qwt_plot_vectorfield.cpp

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/******************************************************************************
 * Qwt Widget Library
 * Copyright (C) 1997   Josef Wilgen
 * Copyright (C) 2002   Uwe Rathmann
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the Qwt License, Version 1.0
 *****************************************************************************/

#include "qwt_plot_vectorfield.h"
#include "qwt_vectorfield_symbol.h"
#include "qwt_scale_map.h"
#include "qwt_color_map.h"
#include "qwt_painter.h"
#include "qwt_text.h"
#include "qwt_graphic.h"
#include "qwt_math.h"

#include <qpainter.h>
#include <qpainterpath.h>
#include <qdebug.h>
#include <cstdlib>
#include <limits>

#define DEBUG_RENDER 0

#if DEBUG_RENDER
#include <qelapsedtimer.h>
#endif


static inline double qwtVector2Radians( double vx, double vy )
{
    if ( vx == 0.0 )
        return ( vy >= 0 ) ? M_PI_2 : 3 * M_PI_2;

    return std::atan2( vy, vx );
}

static inline double qwtVector2Magnitude( double vx, double vy )
{
    return sqrt( vx * vx + vy * vy );
}

static QwtInterval qwtMagnitudeRange(
    const QwtSeriesData< QwtVectorFieldSample >* series )
{
    if ( series->size() == 0 )
        return QwtInterval( 0, 1 );

    const QwtVectorFieldSample s0 = series->sample( 0 );

    double min = s0.vx * s0.vx + s0.vy * s0.vy;
    double max = min;

    for ( uint i = 1; i < series->size(); i++ )
    {
        const QwtVectorFieldSample s = series->sample( i );
        const double l = s.vx * s.vx + s.vy * s.vy;

        if ( l < min )
            min = l;

        if ( l > max )
            max = l;
    }

    min = std::sqrt( min );
    max = std::sqrt( max );

    if ( max == min )
        max += 1.0;

    return QwtInterval( min, max );
}

static inline QTransform qwtSymbolTransformation(
    const QTransform& oldTransform, double x, double y,
    double vx, double vy, double magnitude )
{
    QTransform transform = oldTransform;

    if ( !transform.isIdentity() )
    {
        transform.translate( x, y );

        const double radians = qwtVector2Radians( vx, vy );
        transform.rotateRadians( radians );
    }
    else
    {
        /*
            When starting with no transformation ( f.e on screen )
            the matrix can be found without having to use
            trigonometric functions
         */

        qreal sin, cos;
        if ( magnitude == 0.0 )
        {
            // something
            sin = 1.0;
            cos = 0.0;
        }
        else
        {
            sin = vy / magnitude;
            cos = vx / magnitude;
        }

        transform.setMatrix( cos, sin, 0.0, -sin, cos, 0.0, x, y, 1.0 );
    }

    return transform;
}

namespace
{
    class FilterMatrix
    {
      public:
        class Entry
        {
          public:
            inline void addSample( double sx, double sy,
                double svx, double svy )
            {
                x += sx;
                y += sy;

                vx += svx;
                vy += svy;

                count++;
            }

            quint32 count;

            // screen positions -> float is good enough
            float x;
            float y;
            float vx;
            float vy;
        };

        FilterMatrix( const QRectF& dataRect,
            const QRectF& canvasRect, const QSizeF& cellSize )
        {
            m_dx = cellSize.width();
            m_dy = cellSize.height();

            m_x0 = dataRect.x();
            if ( m_x0 < canvasRect.x() )
                m_x0 += int( ( canvasRect.x() - m_x0 ) / m_dx ) * m_dx;

            m_y0 = dataRect.y();
            if ( m_y0 < canvasRect.y() )
                m_y0 += int( ( canvasRect.y() - m_y0 ) / m_dy ) * m_dy;

            m_numColumns = canvasRect.width() / m_dx + 1;
            m_numRows = canvasRect.height() / m_dy + 1;

