Qt绘制各种图形
重载绘图事件：
protected:
void paintEvent(QPaintEvent *event) Q_DECL_OVERRIDE;
void Widget::paintEvent(QPaintEvent *event)
{
进行绘图操作
}绘图前操作：
//基本绘图
QPainter painter(this);//创建QPainter对象
painter.setRenderHint(QPainter::Antialiasing);//
painter.setRenderHint(QPainter::TextAntialiasing);//
int W=this->width(); //绘图区宽度
int H=this->height(); //绘图区高度
QRect rect(W/4,H/4,W/2,H/2); //中间区域矩形框
//设置画笔
QPen pen;
pen.setWidth(3); //线宽
pen.setColor(Qt::red); //划线颜色
//Qt::NoPen,Qt::SolidLine, Qt::DashLine, Qt::DotLine,Qt::DashDotLine,Qt::DashDotDotLine,Qt::CustomDashLine
pen.setStyle(Qt::SolidLine);//线的类型，实线、虚线等
//Qt::FlatCap, Qt::SquareCap,Qt::RoundCap
pen.setCapStyle(Qt::FlatCap);//线端点样式
//Qt::MiterJoin,Qt::BevelJoin,Qt::RoundJoin,Qt::SvgMiterJoin
pen.setJoinStyle(Qt::BevelJoin);//线的连接点样式
painter.setPen(pen);
//设置画刷
// QPixmap texturePixmap(":images/images/texture.jpg");
QBrush brush;
brush.setColor(Qt::yellow); //画刷颜色
brush.setStyle(Qt::SolidPattern); //画刷填充样式
// brush.setStyle(Qt::TexturePattern); //画刷填充样式
// brush.setTexture(texturePixmap); //设置材质图片
painter.setBrush(brush);绘图：
painter.drawLine(rect.left(),rect.top(),rect.right(),rect.bottom());
painter.drawRect(rect); //只填充定义的渐变区域
painter.drawRect(this->rect()); //填充更大区域，会有延展效果
painter.fillRect(rect,Qt::red);
painter.drawRoundRect(rect);
painter.drawRoundedRect(rect,40,20);
painter.drawEllipse(rect);
painter.drawPolyline(points,9);
painter.drawPolygon(points,9);
painter.drawPoints(points,9);
painter.translate(100,300);
painter.drawPath(starPath);
painter.translate(200,0);
painter.drawPath(starPath);
painter.translate(200,0);
painter.drawPath(starPath);
painter.drawArc(rect,30*16,80*16);
painter.drawChord(rect,90*16,120*16);
painter.drawPie(rect,90*16,120*16);
painter.drawText(rect,"Hello, QT");通用函数：
void Widget::myDrawTextureRect()
{
QPainter painter(this);//创建QPainter对象
painter.setRenderHint(QPainter::Antialiasing);//
painter.setRenderHint(QPainter::TextAntialiasing);//
int W=this->width(); //绘图区宽度
int H=this->height(); //绘图区高度
QRect rect(W/4,H/4,W/2,H/2); //中间区域矩形框
//设置画笔
QPen pen;
pen.setWidth(3); //线宽
pen.setColor(Qt::red); //划线颜色
//Qt::NoPen,Qt::SolidLine, Qt::DashLine, Qt::DotLine,Qt::DashDotLine,Qt::DashDotDotLine,Qt::CustomDashLine
pen.setStyle(Qt::SolidLine);//线的类型，实线、虚线等
//Qt::FlatCap, Qt::SquareCap,Qt::RoundCap
pen.setCapStyle(Qt::FlatCap);//线端点样式
//Qt::MiterJoin,Qt::BevelJoin,Qt::RoundJoin,Qt::SvgMiterJoin
pen.setJoinStyle(Qt::BevelJoin);//线的连接点样式
painter.setPen(pen);
//设置画刷
QPixmap texturePixmap(":images/images/texture.jpg");
QBrush brush;
// brush.setColor(Qt::yellow); //画刷颜色
// brush.setStyle(Qt::SolidPattern); //画刷填充样式
brush.setStyle(Qt::TexturePattern); //画刷填充样式
