QwtPlotSpectrogram - A plot item, which displays a spectrogram.

NAME

QwtPlotSpectrogram − A plot item, which displays a spectrogram.

SYNOPSIS

#include <qwt_plot_spectrogram.h>

Inherits QwtPlotRasterItem.

Public Types

enum DisplayMode { ImageMode = 0x01, ContourMode = 0x02 }
typedef QFlags< DisplayMode > DisplayModes

Public Types inherited from QwtPlotRasterItem

enum CachePolicy { NoCache, PaintCache }
Cache policy The default policy is NoCache.
enum PaintAttribute { PaintInDeviceResolution = 1 }
typedef QFlags< PaintAttribute > PaintAttributes

Public Types inherited from QwtPlotItem

enum RttiValues { Rtti_PlotItem = 0, Rtti_PlotGrid, Rtti_PlotScale, Rtti_PlotLegend, Rtti_PlotMarker, Rtti_PlotCurve, Rtti_PlotSpectroCurve, Rtti_PlotIntervalCurve, Rtti_PlotHistogram, Rtti_PlotSpectrogram, Rtti_PlotGraphic, Rtti_PlotTradingCurve, Rtti_PlotBarChart, Rtti_PlotMultiBarChart, Rtti_PlotShape, Rtti_PlotTextLabel, Rtti_PlotZone, Rtti_PlotVectorField, Rtti_PlotUserItem = 1000 }
Runtime type information.
enum ItemAttribute { Legend = 0x01, AutoScale = 0x02, Margins = 0x04 }
Plot Item Attributes.
enum ItemInterest { ScaleInterest = 0x01, LegendInterest = 0x02 }
Plot Item Interests.
enum RenderHint { RenderAntialiased = 0x1 }
Render hints.
typedef QFlags< ItemAttribute > ItemAttributes
typedef QFlags< ItemInterest > ItemInterests
typedef QFlags< RenderHint > RenderHints

Public Member Functions

QwtPlotSpectrogram (const QString &title=QString())
virtual ˜QwtPlotSpectrogram ()
Destructor.
void setDisplayMode (DisplayMode, bool on=true)
bool testDisplayMode (DisplayMode) const
void setData (QwtRasterData *data)
const QwtRasterData * data () const
QwtRasterData * data ()
void setColorMap (QwtColorMap *)
const QwtColorMap * colorMap () const
void setColorTableSize (int numColors)
int colorTableSize () const
virtual QwtInterval interval (Qt::Axis) const override
virtual QRectF pixelHint (const QRectF &) const override
Pixel hint.
void setDefaultContourPen (const QColor &, qreal width=0.0, Qt::PenStyle=Qt::SolidLine)
void setDefaultContourPen (const QPen &)
Set the default pen for the contour lines.
QPen defaultContourPen () const
virtual QPen contourPen (double level) const
Calculate the pen for a contour line.
void setConrecFlag (QwtRasterData::ConrecFlag, bool on)
bool testConrecFlag (QwtRasterData::ConrecFlag) const
void setContourLevels (const QList< double > &)
QList< double > contourLevels () const
virtual int rtti () const override
virtual void draw (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect) const override
Draw the spectrogram.

Public Member Functions inherited from QwtPlotRasterItem

QwtPlotRasterItem (const QString &title=QString())
Constructor.
QwtPlotRasterItem (const QwtText &title)
Constructor.
virtual ˜QwtPlotRasterItem ()
Destructor.
void setPaintAttribute (PaintAttribute, bool on=true)
bool testPaintAttribute (PaintAttribute) const
void setAlpha (int alpha)
Set an alpha value for the raster data.
int alpha () const
void setCachePolicy (CachePolicy)
CachePolicy cachePolicy () const
void invalidateCache ()
virtual QRectF boundingRect () const override