#if 1
            /*
                limit column and row count to a maximum of 1000000,
                so that memory usage is not an issue
             */
            if ( m_numColumns > 1000 )
            {
                m_dx = canvasRect.width() / 1000;
                m_numColumns = canvasRect.width() / m_dx + 1;
            }

            if ( m_numRows > 1000 )
            {
                m_dy = canvasRect.height() / 1000;
                m_numRows = canvasRect.height() / m_dx + 1;
            }
#endif

            m_x1 = m_x0 + m_numColumns * m_dx;
            m_y1 = m_y0 + m_numRows * m_dy;

            m_entries = ( Entry* )::calloc( m_numRows * m_numColumns, sizeof( Entry ) );
            if ( m_entries == NULL )
            {
                qWarning() << "QwtPlotVectorField: raster for filtering too fine - running out of memory";
            }
        }

        ~FilterMatrix()
        {
            if ( m_entries )
                std::free( m_entries );
        }

        inline int numColumns() const
        {
            return m_numColumns;
        }

        inline int numRows() const
        {
            return m_numRows;
        }

        inline void addSample( double x, double y,
            double u, double v )
        {
            if ( x >= m_x0 && x < m_x1
                && y >= m_y0 && y < m_y1 )
            {
                Entry& entry = m_entries[ indexOf( x, y ) ];
                entry.addSample( x, y, u, v );
            }
        }

        const FilterMatrix::Entry* entries() const
        {
            return m_entries;
        }

      private:
        inline int indexOf( qreal x, qreal y ) const
        {
            const int col = ( x - m_x0 ) / m_dx;
            const int row = ( y - m_y0 ) / m_dy;

            return row * m_numColumns + col;
        }

        qreal m_x0, m_x1, m_y0, m_y1, m_dx, m_dy;
        int m_numColumns;
        int m_numRows;

        Entry* m_entries;
    };
}

class QwtPlotVectorField::PrivateData
{
  public:
    PrivateData()
        : pen( Qt::black )
        , brush( Qt::black )
        , indicatorOrigin( QwtPlotVectorField::OriginHead )
        , magnitudeScaleFactor( 1.0 )
        , rasterSize( 20, 20 )
        , minArrowLength( 0.0 )
        , maxArrowLength( std::numeric_limits< short >::max() )
        , magnitudeModes( MagnitudeAsLength )
    {
        colorMap = NULL;
        symbol = new QwtVectorFieldThinArrow();
    }

    ~PrivateData()
    {
        delete colorMap;
        delete symbol;
    }

    QPen pen;
    QBrush brush;

    IndicatorOrigin indicatorOrigin;
    QwtVectorFieldSymbol* symbol;
    QwtColorMap* colorMap;

    /*
        Stores the range of magnitudes to be used for the color map.
        If invalid (min=max or negative values), the range is determined
        from the data samples themselves.
     */
    QwtInterval magnitudeRange;
    QwtInterval boundingMagnitudeRange;

    qreal magnitudeScaleFactor;
    QSizeF rasterSize;

    double minArrowLength;
    double maxArrowLength;

    PaintAttributes paintAttributes;
    MagnitudeModes magnitudeModes;
};

QwtPlotVectorField::QwtPlotVectorField( const QwtText& title )
    : QwtPlotSeriesItem( title )
{
    init();
}

QwtPlotVectorField::QwtPlotVectorField( const QString& title )
    : QwtPlotSeriesItem( QwtText( title ) )
{
    init();
}

QwtPlotVectorField::~QwtPlotVectorField()
{
    delete m_data;
}

void QwtPlotVectorField::init()
{
    setItemAttribute( QwtPlotItem::Legend );
    setItemAttribute( QwtPlotItem::AutoScale );

    m_data = new PrivateData;
    setData( new QwtVectorFieldData() );

    setZ( 20.0 );
}

void QwtPlotVectorField::setPen( const QPen& pen )
{
    if ( m_data->pen != pen )
    {
        m_data->pen = pen;

        itemChanged();
        legendChanged();
    }
}

QPen QwtPlotVectorField::pen() const
{
    return m_data->pen;
}

void QwtPlotVectorField::setBrush( const QBrush& brush )
{
    if ( m_data->brush != brush )
    {
        m_data->brush = brush;

        itemChanged();
        legendChanged();
    }
}

QBrush QwtPlotVectorField::brush() const
{
    return m_data->brush;
}

void QwtPlotVectorField::setIndicatorOrigin( IndicatorOrigin origin )
{
    m_data->indicatorOrigin = origin;
    if ( m_data->indicatorOrigin != origin )
    {
        m_data->indicatorOrigin = origin;
        itemChanged();
    }
}

