
    m_penStyleComboBox->addItem(tr("DotLine"),static_cast<int>(Qt::DotLine));
    m_penStyleComboBox->addItem(tr("DashDotLine"),static_cast<int>(Qt::DashDotLine ));
    m_penStyleComboBox->addItem(tr("DashDotDotLine"),static_cast<int>(Qt::DashDotDotLine ));
    m_penStyleComboBox->addItem(tr("CustomDashLine"),static_cast<int>(Qt::CustomDashLine));
    connect(m_penStyleComboBox,SIGNAL(activated(int)),this,SLOT(ShowPenStyle(int)));

    m_penCapLabel = new QLabel(tr("画笔笔帽"));
    m_penCapComboBox = new QComboBox;
    m_penCapComboBox->addItem(tr("SquareCap"),Qt::SquareCap);
    m_penCapComboBox->addItem(tr("FlatCap"),Qt::FlatCap);
    m_penCapComboBox->addItem(tr("RoundCap"),Qt::RoundCap);
    connect(m_penCapComboBox,SIGNAL(activated(int)),this,SLOT(ShowPenCap(int)));

    m_penJoinLabel = new QLabel(tr("画笔连接点"));
    m_penJoinComboBox = new QComboBox;
    m_penJoinComboBox->addItem(tr("BevelJoin"),Qt::BevelJoin);
    m_penJoinComboBox->addItem(tr("MiterJoin"),Qt::MiterJoin);
    m_penJoinComboBox->addItem(tr("RoundJoin"),Qt::RoundJoin);
    connect(m_penJoinComboBox,SIGNAL(activated(int)),this,SLOT(ShowPenJoin(int)));

    m_fillRuleLabel = new QLabel(tr("填充模式"));
    m_fillRuleComboBox = new QComboBox;
    m_fillRuleComboBox->addItem(tr("Odd Even"),Qt::OddEvenFill);
    m_fillRuleComboBox->addItem(tr("Winding"),Qt::WindingFill);
    connect(m_fillRuleComboBox,SIGNAL(activated(int)),this,SLOT(ShowFillRule(int)));

    m_spreadLabel = new QLabel(tr("铺展效果"));
    m_spreadComboBox = new QComboBox;
    m_spreadComboBox->addItem(tr("PadStread"),QGradient::PadSpread);
    m_spreadComboBox->addItem(tr("RepeatSpread"),QGradient::RepeatSpread);
    m_spreadComboBox->addItem(tr("ReflectSpread"),QGradient::ReflectSpread);
    connect(m_spreadComboBox,SIGNAL(activated(int)),this,SLOT(ShowSpreadStyle(int)));

    m_brushColorLabel = new QLabel(tr("画刷颜色"));
    m_brushColorFrame = new QFrame;
    m_brushColorFrame->setFrameStyle(QFrame::Panel | QFrame::Sunken);
    m_brushColorFrame->setAutoFillBackground(true);
    m_brushColorFrame->setPalette(QPalette(Qt::green));
    m_brushColorBtn = new QPushButton(tr("更改"));
    connect(m_brushColorBtn,SIGNAL(clicked()),this,SLOT(ShowBrushColor()) );

    m_brushStyleLabel = new QLabel(tr("画刷风格"));
    m_brushStytleComboBox = new QComboBox;
    m_brushStytleComboBox->addItem(tr("SolidPattern"),static_cast<int>(Qt::SolidPattern));
    m_brushStytleComboBox->addItem(tr("Dense1Pattern"),static_cast<int>(Qt::Dense1Pattern));
    m_brushStytleComboBox->addItem(tr("Dense2Pattern"),static_cast<int>(Qt::Dense2Pattern));
    m_brushStytleComboBox->addItem(tr("Dense3Pattern"),static_cast<int>(Qt::Dense3Pattern));
    m_brushStytleComboBox->addItem(tr("Dense4Pattern"),static_cast<int>(Qt::Dense4Pattern));
    m_brushStytleComboBox->addItem(tr("Dense5Pattern"),static_cast<int>(Qt::Dense5Pattern));
    m_brushStytleComboBox->addItem(tr("Dense6Pattern"),static_cast<int>(Qt::Dense6Pattern));
    m_brushStytleComboBox->addItem(tr("Dense7Pattern"),static_cast<int>(Qt::Dense7Pattern));
    m_brushStytleComboBox->addItem(tr("HorPattern"),static_cast<int>(Qt::HorPattern));
    m_brushStytleComboBox->addItem(tr("VerPattern"),static_cast<int>(Qt::VerPattern));
    m_brushStytleComboBox->addItem(tr("CrossPattern"),static_cast<int>(Qt::CrossPattern));
    m_brushStytleComboBox->addItem(tr("BDiagPattern"),static_cast<int>(Qt::BDiagPattern));
    m_brushStytleComboBox->addItem(tr("FDiagPattern"),static_cast<int>(Qt::FDiagPattern));
    m_brushStytleComboBox->addItem(tr("DiagCrossPattern"),static_cast<int>(Qt::DiagCrossPattern));
    m_brushStytleComboBox->addItem(tr("LinearGradientPattern"),static_cast<int>(Qt::LinearGradientPattern));
    m_brushStytleComboBox->addItem(tr("ConicalGradientPattern"),static_cast<int>(Qt::ConicalGradientPattern));
    m_brushStytleComboBox->addItem(tr("RadialGradientPattern"),static_cast<int>(Qt::RadialGradientPattern));
    m_brushStytleComboBox->addItem(tr("TexturePattern"),static_cast<int>(Qt::TexturePattern));
    connect(m_brushStytleComboBox,SIGNAL(activated(int)),this,SLOT(ShowBrush(int)));

