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NAME

       QwtPlotHistogram -

       QwtPlotHistogram represents a series of samples, where an interval is associated with a
       value ( $y = f([x1,x2])$ ).

SYNOPSIS

       #include <qwt_plot_histogram.h>

       Inherits QwtPlotSeriesItem< QwtIntervalSample >.

   Public Types
       enum HistogramStyle { Outline, Columns, Lines, UserStyle =  100 }

   Public Member Functions
       QwtPlotHistogram (const QString &title=QString::null)
       QwtPlotHistogram (const QwtText &title)
       virtual ~QwtPlotHistogram ()
       virtual int rtti () const
       void setPen (const QPen &)
       const QPen & pen () const
       void setBrush (const QBrush &)
       const QBrush & brush () const
       void setSamples (const QVector< QwtIntervalSample > &)
       void setBaseline (double reference)
       double baseline () const
       void setStyle (HistogramStyle style)
       HistogramStyle style () const
       void setSymbol (const QwtColumnSymbol *)
       const QwtColumnSymbol * symbol () const
       virtual void drawSeries (QPainter *p, const QwtScaleMap &xMap, const QwtScaleMap &yMap,
           const QRectF &canvasRect, int from, int to) const
       virtual QRectF boundingRect () const
       virtual void drawLegendIdentifier (QPainter *, const QRectF &) const

   Protected Member Functions
       virtual QwtColumnRect columnRect (const QwtIntervalSample &, const QwtScaleMap &, const
           QwtScaleMap &) const
       virtual void drawColumn (QPainter *, const QwtColumnRect &, const QwtIntervalSample &)
           const
       void drawColumns (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, int from,
           int to) const
       void drawOutline (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, int from,
           int to) const
       void drawLines (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, int from,
           int to) const

Detailed Description

       QwtPlotHistogram represents a series of samples, where an interval is associated with a
       value ( $y = f([x1,x2])$ ).

       The representation depends on the style() and an optional symbol() that is displayed for
       each interval.

       Note:
           The term 'histogram' is used in a different way in the areas of digital image
           processing and statistics. Wikipedia introduces the terms 'image histogram' and 'color
           histogram' to avoid confusions. While 'image histograms' can be displayed by a
           QwtPlotCurve there is no applicable plot item for a 'color histogram' yet.

Member Enumeration Documentation

   enum QwtPlotHistogram::HistogramStyle Histogram styles. The default style is
       QwtPlotHistogram::Columns.
       See also:
           setStyle(), style(), setSymbol(), symbol(), setBaseline()

       Enumerator:

       Outline
              Draw an outline around the area, that is build by all intervals using the pen() and
              fill it with the brush(). The outline style requires, that the intervals are in
              increasing order and not overlapping.

       Columns
              Draw a column for each interval. When a symbol() has been set the symbol is used
              otherwise the column is displayed as plain rectangle using pen() and brush().

       Lines  Draw a simple line using the pen() for each interval.

       UserStyle
              Styles >= UserStyle are reserved for derived classes that overload drawSeries()
              with additional application specific ways to display a histogram.

Constructor & Destructor Documentation

   QwtPlotHistogram::QwtPlotHistogram (const QString &title = QString::null) [explicit]
       Constructor
       Parameters:
           title Title of the histogram.

   QwtPlotHistogram::QwtPlotHistogram (const QwtText &title) [explicit] Constructor
       Parameters:
           title Title of the histogram.

   QwtPlotHistogram::~QwtPlotHistogram () [virtual]
       Destructor.

Member Function Documentation

   double QwtPlotHistogram::baseline () const Returns:
           Value of the baseline

       See also:
           setBaseline()

   QRectF QwtPlotHistogram::boundingRect () const [virtual] Returns:
           Bounding rectangle of all samples. For an empty series the rectangle is invalid.

       Reimplemented from QwtPlotSeriesItem< QwtIntervalSample >.

   const QBrush & QwtPlotHistogram::brush () const Returns:
           Brush used in a style() depending way.

       See also:
           setPen(), brush()

   QwtColumnRect QwtPlotHistogram::columnRect (const QwtIntervalSample &sample, const QwtScaleMap
       &xMap, const QwtScaleMap &yMap) const [protected, virtual] Calculate the area that is
       covered by a sample
       Parameters:
           sample Sample
           xMap Maps x-values into pixel coordinates.
           yMap Maps y-values into pixel coordinates.

       Returns:
           Rectangle, that is covered by a sample

   void QwtPlotHistogram::drawColumn (QPainter *painter, const QwtColumnRect &rect, const
       QwtIntervalSample &sample) const [protected, virtual] Draw a column for a sample in
       Columns style().
       When a symbol() has been set the symbol is used otherwise the column is displayed as plain
       rectangle using pen() and brush().