Public Member Functions inherited from QwtPlotItem

QwtPlotItem ()
QwtPlotItem (const QString &title)
QwtPlotItem (const QwtText &title)
virtual ˜QwtPlotItem ()
Destroy the QwtPlotItem.
void attach (QwtPlot *plot)
Attach the item to a plot.
void detach ()
This method detaches a QwtPlotItem from any QwtPlot it has been associated with.
QwtPlot * plot () const
Return attached plot.
void setTitle (const QString &title)
void setTitle (const QwtText &title)
const QwtText & title () const
void setItemAttribute (ItemAttribute, bool on=true)
bool testItemAttribute (ItemAttribute) const
void setItemInterest (ItemInterest, bool on=true)
bool testItemInterest (ItemInterest) const
void setRenderHint (RenderHint, bool on=true)
bool testRenderHint (RenderHint) const
void setRenderThreadCount (uint numThreads)
uint renderThreadCount () const
void setLegendIconSize (const QSize &)
QSize legendIconSize () const
double z () const
void setZ (double z)
Set the z value.
void show ()
Show the item.
void hide ()
Hide the item.
virtual void setVisible (bool)
bool isVisible () const
void setAxes (QwtAxisId xAxis, QwtAxisId yAxis)
void setXAxis (QwtAxisId)
QwtAxisId xAxis () const
Return xAxis.
void setYAxis (QwtAxisId)
QwtAxisId yAxis () const
Return yAxis.
virtual void itemChanged ()
virtual void legendChanged ()
virtual void getCanvasMarginHint (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect, double &left, double &top, double &right, double &bottom) const
Calculate a hint for the canvas margin.
virtual void updateScaleDiv (const QwtScaleDiv &, const QwtScaleDiv &)
Update the item to changes of the axes scale division.
virtual void updateLegend (const QwtPlotItem *, const QList< QwtLegendData > &)
Update the item to changes of the legend info.
QRectF scaleRect (const QwtScaleMap &, const QwtScaleMap &) const
Calculate the bounding scale rectangle of 2 maps.
QRectF paintRect (const QwtScaleMap &, const QwtScaleMap &) const
Calculate the bounding paint rectangle of 2 maps.
virtual QList< QwtLegendData > legendData () const
Return all information, that is needed to represent the item on the legend.
virtual QwtGraphic legendIcon (int index, const QSizeF &) const

Protected Member Functions

virtual QImage renderImage (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &area, const QSize &imageSize) const override
Render an image from data and color map.
virtual QSize contourRasterSize (const QRectF &, const QRect &) const
Return the raster to be used by the CONREC contour algorithm.
virtual QwtRasterData::ContourLines renderContourLines (const QRectF &rect, const QSize &raster) const
virtual void drawContourLines (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QwtRasterData::ContourLines &) const
void renderTile (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRect &tile, QImage *) const
Render a tile of an image.

Protected Member Functions inherited from QwtPlotRasterItem

virtual QwtScaleMap imageMap (Qt::Orientation, const QwtScaleMap &map, const QRectF &area, const QSize &imageSize, double pixelSize) const
Calculate a scale map for painting to an image.

Protected Member Functions inherited from QwtPlotItem

QwtGraphic defaultIcon (const QBrush &, const QSizeF &) const
Return a default icon from a brush.

Detailed Description

A plot item, which displays a spectrogram.

A spectrogram displays 3-dimensional data, where the 3rd dimension ( the intensity ) is displayed using colors. The colors are calculated from the values using a color map.

On multi-core systems the performance of the image composition can often be improved by dividing the area into tiles - each of them rendered in a different thread ( see QwtPlotItem::setRenderThreadCount() ).

In ContourMode contour lines are painted for the contour levels.

See also

QwtRasterData, QwtColorMap, QwtPlotItem::setRenderThreadCount()

Definition at line 36 of file qwt_plot_spectrogram.h.

Member Typedef Documentation

typedef QFlags<DisplayMode > QwtPlotSpectrogram::DisplayModes

An ORed combination of DisplayMode values.

Definition at line 53 of file qwt_plot_spectrogram.h.

Member Enumeration Documentation

enum QwtPlotSpectrogram::DisplayMode

The display mode controls how the raster data will be represented.

See also

setDisplayMode(), testDisplayMode()

Enumerator
ImageMode

The values are mapped to colors using a color map.

ContourMode

The data is displayed using contour lines.

Definition at line 44 of file qwt_plot_spectrogram.h.

Constructor & Destructor Documentation

QwtPlotSpectrogram::QwtPlotSpectrogram (const QString & title = QString())[explicit]

Sets the following item attributes:

	•		QwtPlotItem::AutoScale: true
	•		QwtPlotItem::Legend: false

The z value is initialized by 8.0.

