QT 类及其实现效果(6)--画图

基本图形
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://多边形
        p.drawPolygon(points,4);
        break;
    case Polyline://多边线
        p.drawPolyline(points,4);
        break;
    case Points:
        p.drawPoints(points,4);
        break;
    case Arc:
        p.drawArc(rect,startAngle,spanAngle);//startAngle,spanAngle都是1/16度为单位
        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;
    }
}

设置渐变
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);

         linearGradient.setSpread(mainWidget->spread);//渐变的铺展效果，
         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);

         radialGradient.setSpread(mainWidget->spread);
         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);//conicalGradientt先默认构建成QBrush,再作为QPainter函数参数
     } else if (style == Qt::TexturePattern) {
         area->setBrush(QBrush(QPixmap(":/images/cheese.jpg")));
     } else {
         area->setBrush(QBrush(Qt::green, style));
     } 
}

 

 

 

 

设置画笔
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));
}

利用QPainterPath画图
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);
p.drawPath(path);

QPainter::addRect()可以用如下方式实现
path.moveTo(0,0);
path.lineTo(200,0);
path.lineTo(200,100);
path.lineTo(0,100);
path.lineTo(0,0);