       Parameters:
           painter Painter
           rect Rectangle where to paint the column in paint device coordinates
           sample Sample to be displayed

       Note:
           In applications, where different intervals need to be displayed in a different way (
           f.e different colors or even using differnt symbols) it is recommended to overload
           drawColumn().

   void QwtPlotHistogram::drawColumns (QPainter *painter, const QwtScaleMap &xMap, const
       QwtScaleMap &yMap, intfrom, intto) const [protected] Draw a histogram in Columns style()
       Parameters:
           painter Painter
           xMap Maps x-values into pixel coordinates.
           yMap Maps y-values into pixel coordinates.
           from Index of the first sample to be painted
           to Index of the last sample to be painted. If to < 0 the histogram will be painted to
           its last point.

       See also:
           setStyle(), style(), setSymbol(), drawColumn()

   void QwtPlotHistogram::drawLegendIdentifier (QPainter *painter, const QRectF &rect) const
       [virtual] Draw a plain rectangle without pen using the brush() as identifier
       Parameters:
           painter Painter
           rect Bounding rectangle for the identifier

       Reimplemented from QwtLegendItemManager.

   void QwtPlotHistogram::drawLines (QPainter *painter, const QwtScaleMap &xMap, const
       QwtScaleMap &yMap, intfrom, intto) const [protected] Draw a histogram in Lines style()
       Parameters:
           painter Painter
           xMap Maps x-values into pixel coordinates.
           yMap Maps y-values into pixel coordinates.
           from Index of the first sample to be painted
           to Index of the last sample to be painted. If to < 0 the histogram will be painted to
           its last point.

       See also:
           setStyle(), style(), setPen()

   void QwtPlotHistogram::drawOutline (QPainter *painter, const QwtScaleMap &xMap, const
       QwtScaleMap &yMap, intfrom, intto) const [protected] Draw a histogram in Outline style()
       Parameters:
           painter Painter
           xMap Maps x-values into pixel coordinates.
           yMap Maps y-values into pixel coordinates.
           from Index of the first sample to be painted
           to Index of the last sample to be painted. If to < 0 the histogram will be painted to
           its last point.

       See also:
           setStyle(), style()

       Warning:
           The outline style requires, that the intervals are in increasing order and not
           overlapping.

   void QwtPlotHistogram::drawSeries (QPainter *painter, const QwtScaleMap &xMap, const
       QwtScaleMap &yMap, const QRectF &canvasRect, intfrom, intto) const [virtual] Draw a subset
       of the histogram samples
       Parameters:
           painter Painter
           xMap Maps x-values into pixel coordinates.
           yMap Maps y-values into pixel coordinates.
           canvasRect Contents rect of the canvas
           from Index of the first sample to be painted
           to Index of the last sample to be painted. If to < 0 the series will be painted to its
           last sample.

       See also:
           drawOutline(), drawLines(), drawColumns

       Implements QwtPlotAbstractSeriesItem.

   const QPen & QwtPlotHistogram::pen () const Returns:
           Pen used in a style() depending way.

       See also:
           setPen(), brush()

   int QwtPlotHistogram::rtti () const [virtual] Returns:
           QwtPlotItem::Rtti_PlotHistogram

       Reimplemented from QwtPlotItem.

   void QwtPlotHistogram::setBaseline (doublevalue)
       Set the value of the baseline. Each column representing an QwtIntervalSample is defined by
       its interval and the interval between baseline and the value of the sample.

       The default value of the baseline is 0.0.

       Parameters:
           value Value of the baseline

       See also:
           baseline()

   void QwtPlotHistogram::setBrush (const QBrush &brush) Assign a brush, that is used in a
       style() depending way.
       Parameters:
           brush New brush

       See also:
           pen(), brush()

   void QwtPlotHistogram::setPen (const QPen &pen) Assign a pen, that is used in a style()
       depending way.
       Parameters:
           pen New pen

       See also:
           pen(), brush()

   void QwtPlotHistogram::setSamples (const QVector< QwtIntervalSample > &samples) Initialize
       data with an array of samples.
       Parameters:
           samples Vector of points

   void QwtPlotHistogram::setStyle (HistogramStylestyle) Set the histogram's drawing style
       Parameters:
           style Histogram style

       See also:
           HistogramStyle, style()

   void QwtPlotHistogram::setSymbol (const QwtColumnSymbol *symbol)
       Assign a symbol. In Column style an optional symbol can be assigned, that is responsible
       for displaying the rectangle that is defined by the interval and the distance between
       baseline() and value. When no symbol has been defined the area is displayed as plain
       rectangle using pen() and brush().

       See also:
           style(), symbol(), drawColumn(), pen(), brush()

       Note:
           In applications, where different intervals need to be displayed in a different way (
           f.e different colors or even using differnt symbols) it is recommended to overload
           drawColumn().

   QwtPlotHistogram::HistogramStyle QwtPlotHistogram::style () const Return the current style
       See also:
           HistogramStyle, setStyle()

   const QwtColumnSymbol * QwtPlotHistogram::symbol () const Returns:
           Current symbol or NULL, when no symbol has been assigned

       See also:
           setSymbol()

Author

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