QwtPlotVectorField::IndicatorOrigin QwtPlotVectorField::indicatorOrigin() const
{
    return m_data->indicatorOrigin;
}

void QwtPlotVectorField::setMagnitudeScaleFactor( double factor )
{
    if ( factor != m_data->magnitudeScaleFactor )
    {
        m_data->magnitudeScaleFactor = factor;
        itemChanged();
    }
}

double QwtPlotVectorField::magnitudeScaleFactor() const
{
    return m_data->magnitudeScaleFactor;
}

void QwtPlotVectorField::setRasterSize( const QSizeF& size )
{
    if ( size != m_data->rasterSize )
    {
        m_data->rasterSize = size;
        itemChanged();
    }
}

QSizeF QwtPlotVectorField::rasterSize() const
{
    return m_data->rasterSize;
}

void QwtPlotVectorField::setPaintAttribute(
    PaintAttribute attribute, bool on )
{
    PaintAttributes attributes = m_data->paintAttributes;

    if ( on )
        attributes |= attribute;
    else
        attributes &= ~attribute;

    if ( m_data->paintAttributes != attributes )
    {
        m_data->paintAttributes = attributes;
        itemChanged();
    }
}

bool QwtPlotVectorField::testPaintAttribute(
    PaintAttribute attribute ) const
{
    return ( m_data->paintAttributes & attribute );
}

int QwtPlotVectorField::rtti() const
{
    return QwtPlotItem::Rtti_PlotVectorField;
}

void QwtPlotVectorField::setSymbol( QwtVectorFieldSymbol* symbol )
{
    if ( m_data->symbol == symbol )
        return;

    delete m_data->symbol;
    m_data->symbol = symbol;

    itemChanged();
    legendChanged();
}

const QwtVectorFieldSymbol* QwtPlotVectorField::symbol() const
{
    return m_data->symbol;
}

void QwtPlotVectorField::setSamples( const QVector< QwtVectorFieldSample >& samples )
{
    setData( new QwtVectorFieldData( samples ) );
}

void QwtPlotVectorField::setSamples( QwtVectorFieldData* data )
{
    setData( data );
}

void QwtPlotVectorField::setColorMap( QwtColorMap* colorMap )
{
    if ( colorMap == NULL )
        return;

    if ( colorMap != m_data->colorMap )
    {
        delete m_data->colorMap;
        m_data->colorMap = colorMap;
    }

    legendChanged();
    itemChanged();
}

const QwtColorMap* QwtPlotVectorField::colorMap() const
{
    return m_data->colorMap;
}

void QwtPlotVectorField::setMagnitudeMode( MagnitudeMode mode, bool on )
{
    if ( on == testMagnitudeMode( mode ) )
        return;

    if ( on )
        m_data->magnitudeModes |= mode;
    else
        m_data->magnitudeModes &= ~mode;

    itemChanged();
}

bool QwtPlotVectorField::testMagnitudeMode( MagnitudeMode mode ) const
{
    return m_data->magnitudeModes & mode;
}

void QwtPlotVectorField::setMagnitudeRange( const QwtInterval& magnitudeRange )
{
    if ( m_data->magnitudeRange != magnitudeRange )
    {
        m_data->magnitudeRange = magnitudeRange;
        itemChanged();
    }
}

