Provided by: libqwt-doc_6.0.0-1.2_all 
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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