    //添加布局
    m_rightLayout = new QGridLayout;
    m_rightLayout->addWidget(m_shapeLabel,0,0);
    m_rightLayout->addWidget(m_shapeCombox,0,1);
    m_rightLayout->addWidget(m_penColorLabel,1,0);
    m_rightLayout->addWidget(m_penColorFrame,1,1);
    m_rightLayout->addWidget(m_penColorBtn,1,2);
    m_rightLayout->addWidget(m_penWidthLabel,2,0);
    m_rightLayout->addWidget(m_penWithSpinBox,2,1);
    m_rightLayout->addWidget(m_penStyleLabel,3,0);
    m_rightLayout->addWidget(m_penStyleComboBox,3,1);
    m_rightLayout->addWidget(m_penCapLabel,4,0);
    m_rightLayout->addWidget(m_penCapComboBox,4,1);
    m_rightLayout->addWidget(m_penJoinLabel,5,0);
    m_rightLayout->addWidget(m_penJoinComboBox,5,1);
    m_rightLayout->addWidget(m_fillRuleLabel,6,0);
    m_rightLayout->addWidget(m_fillRuleComboBox,6,1);
    m_rightLayout->addWidget(m_spreadLabel,7,0);
    m_rightLayout->addWidget(m_spreadComboBox,7,1);
    m_rightLayout->addWidget(m_brushColorLabel,8,0);
    m_rightLayout->addWidget(m_brushColorFrame,8,1);
    m_rightLayout->addWidget(m_brushColorBtn,8,2);
    m_rightLayout->addWidget(m_brushStyleLabel,9,0);
    m_rightLayout->addWidget(m_brushStytleComboBox,9,1);

    QHBoxLayout* mainLayout = new QHBoxLayout(this);
    mainLayout->addWidget(m_paintArea);
    mainLayout->addLayout(m_rightLayout);
    ShowShape(m_shapeCombox->currentIndex());

}

//变更每项设置后，更新图像

void MainWidget::ShowShape(int value)
{
    PaintArea::Shape shape =PaintArea::Shape (m_shapeCombox->itemData(value).toInt());//获取用户选择的形状
    m_paintArea->setShape(shape);
}

void MainWidget::ShowPenColor()
{
    QColor color = QColorDialog::getColor(Qt::black);
    m_penColorFrame->setPalette(QPalette(color));
    int value = m_penWithSpinBox->value();

    int styleIndex = m_penStyleComboBox->currentIndex();
    Qt::PenStyle style = Qt::PenStyle(m_penStyleComboBox->itemData(styleIndex).toInt());

    int capIndex = m_penCapComboBox->currentIndex();
    Qt::PenCapStyle cap = Qt::PenCapStyle(m_penCapComboBox->itemData(capIndex).toInt());

    int joinIndex = m_penJoinComboBox->currentIndex();
    Qt::PenJoinStyle join = Qt::PenJoinStyle(m_penJoinComboBox->itemData(joinIndex).toInt());

    //将当前画笔的各个参数传递-设置
    m_paintArea->setPen(QPen(color,value,style,cap,join));
}

void MainWidget::ShowPenWidth(int value)
{
    QColor color = m_penColorFrame->palette().color(QPalette::Window);//获取颜色框中关于窗体的颜色值
    m_penColorFrame->setPalette(QPalette(color));
    int penWidth =value;

    int styleIndex = m_penStyleComboBox->currentIndex();
    Qt::PenStyle style = Qt::PenStyle(m_penStyleComboBox->itemData(styleIndex).toInt());

    int capIndex = m_penCapComboBox->currentIndex();
    Qt::PenCapStyle cap = Qt::PenCapStyle(m_penCapComboBox->itemData(capIndex).toInt());

    int joinIndex = m_penJoinComboBox->currentIndex();
    Qt::PenJoinStyle join = Qt::PenJoinStyle(m_penJoinComboBox->itemData(joinIndex).toInt());

