学习QT之QT绘图实例

一、绘图原理

绘图就跟我们画画一样，首先需要一个画板、一个笔、一个画刷。画板用于作画，笔用于描线，画刷用于填充颜色。所以我们在作画前需要先做好这些准备，这些的具体介绍请参考我的前一篇文章学习QT之绘图原理详解。

三、运行结果

注：以下为部分截图

四、具体代码

paintera.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 = 0);
    void setShape(Shape);
    void setPen(QPen);
    void setBrush(QBrush);
    void setFillRule(Qt::FillRule);
    void paintEvent(QPaintEvent *);

private:
    Shape shape;
    QPen pen;
    QBrush brush;
    Qt::FillRule fillRule;
};

#endif // PAINTAREA_H

paintera.cpp

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

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();
}

void PaintArea::paintEvent(QPaintEvent *)
{
    QPainter p(this);
    p.setPen(pen);
    p.setBrush(brush);
    QRect rect(50,100,300,200);
    static const QPoint points[4] =
    {
        QPoint(150,100),
        QPoint(300,150),
        QPoint(350,250),
        QPoint(100,300)
    };
    int startAngle = 30*16;
    int spanAngle = 120*16;
    QPainterPath path;
    path.addRect(150,150,100,100);
    path.moveTo(100,100);
    path.cubicTo(300,100,200,200,300,300);
    path.cubicTo(100,300,200,200,100,100);
    path.setFillRule(fillRule);
    switch (shape) {
    case Line:
        p.drawLine(rect.topLeft(),rect.bottomRight());
        break;
    case Rectangle:
        p.drawRect(rect);
        break;
    case RoundRect:
        p.drawRoundRect(rect);
        break;
    case Ellipse:
        p.drawEllipse(rect);
        break;
    case Polygon:
        p.drawPolygon(points,4);
        break;
    case Polyline:
        p.drawPolyline(points,4);
        break;
    case Points:
        p.drawPoints(points,4);
        break;
    case Arc:
        p.drawArc(rect,startAngle,spanAngle);
        break;
    case Path:
        p.drawPath(path);
        break;
    case Text:
        p.drawText(rect,Qt::AlignCenter,tr("Hello Qt!"));
        break;
    case Pixmap:
        p.drawPixmap(150,150,QPixmap("321.png"));
        break;
    default:
        break;
    }
}

注：以上这个类是继承至QWidget，是我这个实例的画板

mainwidget.h

#ifndef MAINWIDGET_H
#define MAINWIDGET_H

#include <QWidget>
#include "paintarea.h"
#include <QLabel>
#include <QComboBox>
#include <QSpinBox>
#include <QPushButton>
#include <QGridLayout>
#include <QGradient>

class MainWidget : public QWidget
{
    Q_OBJECT

public:
    MainWidget(QWidget *parent = 0);
    ~MainWidget();

private:
    PaintArea *paintArea;
    QLabel *shapeLabel;
    QComboBox *shapeComboBox;
    QLabel *penWidthLabel;
    QSpinBox *penWidthSpinBox;
    QLabel *penColorLabel;
    QFrame *penColorFrame;
    QPushButton *penColorBtn;
    QLabel *penStyleLabel;
    QComboBox *penStyleComboBox;
    QLabel *penCapLabel;
    QComboBox *penCapComboBox;
    QLabel *penJoinLabel;
    QComboBox *penJoinComboBox;
    QLabel *fillRuleLabel;
    QComboBox *fillRuleComboBox;
    QLabel *spreadLabel;
    QComboBox *spreadComboBox;
    QGradient::Spread spread;
    QLabel *brushStyleLabel;
    QComboBox *brushStyleComboBox;
    QLabel *brushColorLabel;
    QFrame *brushColorFrame;
    QPushButton *brushColorBtn;
    QGridLayout *rightLayout;

protected slots:
    void showShape(int);
    void showPenWidth(int);
    void showPenColor();
    void showPenStyle(int);
    void showPenCap(int);
    void showPenJoin(int);
    void showSpreadStyle();
    void showFillRule();
    void showBrushColor();
    void showBrush(int);

};

#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)));
    penColorLabel = new QLabel(tr("画笔颜色"));
    penColorFrame = new QFrame;
    penColorFrame->setFrameStyle(QFrame::Panel | QFrame::Sunken);
    penColorFrame->setAutoFillBackground(true);
    penColorFrame->setPalette(QPalette(Qt::blue));
    penColorBtn = new QPushButton(tr("更改"));
    connect(penColorBtn,SIGNAL(clicked(bool)),this,SLOT(showPenColor()));
    penWidthLabel = new QLabel(tr("画笔线宽"));
    penWidthSpinBox = new QSpinBox;
    penWidthSpinBox->setRange(0,20);
    connect(penWidthSpinBox,SIGNAL(valueChanged(int)),this,SLOT(showPenWidth(int)));
    penStyleLabel = new QLabel(tr("画笔风格"));
    penStyleComboBox = new QComboBox;
    penStyleComboBox->addItem(tr("SolodLine"),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)));
    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)));
    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)));
    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()));
    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()));
    brushColorLabel = new QLabel(tr("画刷颜色"));
    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(bool)),this,SLOT(showBrushColor()));
    brushStyleLabel = new QLabel(tr("画刷风格"));
    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(showBrush(int)));
    rightLayout = new QGridLayout;
    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);
    mainLayout->addWidget(paintArea);
    mainLayout->addLayout(rightLayout);
    mainLayout->setStretchFactor(paintArea,1);
    mainLayout->setStretchFactor(rightLayout,0);
    showShape(shapeComboBox->currentIndex());
}

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));
    showBrush(brushStyleComboBox->currentIndex());
}

void MainWidget::showBrush(int value)
{
    //获得画刷的颜色
    QColor color = brushColorFrame->palette().color(QPalette::Window);
    Qt::BrushStyle style = Qt::BrushStyle(brushStyleComboBox->itemData(value,Qt::UserRole).toInt());
    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);
    }
    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);
    }
    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);
    }
    else if(style == Qt::TexturePattern)
    {
        paintArea->setBrush(QBrush(QPixmap("321.png")));
    }
    else
    {
        paintArea->setBrush(QBrush(color,style));
    }
}