利用QPainter绘制各种图形

利用QPainter绘制各种图形

Qt的二维图形引擎是基于QPainter类的。QPainter既可以绘制几何形状（点、线、矩形、椭圆、弧形、弦形、饼状图、多边形和贝塞尔曲线），也可以绘制像素映射、图像和文字。此外，QPainter还支持一些高级特性，例如反走样（针对文字和图形边缘）、像素混合、渐变填充和矢量路径等。QPainter也支持线性变换，例如平移、旋转、错切和缩放。

本例子中利用QPainter类提供的各种draw函数，绘制各种类型的图形，包括对图形的形状、颜色、填充风格等的选择。

1、创建paintarea.h

#ifndef PAINTAREA_H
#define PAINTAREA_H

#include <QtGui>

class PaintArea : public QWidget
{
Q_OBJECT

public:
enum Shape {Line,Rectangle,RoundRect,Ellipse,Polygon,Polyline,Points,Arc,Path,Text,Pixmap};
PaintArea(QWidget *parent = 0);

void setShape(Shape);
void setPen(QPen);
void setBrush(QBrush);

void paintEvent(QPaintEvent *);

private:
Shape shape;
QBrush brush;
QPen pen;
};
#endif // PAINTAREA_H

2、创建paintarea.cpp文件

#include "paintarea.h"

PaintArea::PaintArea(QWidget *parent) : QWidget(parent)
{
shape = Line;
QPalette p = palette();
p.setColor(QPalette::Window,Qt::white);
setPalette(p);
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::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);

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(":/images/butterfly.png"));
break;
default:
break;
}
}

3、创建mainwidget.h

#ifndef MAINWIDGET_H
#define MAINWIDGET_H

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

class MainWidget : public QWidget
{
Q_OBJECT

public:
MainWidget(QWidget *parent = 0);

public slots:
void slotShape(int);
void slotPenWidth(int);
void slotPenColor();
void slotPenStyle(int);
void slotPenCap(int);
void slotPenJoin(int);
void slotBrush(int);

private:
PaintArea *area;

QComboBox *shapeComboBox;
QSpinBox *widthSpinBox;
QComboBox *penStyleComboBox;
QComboBox *penCapComboBox;
QComboBox *penJoinComboBox;
QComboBox *brushStyleComboBox;
QFrame *colorFrame;
};

#endif // MAINWIDGET_H

4、创建mainwidget.cpp

#include "mainwidget.h"

MainWidget::MainWidget(QWidget *parent) : QWidget(parent)
{
area = new PaintArea;

QLabel *label1 = new QLabel(tr("Shape:"));
QLabel *label2 = new QLabel(tr("Pen Width:"));
QLabel *label3 = new QLabel(tr("Pen Color:"));
QLabel *label4 = new QLabel(tr("Pen Style:"));
QLabel *label5 = new QLabel(tr("Pen Cap:"));
QLabel *label6 = new QLabel(tr("Pen Join:"));
QLabel *label7 = new QLabel(tr("Brush:"));

shapeComboBox = new QComboBox;
shapeComboBox->addItem(tr("Line"), PaintArea::Line);
shapeComboBox->addItem(tr("Polygon"), PaintArea::Polygon);
shapeComboBox->addItem(tr("Rectangle"), PaintArea::Rectangle);
shapeComboBox->addItem(tr("Round Rectangle"), PaintArea::RoundRect);
shapeComboBox->addItem(tr("Ellipse"), PaintArea::Ellipse);
shapeComboBox->addItem(tr("Path"), PaintArea::Path);
shapeComboBox->addItem(tr("Polyline"), PaintArea::Polyline);
shapeComboBox->addItem(tr("Arc"), PaintArea::Arc);
shapeComboBox->addItem(tr("Points"), PaintArea::Points);
shapeComboBox->addItem(tr("Text"), PaintArea::Text);
shapeComboBox->addItem(tr("Pixmap"), PaintArea::Pixmap);
connect(shapeComboBox,SIGNAL(activated(int)),this,SLOT(slotShape(int)));

widthSpinBox = new QSpinBox;
widthSpinBox->setRange(0,20);
connect(widthSpinBox,SIGNAL(valueChanged(int)),this,SLOT(slotPenWidth(int)));