QwtInterval QwtPlotVectorField::magnitudeRange() const
{
    return m_data->magnitudeRange;
}

void QwtPlotVectorField::setMinArrowLength( double length )
{
    length = qMax( length, 0.0 );

    if ( m_data->minArrowLength != length )
    {
        m_data->minArrowLength = length;
        itemChanged();
    }
}

double QwtPlotVectorField::minArrowLength() const
{
    return m_data->minArrowLength;
}

void QwtPlotVectorField::setMaxArrowLength( double length )
{
    length = qMax( length, 0.0 );

    if ( m_data->maxArrowLength != length )
    {
        m_data->maxArrowLength = length;
        itemChanged();
    }
}

double QwtPlotVectorField::maxArrowLength() const
{
    return m_data->maxArrowLength;
}

double QwtPlotVectorField::arrowLength( double magnitude ) const
{
#if 0
    /*
       Normalize magnitude with respect to value range.  Then, magnitudeScaleFactor
       is the number of pixels to draw for a vector of length equal to
       magnitudeRange.maxValue(). The relative scaling ensures that change of data
       samples of very different magnitudes will always lead to a reasonable
       display on screen.
     */
    const QwtVectorFieldData* vectorData = dynamic_cast< const QwtVectorFieldData* >( data() );
    if ( m_data->magnitudeRange.maxValue() > 0 )
        magnitude /= m_data->magnitudeRange.maxValue();
#endif

    double length = magnitude * m_data->magnitudeScaleFactor;

    if ( length > 0.0 )
        length = qBound( m_data->minArrowLength, length, m_data->maxArrowLength );

    return length;
}

QRectF QwtPlotVectorField::boundingRect() const
{
#if 0
    /*
        The bounding rectangle of the samples comes from the origins
        only, but as we know the scaling factor for the magnitude
        ( qwtVector2Magnitude ) here, we could try to include it ?
     */
#endif

    return QwtPlotSeriesItem::boundingRect();
}

QwtGraphic QwtPlotVectorField::legendIcon(
    int index, const QSizeF& size ) const
{
    Q_UNUSED( index );

    QwtGraphic icon;
    icon.setDefaultSize( size );

    if ( size.isEmpty() )
        return icon;

    QPainter painter( &icon );
    painter.setRenderHint( QPainter::Antialiasing,
        testRenderHint( QwtPlotItem::RenderAntialiased ) );

    painter.translate( -size.width(), -0.5 * size.height() );

    painter.setPen( m_data->pen );
    painter.setBrush( m_data->brush );

    m_data->symbol->setLength( size.width() - 2 );
    m_data->symbol->paint( &painter );

    return icon;
}

void QwtPlotVectorField::drawSeries( QPainter* painter,
    const QwtScaleMap& xMap, const QwtScaleMap& yMap,
    const QRectF& canvasRect, int from, int to ) const
{
    if ( !painter || dataSize() <= 0 )
        return;

    if ( to < 0 )
        to = dataSize() - 1;

    if ( from < 0 )
        from = 0;

    if ( from > to )
        return;

#if DEBUG_RENDER
    QElapsedTimer timer;
    timer.start();
#endif

    drawSymbols( painter, xMap, yMap, canvasRect, from, to );

#if DEBUG_RENDER
    qDebug() << timer.elapsed();
#endif
}

void QwtPlotVectorField::drawSymbols( QPainter* painter,
    const QwtScaleMap& xMap, const QwtScaleMap& yMap,
    const QRectF& canvasRect, int from, int to ) const
{
    const bool doAlign = QwtPainter::roundingAlignment( painter );
    const bool doClip = false;

    const bool isInvertingX = xMap.isInverting();
    const bool isInvertingY = yMap.isInverting();

    const QwtSeriesData< QwtVectorFieldSample >* series = data();

    if ( m_data->magnitudeModes & MagnitudeAsColor )
    {
        // user input error, can't draw without color map
        // TODO: Discuss! Without colormap, silently fall back to uniform colors?
        if ( m_data->colorMap == NULL)
            return;
    }
    else
    {
        painter->setPen( m_data->pen );
        painter->setBrush( m_data->brush );
    }

    if ( ( m_data->paintAttributes & FilterVectors ) && !m_data->rasterSize.isEmpty() )
    {
        const QRectF dataRect = QwtScaleMap::transform(
            xMap, yMap, boundingRect() );

        // TODO: Discuss. How to handle raster size when switching from screen to print size!
        //       DPI-aware adjustment of rastersize? Or make "rastersize in screen coordinate"
        //       or "rastersize in plotcoordinetes" a user option?
#if 1
        // define filter matrix based on screen/print coordinates
        FilterMatrix matrix( dataRect, canvasRect, m_data->rasterSize );
#else
        // define filter matrix based on real coordinates