    //将当前画笔的各个参数传递-设置
    m_paintArea->setPen(QPen(color,penWidth,style,cap,join));
}

void MainWidget::ShowPenStyle(int value)
{
    QColor color = m_penColorFrame->palette().color(QPalette::Window);//获取颜色框中关于窗体的颜色值
    m_penColorFrame->setPalette(QPalette(color));
    int penWidth = m_penWithSpinBox->value();


    Qt::PenStyle style = Qt::PenStyle(m_penStyleComboBox->itemData(value).toInt());
     if(style == Qt::CustomDashLine)//如果是自定义的
     {
         QVector<qreal> dashes;
         qreal space = 4;
         dashes<<1<<space<<2<<space<<3<<space<<4<<space;
         m_paintArea->m_pen.setDashPattern(dashes);
         m_paintArea->update();
     }
     else
     {
         int capIndex = m_penCapComboBox->currentIndex();
         Qt::PenCapStyle cap = Qt::PenCapStyle(m_penCapComboBox->itemData(capIndex).toInt());

         int joinIndex = m_penJoinComboBox->currentIndex();
         Qt::PenJoinStyle join = Qt::PenJoinStyle(m_penJoinComboBox->itemData(joinIndex).toInt());

         //将当前画笔的各个参数传递-设置
         m_paintArea->setPen(QPen(color,penWidth,style,cap,join));
     }
}

void MainWidget::ShowPenCap(int value)
{
    QColor color = m_penColorFrame->palette().color(QPalette::Window);//获取颜色框中关于窗体的颜色值
    m_penColorFrame->setPalette(QPalette(color));
    int penWidth =m_penWithSpinBox->value();

    int styleIndex = m_penStyleComboBox->currentIndex();
    Qt::PenStyle style = Qt::PenStyle(m_penStyleComboBox->itemData(styleIndex).toInt());

   // int capIndex = m_penCapComboBox->currentIndex();
    Qt::PenCapStyle cap = Qt::PenCapStyle(m_penCapComboBox->itemData(value).toInt());

    int joinIndex = m_penJoinComboBox->currentIndex();
    Qt::PenJoinStyle join = Qt::PenJoinStyle(m_penJoinComboBox->itemData(joinIndex).toInt());

    //将当前画笔的各个参数传递-设置
    m_paintArea->setPen(QPen(color,penWidth,style,cap,join));
}

void MainWidget::ShowPenJoin(int value)
{
    QColor color = m_penColorFrame->palette().color(QPalette::Window);//获取颜色框中关于窗体的颜色值
    m_penColorFrame->setPalette(QPalette(color));
    int penWidth =m_penWithSpinBox->value();

    int styleIndex = m_penStyleComboBox->currentIndex();
    Qt::PenStyle style = Qt::PenStyle(m_penStyleComboBox->itemData(styleIndex).toInt());

    int capIndex = m_penCapComboBox->currentIndex();
    Qt::PenCapStyle cap = Qt::PenCapStyle(m_penCapComboBox->itemData(capIndex).toInt());

   // int joinIndex = m_penJoinComboBox->currentIndex();
    Qt::PenJoinStyle join = Qt::PenJoinStyle(m_penJoinComboBox->itemData(value).toInt());

    //将当前画笔的各个参数传递-设置
    m_paintArea->setPen(QPen(color,penWidth,style,cap,join));
}

void MainWidget::ShowFillRule(int value)
{
    Qt::FillRule rule = Qt::FillRule(value);
    m_paintArea->setFillRule(rule);
}

void MainWidget::ShowSpreadStyle(int value)
{
    m_spread = QGradient::Spread(value);
}

void MainWidget::ShowBrushColor()
{
    QColor color = QColorDialog::getColor(Qt::green);
    m_brushColorFrame->setPalette(QPalette(color));
    ShowBrush(m_brushStytleComboBox->currentIndex());
}

void MainWidget::ShowBrush(int value)
{
    QColor  color = m_brushColorFrame->palette().color(QPalette::Window);
    int brush = m_brushStytleComboBox->itemData(value).toInt();
    Qt::BrushStyle style = Qt::BrushStyle(brush);