colorFrame = new QFrame;
colorFrame->setAutoFillBackground(true);
colorFrame->setPalette(QPalette(Qt::blue));
QPushButton *colorPushButton = new QPushButton(tr("change"));
connect(colorPushButton,SIGNAL(clicked()),this,SLOT(slotPenColor()));

penStyleComboBox = new QComboBox;
penStyleComboBox->addItem(tr("Solid"), Qt::SolidLine);
penStyleComboBox->addItem(tr("Dash"), Qt::DashLine);
penStyleComboBox->addItem(tr("Dot"), Qt::DotLine);
penStyleComboBox->addItem(tr("Dash Dot"), Qt::DashDotLine);
penStyleComboBox->addItem(tr("Dash Dot Dot"), Qt::DashDotDotLine);
penStyleComboBox->addItem(tr("None"), Qt::NoPen);
connect(penStyleComboBox,SIGNAL(activated(int)),this,SLOT(slotPenStyle(int)));

penCapComboBox = new QComboBox;
penCapComboBox->addItem(tr("Flat"), Qt::FlatCap);
penCapComboBox->addItem(tr("Square"), Qt::SquareCap);
penCapComboBox->addItem(tr("Round"), Qt::RoundCap);
connect(penCapComboBox,SIGNAL(activated(int)),this,SLOT(slotPenCap(int)));

penJoinComboBox = new QComboBox;
penJoinComboBox->addItem(tr("Miter"), Qt::MiterJoin);
penJoinComboBox->addItem(tr("Bevel"), Qt::BevelJoin);
penJoinComboBox->addItem(tr("Round"), Qt::RoundJoin);
connect(penJoinComboBox,SIGNAL(activated(int)),this,SLOT(slotPenJoin(int)));

brushStyleComboBox = new QComboBox;
brushStyleComboBox->addItem(tr("Linear Gradient"),
Qt::LinearGradientPattern);
brushStyleComboBox->addItem(tr("Radial Gradient"),
Qt::RadialGradientPattern);
brushStyleComboBox->addItem(tr("Conical Gradient"),
Qt::ConicalGradientPattern);
brushStyleComboBox->addItem(tr("Texture"), Qt::TexturePattern);
brushStyleComboBox->addItem(tr("Solid"), Qt::SolidPattern);
brushStyleComboBox->addItem(tr("Horizontal"), Qt::HorPattern);
brushStyleComboBox->addItem(tr("Vertical"), Qt::VerPattern);
brushStyleComboBox->addItem(tr("Cross"), Qt::CrossPattern);
brushStyleComboBox->addItem(tr("Backward Diagonal"), Qt::BDiagPattern);
brushStyleComboBox->addItem(tr("Forward Diagonal"), Qt::FDiagPattern);
brushStyleComboBox->addItem(tr("Diagonal Cross"), Qt::DiagCrossPattern);
brushStyleComboBox->addItem(tr("Dense 1"), Qt::Dense1Pattern);
brushStyleComboBox->addItem(tr("Dense 2"), Qt::Dense2Pattern);
brushStyleComboBox->addItem(tr("Dense 3"), Qt::Dense3Pattern);
brushStyleComboBox->addItem(tr("Dense 4"), Qt::Dense4Pattern);
brushStyleComboBox->addItem(tr("Dense 5"), Qt::Dense5Pattern);
brushStyleComboBox->addItem(tr("Dense 6"), Qt::Dense6Pattern);
brushStyleComboBox->addItem(tr("Dense 7"), Qt::Dense7Pattern);
brushStyleComboBox->addItem(tr("None"), Qt::NoBrush);
connect(brushStyleComboBox,SIGNAL(activated(int)),this,SLOT(slotBrush(int)));

