Qt QPainter基本绘图
QPainter绘图操作类。
QPainterDevice使用QPainter绘图的抽象二维界面（绘图设备），包括QWidget、QPixmap、QImage等。
QPaintEngine给QPainter提供不同设备绘图的接口，QPainter和QPainterDevice内部使用，创建自己的设备类型时才需要。
paintEvent使用QWidget绘图区的局部物理坐标，视口（viewport）坐标。
QPen
线条颜色、宽度、线型等。
void setWidth(int width);
void setColor(QColor &color);
//Qt::NoPen, Qt::SolidLine,
//Qt::DashLine, Qt::DotLine,
//Qt::DashDotLine, Qt::DashDotDotLine, Qt::CustomDashLine
//自定义样式setDashOffset(), setDashPattern()
void setStyle(Qt::PenStyle style);//线的类型，实线、虚线等
//Qt::FlatCap, Qt::SquareCap, Qt::RoundCap
void setCapStyle(Qt::PenCapStyle style);//线的端点样式
//Qt::MiterJoin, Qt::BevelJoin,Qt::RoundJoin, Qt::SvgMiterJoin
void setJoinStyle(Qt::PenJoinStyle style);//线的连接点样式
QBrush
区域填充特性，颜色、填充方式、渐变特性、图片填充等。
void setColor(QColor &color);
//Qt::NoBrush, Qt::SolidPattern,
//Qt::Dense1Pattern, Qt::Dense2Pattern, ..., Qt::Dense7Pattern,
//Qt::HorPattern, Qt::VerPattern, Qt::CrossPattern,
//Qt::BDiagPattern, Qt::FDiagPattern, Qt::DiagCrossPattern,
//Qt::LinearGradientPattern, 需设置setBrush(QLinearGradient)
//Qt::ConicalGradientPattern, 需设置setBrush(QConicalGradient)
//Qt::RadialGradientPattern, 需设置setBrush(QRadialGradient)
//Qt::TexturePattern, 需设置setTexture或setTextureImage, style自动设置为Qt::TexturePattern
void setStyle(Qt::BrushStyle style);
void setTexture(QPixmax &pixmap);
void setTextureImage(QImage &image);
渐变填充
基类QGradient，setSpread(QGradient::Spread method)设置延展方式，对（QConicalGradient）圆锥型渐变不起作用。
- QGradient::PadSpread
结束点颜色填充外部区域，缺省方式。 - QGradient::RepeatSpread
重复方式填充外部区域。 - QGradient::ReflectSpread
反射式重复方式填充外部区域。
3个实现渐变填充的类：
- QLinearGradient
线性渐变，指定起点，终点，中间点及颜色，线性插值计算得到所有点填充色。 - QRadialGradient
简单辐射渐变，圆内焦点和端点间生成渐变色。扩展辐射渐变，焦点圆和中心圆间生成渐变色。 - QConicalGradient
圆锥形渐变，中心点逆时针生成渐变色。
//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::blue);//中间点颜色
linearGrad.setColorAt(1, Qt::red);//终点颜色
linearGrad.setSpread(QGradient::ReflectSpread); //展布模式
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::green);
radialGrad.setColorAt(1, Qt::blue);
radialGrad.setSpread(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);
QFont
文字样式、大小等。
基本图形元件
QPainter painter(this);
int W = width();
int H = height();
- drawArc，弧线
QRect rect(W/4, H/4, W/2, H/2);
int startAngle = 90 * 16; //起始90°，上
int spanAngle = 90 * 16; //旋转90°，左
painter.drawArc(rect, startAngle, spanAngle);
- drawChord，弦
QRect rect(W/4, H/4, W/2, H/2);
int startAngle = 90 * 16; //起始90°，上
int spanAngle = 90 * 16; //旋转90°，左
painter.drawChord(rect, startAngle, spanAngle);
- drawConvexPolygon，给定点画凸多边形
QPoint points[4] = {
QPoint(5*W/12, H/4),
QPoint(3*W/4, 5*H/12),
QPoint(5*W/12, 3*H/4),
QPoint(W/4, 5*H/12),
};
painter.drawConvexPolygon(points, 4);
- drawEllipse，椭圆
QRect rect(W/4, H/4, W/2, H/2);
painter.drawEllipse(rect);
- drawImage，image图片
QRect rect(W/4, H/4, W/2, H/2);
painter.drawImage(rect, QImage("qt.jpg"));
+drawLine，线
QLine Line(W/4, H/4, W/2, H/2);
painter.drawLine(Line);
- drawLines，一批线
QRect rect(W/4, H/4, W/2, H/2);
QVector<QLine> 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);
- drawPath，路径
QRect rect(W/4, H/4, W/2, H/2);
QPainterPath path;
path.addEllipse(rect);
path.addRect(rect);
painter.drawPath(path);
- drawPie，扇形
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);
- drawPixmap，pixmap图片
QRect rect(W/4, H/4, W/2, H/2);
painter.drawPixmap(rect, QPixmap("qt.jpg"));
- drawPoint，点
painter.drawPoint(QPoint(W/2, H/2));
- drawPoints，一批点
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);
- drawPolygon，多边形
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);
- drawPolyline，多边形的线
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);
