QwtPlotHistogram(3)

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, and QwtSeriesStore< 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 ()
Destructor.
virtual int rtti () const
void setPen (const QColor &, qreal width=0.0, Qt::PenStyle=Qt::SolidLine)
void setPen (const QPen &)
const QPen & pen () const
void setBrush (const QBrush &)
const QBrush & brush () const
void setSamples (const QVector< QwtIntervalSample > &)
void setSamples (QwtSeriesData< QwtIntervalSample > *)
void setBaseline (double reference)
Set the value of the baseline.
double baseline () const
void setStyle (HistogramStyle style)
HistogramStyle style () const
void setSymbol (const QwtColumnSymbol *)
Assign a symbol.
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 QwtGraphic legendIcon (int index, const QSizeF &) 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.

See also:
    QwtPlotBarChart, QwtPlotMultiBarChart

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.

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.

  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 different symbols) it is recommended to overload drawColumn().

  void QwtPlotHistogram::drawColumns (QPainter * painter, const QwtScaleMap & xMap, const QwtScaleMap & yMap, int from, int to) 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::drawLines (QPainter * painter, const QwtScaleMap & xMap, const QwtScaleMap & yMap, int from, int to) 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, int from, int to) 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, int from, int to) 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 rectangle 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 QwtPlotSeriesItem.

  QwtGraphic QwtPlotHistogram::legendIcon (int index, const QSizeF & size) const [virtual]
A plain rectangle without pen using the brush()

Parameters:
    index Index of the legend entry ( ignored as there is only one )
    size Icon size

Returns:
    A graphic displaying the icon

See also:
    QwtPlotItem::setLegendIconSize(), QwtPlotItem::legendData()

Reimplemented from QwtPlotItem.

  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 (double value)

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 QColor & color, qreal width = 0.0, Qt::PenStyle style = Qt::SolidLine)
Build and assign a pen

In Qt5 the default pen width is 1.0 ( 0.0 in Qt4 ) what makes it non cosmetic ( see QPen::isCosmetic() ). This method has been introduced to hide this incompatibility.

Parameters:
    color Pen color
    width Pen width
    style Pen style

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::setSamples (QwtSeriesData< QwtIntervalSample > * data)
Assign a series of samples

setSamples() is just a wrapper for setData() without any additional value - beside that it is easier to find for the developer.

Parameters:
    data Data

Warning:
    The item takes ownership of the data object, deleting it when its not used anymore.

  void QwtPlotHistogram::setStyle (HistogramStyle style)
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 different symbols) it is recommended to overload drawColumn().

  QwtPlotHistogram::HistogramStyle QwtPlotHistogram::style () const

Returns:
    Style of the histogram

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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