1.概述
QwtPolarPlot是Qwt库中用于绘制极坐标图的类。它继承自QwtPolarItemDict和QFrame类,并且可以作为QwtPlot控件的一部分使用。
以下是类的继承关系图:
2.常用方法
设置标签:
- void setTitle (const QString &)
- void setTitle (const QwtText &)
设置范围:
- void setScale (int scaleId, double min, double max, double step=0)
设置主刻度间隔的最大数量:
- void setScaleMaxMinor (int scaleId, int maxMinor)
设置背景色:
- void setPlotBackground (const QBrush &c)
插入图例:
- void insertLegend (QwtAbstractLegend *, LegendPosition=RightLegend, double ratio=-1.0)
3.示例
源码:画Rose曲线时QwtPolarCurve设置的数据类型是**QwtSeriesData< QwtPointPolar >,**QwtSeriesData< QwtPointPolar >中有三个纯虚函数需要我们来实现,分别是
- virtual size_t size () const =0
- virtual QwtPointPolar sample (size_t i) const =0
- virtual QRectF boundingRect () const =0
cpp
#include "PolarPlotWidget.h"
#include "ui_PolarPlotWidget.h"
#include "qwt_plot.h"
#include "qwt_plot_curve.h"
#include "qwt_text.h"
#include "qwt_legend.h"
#include "qwt_symbol.h"
#include "qwt_plot_marker.h"
#include "qwt_plot_grid.h"
#include "qwt_scale_div.h"
#include "qwt_plot_canvas.h"
#include "qwt_plot_legenditem.h"
#include "qwt_math.h"
#include "qwt_plot_layout.h"
#include "qwt_plot_barchart.h"
#include "qwt_scale_draw.h"
#include "qwt_column_symbol.h"
#include "qwt_plot_renderer.h"
#include "qwt_plot_multi_barchart.h"
#include "qwt_polar_plot.h"
#include "qwt_polar_grid.h"
#include "qwt_polar_marker.h"
#include "qwt_polar_curve.h"
class Data : public QwtSeriesData< QwtPointPolar >
{
public:
Data( const QwtInterval& radialInterval,
const QwtInterval& azimuthInterval, size_t size )
: m_radialInterval( radialInterval )
, m_azimuthInterval( azimuthInterval )
, m_size( size )
{
}
virtual size_t size() const QWT_OVERRIDE
{
return m_size;
}
protected:
QwtInterval m_radialInterval;
QwtInterval m_azimuthInterval;
size_t m_size;
};
class RoseData : public Data
{
public:
RoseData( const QwtInterval& radialInterval,
const QwtInterval& azimuthInterval, size_t size )
: Data( radialInterval, azimuthInterval, size )
{
}
virtual QwtPointPolar sample( size_t i ) const QWT_OVERRIDE
{
const double stepA = m_azimuthInterval.width() / m_size;
const double a = m_azimuthInterval.minValue() + i * stepA;
const double d = a / 360.0 * M_PI;
const double r = m_radialInterval.maxValue() * qAbs( qSin( 4 * d ) );
return QwtPointPolar( a, r );
}
virtual QRectF boundingRect() const QWT_OVERRIDE
{
if ( cachedBoundingRect.width() < 0.0 )
cachedBoundingRect = qwtBoundingRect( *this );
return cachedBoundingRect;
}
};
static QwtPolarPlot *g_plot = nullptr;
static QwtPolarGrid *g_grid = nullptr;
static const QwtInterval s_radialInterval( 0.0, 10.0 );
static const QwtInterval s_azimuthInterval( 0.0, 360.0 );
PolarPlotWidget::PolarPlotWidget(QWidget *parent) :
QWidget(parent),
ui(new Ui::PolarPlotWidget)
{
ui->setupUi(this);
g_plot = new QwtPolarPlot(QwtText( "Polar Plot Demo" ), this);
g_plot->setAutoReplot( false );
g_plot->setPlotBackground( Qt::darkBlue );
ui->verticalLayout->addWidget(g_plot);
//设置角度范围
g_plot->setScale( QwtPolar::Azimuth,
s_azimuthInterval.minValue(), s_azimuthInterval.maxValue(),
s_azimuthInterval.width() / 12 );
g_plot->setScaleMaxMinor( QwtPolar::Azimuth, 2 );
//设置半径范围
g_plot->setScale( QwtPolar::Radius,
s_radialInterval.minValue(), s_radialInterval.maxValue() );
// 设置网格效果属性
g_grid = new QwtPolarGrid();
g_grid->setPen( QPen( Qt::white ) );
for ( int scaleId = 0; scaleId < QwtPolar::ScaleCount; scaleId++ )
{
g_grid->showGrid( scaleId );
g_grid->showMinorGrid( scaleId );
QPen minorPen( Qt::gray );
g_grid->setMinorGridPen( scaleId, minorPen );
}
g_grid->setAxisPen( QwtPolar::AxisAzimuth, QPen( Qt::black ) );
g_grid->showAxis( QwtPolar::AxisAzimuth, true );
g_grid->showAxis( QwtPolar::AxisLeft, false );
g_grid->showAxis( QwtPolar::AxisRight, true );
g_grid->showAxis( QwtPolar::AxisTop, true );
g_grid->showAxis( QwtPolar::AxisBottom, false );
g_grid->showGrid( QwtPolar::Azimuth, true );
g_grid->showGrid( QwtPolar::Radius, true );
g_grid->attach( g_plot );
// 设置曲线
const int numPoints = 200;
QwtPolarCurve* curve = new QwtPolarCurve();
curve->setStyle( QwtPolarCurve::Lines );
curve->setTitle( "Rose" );
curve->setPen( QPen( Qt::red, 2 ) );
curve->setSymbol( new QwtSymbol( QwtSymbol::Rect,
QBrush( Qt::cyan ), QPen( Qt::white ), QSize( 3, 3 ) ) );
curve->setData(
new RoseData( s_radialInterval, s_azimuthInterval, numPoints ) );
curve->attach( g_plot );
// 设置标记
QwtPolarMarker* marker = new QwtPolarMarker();
marker->setPosition( QwtPointPolar( 57.3, 4.72 ) );
marker->setSymbol( new QwtSymbol( QwtSymbol::Ellipse,
QBrush( Qt::white ), QPen( Qt::green ), QSize( 9, 9 ) ) );
marker->setLabelAlignment( Qt::AlignHCenter | Qt::AlignTop );
QwtText text( "Marker" );
text.setColor( Qt::black );
QColor bg( Qt::white );
bg.setAlpha( 200 );
text.setBackgroundBrush( QBrush( bg ) );
marker->setLabel( text );
marker->attach( g_plot );
QwtLegend* legend = new QwtLegend;
g_plot->insertLegend( legend, QwtPolarPlot::BottomLegend );
}
PolarPlotWidget::~PolarPlotWidget()
{
delete ui;
}