- drawRect，矩形
QRect rect(W/4, H/4, W/2, H/2);
painter.drawRect(rect);
- drawRoundedRect，圆角矩形
QRect rect(W/4, H/4, W/2, H/2);
painter.drawRoundedRect(rect, 20, 20);
- drawText，单行文本
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，擦除矩形，背景色填充
QRect rect(W/4, H/4, W/2, H/2);
painter.eraseRect(rect);
- fillPath，填充路径，轮廓线不显示
QRect rect(W/4, H/4, W/2, H/2);
QPainterPath path;
path.addEllipse(rect);
path.addRect(rect);
painter.fillPath(path, Qt::red);
- fillRect，填充矩形，无边框线
QRect rect(W/4, H/4, W/2, H/2);
painter.fillRect(rect, Qt::green);
QPainterPath
五角星路径
qreal R = 100; //半径
const qreal Pi = 3.14159;
qreal deg = Pi*72/180;
QPoint points[5] = {
QPoint(R, 0),
QPoint(R*std::cos(deg), -R*std::sin(deg)),
QPoint(R*std::cos(2*deg), -R*std::sin(2*deg)),
QPoint(R*std::cos(3*deg), -R*std::sin(3*deg)),
QPoint(R*std::cos(4*deg), -R*std::sin(4*deg)),
};
QPainterPath starPath;
starPath.moveTo(points[0]);
starPath.lineTo(points[2]);
starPath.lineTo(points[4]);
starPath.lineTo(points[1]);
starPath.lineTo(points[3]);
starPath.closeSubpath();
QPoint points[9] = {
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)
};
QPainterPath path;
path.addRect(rect);
path.addEllipse(rect);
path.moveTo(points[0]);
path.lineTo(points[4]);
path.moveTo(points[1]);
path.lineTo(points[5]);
path.moveTo(points[2]);
path.lineTo(points[6]);
path.moveTo(points[3]);
path.lineTo(points[7]);
path.moveTo(points[0]);
path.cubicTo(points[1], points[4], points[2]);
QPainter::CompositionMode
enum CompositionMode {
CompositionMode_SourceOver,
CompositionMode_DestinationOver,
CompositionMode_Clear,
CompositionMode_Source,
CompositionMode_Destination,
CompositionMode_SourceIn,
CompositionMode_DestinationIn,
CompositionMode_SourceOut,
CompositionMode_DestinationOut,
CompositionMode_SourceAtop,
CompositionMode_DestinationAtop,
CompositionMode_Xor,
//svg 1.2 blend modes
CompositionMode_Plus,
CompositionMode_Multiply,
CompositionMode_Screen,
CompositionMode_Overlay,
CompositionMode_Darken,
CompositionMode_Lighten,
CompositionMode_ColorDodge,
CompositionMode_ColorBurn,
CompositionMode_HardLight,
CompositionMode_SoftLight,
CompositionMode_Difference,
CompositionMode_Exclusion,
// ROPs
RasterOp_SourceOrDestination,
RasterOp_SourceAndDestination,
RasterOp_SourceXorDestination,
RasterOp_NotSourceAndNotDestination,
RasterOp_NotSourceOrNotDestination,
RasterOp_NotSourceXorDestination,
RasterOp_NotSource,
RasterOp_NotSourceAndDestination,
RasterOp_SourceAndNotDestination,
RasterOp_NotSourceOrDestination,
RasterOp_SourceOrNotDestination,
RasterOp_ClearDestination,
RasterOp_SetDestination,
RasterOp_NotDestination
};
void setCompositionMode(CompositionMode mode);
实例1
class Widget: public QWidget {
Q_OBJECT
public:
explicit Widget(QWidget *parent = 0);
protected:
void paintEvent(QPaintEvent *event) Q_DECL_OVERRIDE; //虚函数重载
}
Widget::Widget(QWidget *parent) : QWidget(parent) {
setPalette(QPalette(Qt::white));
setAutoFillBackground(true);
resize(400, 400);
}
void Widget::paintEvent(QPaintEvent *event) {
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing);
painter.setRenderHint(QPainter::TextAntialiasing);
QPen pen;
pen.setWidth(3);
pen.setColor(Qt::red);
pen.setStyle(Qt::SolidLine);
pen.setCapStyle(Qt::FlatCap);
pen.setJoinStyle(Qt::BevelJoin);
painter.setPen(pen);
QBrush brush;
brush.setColor(Qt::yellow);
brush.setStyle(Qt::SolidPattern);
painter.setBrush(brush);
QFont font;
font.setPointSize(30);
font.setBold(true);
painter.setFont(font);
int W = width();
int H = height();
QRect rect(W/4, H/4, W/2, H/2);
painter.drawRect(rect);
}