QGridLayout *ctrlLayout = new QGridLayout;
int labelCol = 0;
int contentCol = 1;
ctrlLayout->addWidget(label1,0,labelCol);
ctrlLayout->addWidget(shapeComboBox,0,contentCol);
ctrlLayout->addWidget(label2,1,labelCol);
ctrlLayout->addWidget(widthSpinBox,1,contentCol);
ctrlLayout->addWidget(label3,2,labelCol);
ctrlLayout->addWidget(colorFrame,2,contentCol);
ctrlLayout->addWidget(colorPushButton,2,2);
ctrlLayout->addWidget(label4,3,labelCol);
ctrlLayout->addWidget(penStyleComboBox,3,contentCol);
ctrlLayout->addWidget(label5,4,labelCol);
ctrlLayout->addWidget(penCapComboBox,4,contentCol);
ctrlLayout->addWidget(label6,5,labelCol);
ctrlLayout->addWidget(penJoinComboBox,5,contentCol);
ctrlLayout->addWidget(label7,6,labelCol);
ctrlLayout->addWidget(brushStyleComboBox,6,contentCol);

QHBoxLayout *mainLayout = new QHBoxLayout;
mainLayout->addWidget(area);
mainLayout->addLayout(ctrlLayout);
mainLayout->setMargin(10);
mainLayout->setSpacing(10);

setLayout(mainLayout);

slotShape(0);
slotPenWidth(0);
slotPenStyle(0);
slotPenCap(0);
slotPenJoin(0);
slotBrush(0);
}

void MainWidget::slotShape(int value)
{
PaintArea::Shape shape = PaintArea::Shape(shapeComboBox->itemData(value,Qt::UserRole).toInt());
area->setShape(shape);
}

void MainWidget::slotPenWidth(int value)
{
QColor color = colorFrame->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());

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

void MainWidget::slotPenColor()
{
QColor color = QColorDialog::getColor(Qt::blue);

colorFrame->setPalette(QPalette(color));

int width = widthSpinBox->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());

area->setPen(QPen(color, width, style, cap, join));
}

void MainWidget::slotPenStyle(int value)
{
int width = widthSpinBox->value();
QColor color = colorFrame->palette().color(QPalette::Window);
Qt::PenStyle style = Qt::PenStyle(penStyleComboBox->itemData(value,  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());

area->setPen(QPen(color, width, style, cap, join));
}

void MainWidget::slotPenCap(int value)
{
int width = widthSpinBox->value();
QColor color = colorFrame->palette().color(QPalette::Window);
Qt::PenStyle style = Qt::PenStyle(penStyleComboBox->itemData(
penStyleComboBox->currentIndex(),  Qt::UserRole).toInt());
Qt::PenCapStyle cap = Qt::PenCapStyle(penCapComboBox->itemData(value,  Qt::UserRole).toInt());
Qt::PenJoinStyle join = Qt::PenJoinStyle(penJoinComboBox->itemData(
penJoinComboBox->currentIndex(),  Qt::UserRole).toInt());

area->setPen(QPen(color, width, style, cap, join));
}

void MainWidget::slotPenJoin(int value)
{
int width = widthSpinBox->value();
QColor color = colorFrame->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(value,  Qt::UserRole).toInt());

area->setPen(QPen(color, width, style, cap, join));
}

void MainWidget::slotBrush(int value)
{
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, Qt::green);
linearGradient.setColorAt(1.0, Qt::black);
area->setBrush(linearGradient);
} else if (style == Qt::RadialGradientPattern) {
QRadialGradient radialGradient(200, 200, 150, 150, 100);
radialGradient.setColorAt(0.0, Qt::white);
radialGradient.setColorAt(0.2, Qt::green);
radialGradient.setColorAt(1.0, Qt::black);
area->setBrush(radialGradient);
} else if (style == Qt::ConicalGradientPattern) {
QConicalGradient conicalGradient(200, 200, 30);
conicalGradient.setColorAt(0.0, Qt::white);
conicalGradient.setColorAt(0.2, Qt::green);
conicalGradient.setColorAt(1.0, Qt::black);
area->setBrush(conicalGradient);
} else if (style == Qt::TexturePattern) {
area->setBrush(QBrush(QPixmap(":/images/cheese.jpg")));
} else {
area->setBrush(QBrush(Qt::green, style));
}
}

5、创建资源文件paintbasic.qrc

6、创建main.cpp

#include <QApplication>
#include "mainwidget.h"

int main(int argc, char * argv[])
{
QApplication app(argc,argv);

MainWidget w;
w.show();

return app.exec();
}

6、编译运行



7、资源代码文件