brush.setTexture(texturePixmap); //设置材质图片
painter.setBrush(brush);
//绘图
painter.drawRect(rect); //只填充定义的渐变区域
}绘制渐变色：
void Widget::myDrawGradient()
{
QPainter painter(this);//创建QPainter对象
painter.setRenderHint(QPainter::Antialiasing);//
painter.setRenderHint(QPainter::TextAntialiasing);//
int W=this->width(); //绘图区宽度
int H=this->height(); //绘图区高度
QRect rect(W/4,H/4,W/2,H/2); //中间区域矩形框
//设置画笔
// QPen pen;
// pen.setStyle(Qt::NoPen);//线的类型，实线、虚线等
// painter.setPen(pen);
//线性渐变
// QLinearGradient linearGrad(rect.left(),rect.top(),rect.right(),rect.bottom()); //对角线
QLinearGradient linearGrad(rect.left(),rect.top(),rect.right(),rect.top());//从左到右
linearGrad.setColorAt(0,Qt::blue);//起点颜色
linearGrad.setColorAt(0.5,Qt::green);//起点颜色
linearGrad.setColorAt(1,Qt::red);//终点颜色
linearGrad.setSpread(QGradient::ReflectSpread); //展布模式
//QGradient::PadSpread ,QGradient::RepeatSpread, QGradient::ReflectSpread
painter.setBrush(linearGrad);
//径向渐变
// QRadialGradient radialGrad(W/2,H/2,qMax(W/8,H/8),W/2,H/2);
radialGrad.setColorAt(0,Qt::white);
// radialGrad.setColorAt(0,Qt::green);
// radialGrad.setColorAt(1,Qt::blue);
// radialGrad.setSpread(QGradient::ReflectSpread);
// //QGradient::PadSpread ,QGradient::RepeatSpread, QGradient::ReflectSpread
// painter.setBrush(radialGrad);
//圆锥型渐变
// QConicalGradient coniGrad(W/2,H/2,45);
// coniGrad.setColorAt(0,Qt::yellow);
// coniGrad.setColorAt(0.5,Qt::blue);
// coniGrad.setColorAt(1,Qt::green);
coniGrad.setSpread(QGradient::PadSpread); //对于锥形渐变不起作用
// painter.setBrush(coniGrad);
//绘图
// painter.drawRect(rect); //只填充定义的渐变区域
painter.drawRect(this->rect()); //填充更大区域，会有延展效果
}绘制各种图形：
void Widget::myDrawShape()
{
QPainter painter(this);//创建QPainter对象
painter.setRenderHint(QPainter::Antialiasing);
painter.setRenderHint(QPainter::TextAntialiasing);
int W=this->width(); //绘图区宽度
int H=this->height(); //绘图区高度
//设置画笔
QPen pen;
pen.setWidth(3); //线宽
pen.setColor(Qt::black); //划线颜色
//Qt::NoPen,Qt::SolidLine, Qt::DashLine, Qt::DotLine,Qt::DashDotLine,Qt::DashDotDotLine,Qt::CustomDashLine
pen.setStyle(Qt::SolidLine);//线的类型，实线、虚线等
//Qt::FlatCap, Qt::SquareCap,Qt::RoundCap
pen.setCapStyle(Qt::FlatCap);//线端点样式
//Qt::MiterJoin,Qt::BevelJoin,Qt::RoundJoin,Qt::SvgMiterJoin
pen.setJoinStyle(Qt::BevelJoin);//线的连接点样式
painter.setPen(pen);
//1. drawArc()
// QRect rect(W/4,H/4,W/2,H/2);
// int startAngle = 90 * 16; //起始90°
// int spanAngle = 90 * 16; //旋转90°
// painter.drawArc(rect, startAngle, spanAngle);
//2. drawChord()
// QRect rect(W/4,H/4,W/2,H/2);
// int startAngle = 90 * 16; //起始90°
// int spanAngle = 90 * 16; //旋转90°
// painter.drawChord(rect, startAngle, spanAngle);
//3.drawConvexPolygon()