Parameters

title Title

See also

QwtPlotItem::setItemAttribute(), QwtPlotItem::setZ()

Definition at line 108 of file qwt_plot_spectrogram.cpp.

QwtPlotSpectrogram::˜QwtPlotSpectrogram () [virtual]

Destructor.

Definition at line 120 of file qwt_plot_spectrogram.cpp.

Member Function Documentation

const QwtColorMap * QwtPlotSpectrogram::colorMap () const

Returns

Color Map used for mapping the intensity values to colors

See also

setColorMap()

Definition at line 200 of file qwt_plot_spectrogram.cpp.

int QwtPlotSpectrogram::colorTableSize () const

Returns

Size of the color table, 0 means not using a color table

See also

QwtColorMap::colorTable(), setColorTableSize()

Definition at line 238 of file qwt_plot_spectrogram.cpp.

QList< double > QwtPlotSpectrogram::contourLevels () const

Returns

Levels of the contour lines.

The levels are sorted in increasing order.

See also

contourLevels(), renderContourLines(), QwtRasterData::contourLines()

Definition at line 382 of file qwt_plot_spectrogram.cpp.

QPen QwtPlotSpectrogram::contourPen (double level) const [virtual]

Calculate the pen for a contour line. The color of the pen is the color for level calculated by the color map

Parameters

level Contour level

Returns

Pen for the contour line

Note

contourPen is only used if defaultContourPen().style() == Qt::NoPen

See also

setDefaultContourPen(), setColorMap(), setContourLevels()

Definition at line 303 of file qwt_plot_spectrogram.cpp.

QSize QwtPlotSpectrogram::contourRasterSize (const QRectF & area, constQRect & rect) const [protected], [virtual]

Return the raster to be used by the CONREC contour algorithm. A larger size will improve the precision of the CONREC algorithm, but will slow down the time that is needed to calculate the lines.

The default implementation returns rect.size() / 2 bounded to the resolution depending on pixelSize().

Parameters

area Rectangle, where to calculate the contour lines
rect Rectangle in pixel coordinates, where to paint the contour lines

Returns

Raster to be used by the CONREC contour algorithm.

Note

The size will be bounded to rect.size().

See also

drawContourLines(), QwtRasterData::contourLines()

Definition at line 663 of file qwt_plot_spectrogram.cpp.

QwtRasterData * QwtPlotSpectrogram::data ()

Returns

Spectrogram data

See also

setData()

Definition at line 418 of file qwt_plot_spectrogram.cpp.

const QwtRasterData * QwtPlotSpectrogram::data () const

Returns

Spectrogram data

See also

setData()

Definition at line 409 of file qwt_plot_spectrogram.cpp.

QPen QwtPlotSpectrogram::defaultContourPen () const

Returns

Default contour pen

See also

setDefaultContourPen()

Definition at line 287 of file qwt_plot_spectrogram.cpp.

void QwtPlotSpectrogram::draw (QPainter * painter, const QwtScaleMap &xMap, const QwtScaleMap & yMap, const QRectF & canvasRect) const[override], [virtual]

Draw the spectrogram.

Parameters

painter Painter
xMap Maps x-values into pixel coordinates.
yMap Maps y-values into pixel coordinates.
canvasRect Contents rectangle of the canvas in painter coordinates

See also

setDisplayMode(), renderImage(), QwtPlotRasterItem::draw(), drawContourLines()

Reimplemented from QwtPlotRasterItem.

Definition at line 754 of file qwt_plot_spectrogram.cpp.

void QwtPlotSpectrogram::drawContourLines (QPainter * painter, constQwtScaleMap & xMap, const QwtScaleMap & yMap, constQwtRasterData::ContourLines & contourLines) const [protected],[virtual]

Paint the contour lines

Parameters

painter Painter
xMap Maps x-values into pixel coordinates.
yMap Maps y-values into pixel coordinates.
contourLines Contour lines

See also

renderContourLines(), defaultContourPen(), contourPen()

Definition at line 709 of file qwt_plot_spectrogram.cpp.

QwtInterval QwtPlotSpectrogram::interval (Qt::Axis axis) const [override],[virtual]

Returns

Bounding interval for an axis

The default implementation returns the interval of the associated raster data object.