        // get scale factor from real coordinates to screen coordinates
        double xScale = 1;
        if (xMap.sDist() != 0)
            xScale = xMap.pDist() / xMap.sDist();

        double yScale = 1;
        if (yMap.sDist() != 0)
            yScale = yMap.pDist() / yMap.sDist();

        QSizeF canvasRasterSize(xScale * m_data->rasterSize.width(), yScale * m_data->rasterSize.height() );
        FilterMatrix matrix( dataRect, canvasRect, canvasRasterSize );
#endif

        for ( int i = from; i <= to; i++ )
        {
            const QwtVectorFieldSample sample = series->sample( i );
            if ( !sample.isNull() )
            {
                matrix.addSample( xMap.transform( sample.x ),
                    yMap.transform( sample.y ), sample.vx, sample.vy );
            }
        }

        const int numEntries = matrix.numRows() * matrix.numColumns();
        const FilterMatrix::Entry* entries = matrix.entries();

        for ( int i = 0; i < numEntries; i++ )
        {
            const FilterMatrix::Entry& entry = entries[i];

            if ( entry.count == 0 )
                continue;

            double xi = entry.x / entry.count;
            double yi = entry.y / entry.count;

            if ( doAlign )
            {
                xi = qRound( xi );
                yi = qRound( yi );
            }

            const double vx = entry.vx / entry.count;
            const double vy = entry.vy / entry.count;

            drawSymbol( painter, xi, yi,
                isInvertingX ? -vx : vx, isInvertingY ? -vy : vy );
        }
    }
    else
    {
        for ( int i = from; i <= to; i++ )
        {
            const QwtVectorFieldSample sample = series->sample( i );

            // arrows with zero length are never drawn
            if ( sample.isNull() )
                continue;

            double xi = xMap.transform( sample.x );
            double yi = yMap.transform( sample.y );

            if ( doAlign )
            {
                xi = qRound( xi );
                yi = qRound( yi );
            }

            if ( doClip )
            {
                if ( !canvasRect.contains( xi, yi ) )
                    continue;
            }

            drawSymbol( painter, xi, yi,
                isInvertingX ? -sample.vx : sample.vx,
                isInvertingY ? -sample.vy : sample.vy );
        }
    }
}

void QwtPlotVectorField::drawSymbol( QPainter* painter,
    double x, double y, double vx, double vy ) const
{
    const double magnitude = qwtVector2Magnitude( vx, vy );

    const QTransform oldTransform = painter->transform();

    QTransform transform = qwtSymbolTransformation( oldTransform,
        x, y, vx, vy, magnitude );

    QwtVectorFieldSymbol* symbol = m_data->symbol;

    double length = 0.0;

    if ( m_data->magnitudeModes & MagnitudeAsLength )
    {
        length = arrowLength( magnitude );
    }

    symbol->setLength( length );

    if( m_data->indicatorOrigin == OriginTail )
    {
        const qreal dx = symbol->length();
        transform.translate( dx, 0.0 );
    }
    else if ( m_data->indicatorOrigin == OriginCenter )
    {
        const qreal dx = symbol->length();
        transform.translate( 0.5 * dx, 0.0 );
    }

    if ( m_data->magnitudeModes & MagnitudeAsColor )
    {
        // Determine color for arrow if colored by magnitude.

        QwtInterval range = m_data->magnitudeRange;

        if ( !range.isValid() )
        {
            if ( !m_data->boundingMagnitudeRange.isValid() )
                m_data->boundingMagnitudeRange = qwtMagnitudeRange( data() );

            range = m_data->boundingMagnitudeRange;
        }

        const QColor c = m_data->colorMap->rgb( range, magnitude );

#if 1
        painter->setBrush( c );
        painter->setPen( c );
#endif
    }

    painter->setWorldTransform( transform, false );
    symbol->paint( painter );
    painter->setWorldTransform( oldTransform, false );
}

void QwtPlotVectorField::dataChanged()
{
    m_data->boundingMagnitudeRange.invalidate();
    QwtPlotSeriesItem::dataChanged();
}