// QPoint points[4]={
// QPoint(5*W/12,H/4),
QPoint(7*W/12,H/4),
// QPoint(3*W/4,5*H/12),
QPoint(3*W/4,7*H/12),
QPoint(7*W/12,3*H/4),
// QPoint(5*W/12,3*H/4),
QPoint(W/4,7*H/12),
// QPoint(W/4,5*H/12),
QPoint(5*W/12,H/4)
// };
// painter.drawConvexPolygon(points, 4);
//4. drawEllipse
// QRect rect(W/4,H/4,W/2,H/2);
// painter.drawEllipse(rect);
//5. drawImage
// QRect rect(W/4,H/4,W/2,H/2);
// QImage image(":images/images/qt.jpg");
// painter.drawImage(rect, image);
//6. drawLine
// QLine Line(W/4,H/4,W/2,H/2);
// painter.drawLine(Line);
//7. drawLines
// QRect rect(W/4,H/4,W/2,H/2);
// QVector Lines;
// Lines.append(QLine(rect.topLeft(),rect.bottomRight()));
// Lines.append(QLine(rect.topRight(),rect.bottomLeft()));
// Lines.append(QLine(rect.topLeft(),rect.bottomLeft()));
// Lines.append(QLine(rect.topRight(),rect.bottomRight()));
// painter.drawLines(Lines);
// 8.QPainterPath
// QRect rect(W/4,H/4,W/2,H/2);
// QPainterPath path;
// path.addEllipse(rect);
// path.addRect(rect);
// painter.drawPath(path);
//9.drawPie
// QRect rect(W/4,H/4,W/2,H/2);
// int startAngle = 40 * 16;//起始40°
// int spanAngle = 120 * 16;//旋转120°
// painter.drawPie(rect, startAngle, spanAngle);
//10. drawPixmap
// QRect rect(W/4,H/4,W/2,H/2);
// QPixmap pixmap(":images/images/qt.jpg");
// painter.drawPixmap(rect, pixmap);
//11. drawPolygon
// QPoint points[]={
// QPoint(5*W/12,H/4),
// QPoint(3*W/4,5*H/12),
// QPoint(5*W/12,3*H/4),
// QPoint(2*W/4,5*H/12),
// };
// painter.drawPolygon(points, 4);
//12.drawPolyline
// QPoint points[]={
// QPoint(5*W/12,H/4),
// QPoint(3*W/4,5*H/12),
// QPoint(5*W/12,3*H/4),
// QPoint(2*W/4,5*H/12)
// };
// painter.drawPolyline(points, 4);
//13.drawRect
// QRect rect(W/4,H/4,W/2,H/2);
// painter.drawRect(rect);
//14.drawRect
// QRect rect(W/4,H/4,W/2,H/2);
// painter.drawRoundedRect(rect,20,20);
//14.drawRect
// QRect rect(W/4,H/4,W/2,H/2);
// QFont font;
// font.setPointSize(30);
// font.setBold(true);
// painter.setFont(font);
// painter.drawText (rect,"Hello,Qt");
//. eraseRect
// QRect rect(W/4,H/4,W/2,H/2);
// painter.eraseRect(rect);
//15. fillRect
QRect rect(W/4,H/4,W/2,H/2);
painter.fillRect (rect,Qt::green);
//16. fillPath
// QRect rect(W/4,H/4,W/2,H/2);
// QPainterPath path;
// path.addEllipse(rect);
// path.addRect(rect);
// painter.fillPath(path,Qt::red);
//17.drawPoint
// painter.drawPoint(QPoint(W/2,H/2));
//18. drawPoints
// QPoint points[]={
// QPoint(5*W/12,H/4),
// QPoint(3*W/4,5*H/12),
// QPoint(2*W/4,5*H/12)
// };
// painter.drawPoints(points, 3);
}
绘制图片：
// QPixmap pixmap;
// pixmap.load(":/images/images/qt.jpg");
// painter.drawPixmap(rect.left(),rect.top(),pixmap);