    //线性渐变
    if(style == Qt::LinearGradientPattern)
    {
        //指定线性渐变的区域
      QLinearGradient lineGradient(0,0,400,400);
      //指定某个位置的渐变色，pos取值范围0~1
      lineGradient.setColorAt(0.0,Qt::white);
      lineGradient.setColorAt(0.2,color);
      lineGradient.setColorAt(1.0,Qt::black);
      lineGradient.setSpread(m_spread);

      m_paintArea->setBrush(lineGradient);
    }
    //环形渲染
    else if(style == Qt::RadialGradientPattern)
    {
        //中心坐标，半径长度,焦点坐标，如果需要对称，则中心坐标和焦点坐标保持一致
        QRadialGradient radiaGrdient(200,200,150,200,200);
      radiaGrdient.setColorAt(0.0,Qt::white);
      radiaGrdient.setColorAt(0.2,color);
      radiaGrdient.setColorAt(1.0,Qt::black);

      m_paintArea->setBrush(radiaGrdient);
    }
    //弧度渲染
    else if(style == Qt::ConicalGradientPattern)
    {
         //中心坐标，角度
         QConicalGradient conicaoGradient(200,200,30);
         conicaoGradient.setColorAt(0.0,Qt::white);
         conicaoGradient.setColorAt(0.2,color);
         conicaoGradient.setColorAt(1.0,Qt::black);

         m_paintArea->setBrush(conicaoGradient);
    }
    else if(style == Qt::TexturePattern)
    {
        m_paintArea->setBrush(QBrush(QPixmap("test1.jpg")));
    }
    //其他
    else
    {
        m_paintArea->setBrush(QBrush(color,style));
    }
}

paintarea.h

#ifndef PAINTAREA_H
#define PAINTAREA_H

#include <QWidget>
#include<QPen>
#include<QBrush>

class PaintArea : public QWidget
{
    Q_OBJECT
public:
    enum Shape{Line,Rectangle,RoundRect,Ellipse,Polygon,Polyline,Points,Arc,Path,Text,Pixmap};
    explicit PaintArea(QWidget *parent = nullptr);

public:
    void setShape(Shape shape);
    void setPen(QPen pen);
    void setBrush(QBrush brush);
    void setFillRule(Qt::FillRule rule);
protected:
     void paintEvent(QPaintEvent *event)override;
public:
     QPen m_pen;
private:
      Shape m_shape;

      QBrush m_brush;
      Qt::FillRule m_fillrule;


signals:

public slots:
};

#endif // PAINTAREA_H

paintarea.cpp

#include "paintarea.h"
#include<QPainter>

PaintArea::PaintArea(QWidget *parent) : QWidget(parent)
{
    setPalette(QPalette(Qt::white));
    setAutoFillBackground(true);//设置背景自动填充
    setFixedSize(400,400);


}

void PaintArea::setShape(PaintArea::Shape shape)
{
    m_shape = shape;
    update();
}

void PaintArea::setPen(QPen pen)
{
    m_pen = pen;
    update();
}

void PaintArea::setBrush(QBrush brush)
{
    m_brush = brush;
    update();
}

void PaintArea::setFillRule(Qt::FillRule rule)
{
    m_fillrule = rule;
    update();
}

void PaintArea::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    painter.setPen(m_pen);
    painter.setBrush(m_brush);
    QRect rect(50,100,300,200);//起始位置，宽高
    const QPoint points[4]= {
        QPoint(150,100),
        QPoint(300,150),
        QPoint(100,300),
        QPoint(100,300)
    };
    int startAngle = 30 * 16;//1/16
    int spanAngle = 120 * 16;
    QPainterPath path;
    path.addRect(150,150,100,100);
    path.moveTo(100,200);
    path.cubicTo(300,100,200,200,300,300);
    path.cubicTo(100,300,200,200,100,100);
    path.setFillRule(m_fillrule);

    switch(m_shape)
    {
    case Line:
        painter.drawLine(rect.topLeft(),rect.bottomRight());
        break;
    case Rectangle:
        painter.drawRect(rect);
        break;
    case RoundRect:
        painter.drawRoundRect(rect);
        break;
    case Ellipse:
        painter.drawEllipse(rect);
        break;
    case Polygon://多边形,默认为4变形
        painter.drawPolygon(points,4);
        break;
    case Polyline:
        painter.drawPolyline(points,4);
        break;
    case Points:
        painter.drawPoints(points,4);
        break;
    case Arc:
        painter.drawArc(rect, startAngle,spanAngle);
        break;
    case Path:
        painter.drawPath(path);
        break;
    case Text:
        painter.drawText(rect,Qt::AlignCenter,tr("Hello world!"));
        break;
    case Pixmap:
        painter.drawPixmap(50,100,QPixmap("test1.jpg"));
        break;
    default:
        break;
    }

}