Parameters

axis X, Y, or Z axis

See also

QwtRasterData::interval()

Reimplemented from QwtPlotRasterItem.

Definition at line 432 of file qwt_plot_spectrogram.cpp.

QRectF QwtPlotSpectrogram::pixelHint (const QRectF & area) const[override], [virtual]

Pixel hint. The geometry of a pixel is used to calculated the resolution and alignment of the rendered image.

The default implementation returns data()->pixelHint( rect );

Parameters

area In most implementations the resolution of the data doesn’t depend on the requested area.

Returns

Bounding rectangle of a pixel

See also

QwtPlotRasterItem::pixelHint(), QwtRasterData::pixelHint(), render(), renderImage()

Reimplemented from QwtPlotRasterItem.

Definition at line 456 of file qwt_plot_spectrogram.cpp.

QwtRasterData::ContourLines QwtPlotSpectrogram::renderContourLines (constQRectF & rect, const QSize & raster) const [protected], [virtual]

Calculate contour lines

Parameters

rect Rectangle, where to calculate the contour lines
raster Raster, used by the CONREC algorithm

Returns

Calculated contour lines

See also

contourLevels(), setConrecFlag(), QwtRasterData::contourLines()

Definition at line 689 of file qwt_plot_spectrogram.cpp.

QImage QwtPlotSpectrogram::renderImage (const QwtScaleMap & xMap, constQwtScaleMap & yMap, const QRectF & area, const QSize & imageSize) const[override], [protected], [virtual]

Render an image from data and color map. For each pixel of area the value is mapped into a color.

Parameters

xMap X-Scale Map
yMap Y-Scale Map
area Requested area for the image in scale coordinates
imageSize Size of the requested image

Returns

A QImage::Format_Indexed8 or QImage::Format_ARGB32 depending on the color map.

See also

QwtRasterData::value(), QwtColorMap::rgb(), QwtColorMap::colorIndex()

Implements QwtPlotRasterItem.

Definition at line 480 of file qwt_plot_spectrogram.cpp.

void QwtPlotSpectrogram::renderTile (const QwtScaleMap & xMap, constQwtScaleMap & yMap, const QRect & tile, QImage * image) const[protected]

Render a tile of an image. Rendering in tiles can be used to composite an image in parallel threads.

Parameters

xMap X-Scale Map
yMap Y-Scale Map
tile Geometry of the tile in image coordinates
image Image to be rendered

Definition at line 572 of file qwt_plot_spectrogram.cpp.

int QwtPlotSpectrogram::rtti () const [override], [virtual]

Returns

QwtPlotItem::Rtti_PlotSpectrogram

Reimplemented from QwtPlotItem.

Definition at line 126 of file qwt_plot_spectrogram.cpp.

void QwtPlotSpectrogram::setColorMap (QwtColorMap * colorMap)

Change the color map

Often it is useful to display the mapping between intensities and colors as an additional plot axis, showing a color bar.

Parameters

colorMap Color Map

See also

colorMap(), QwtScaleWidget::setColorBarEnabled(), QwtScaleWidget::setColorMap()

Definition at line 177 of file qwt_plot_spectrogram.cpp.

void QwtPlotSpectrogram::setColorTableSize (int numColors)

Limit the number of colors being used by the color map

When using a color table the mapping from the value into a color is usually faster as it can be done by simple lookups into a precalculated color table.

Setting a table size > 0 enables using a color table, while setting the size to 0 disables it.

The default size = 0, and no color table is used.

Parameters

numColors Number of colors. 0 means not using a color table

Note

The colorTableSize has no effect when using a color table of QwtColorMap::Indexed, where the size is always 256.

See also

QwtColorMap::colorTable(), colorTableSize()

Definition at line 224 of file qwt_plot_spectrogram.cpp.

void QwtPlotSpectrogram::setConrecFlag (QwtRasterData::ConrecFlag flag,bool on)

Modify an attribute of the CONREC algorithm, used to calculate the contour lines.

Parameters

flag CONREC flag
on On/Off

See also

testConrecFlag(), renderContourLines(), QwtRasterData::contourLines()

Definition at line 324 of file qwt_plot_spectrogram.cpp.

void QwtPlotSpectrogram::setContourLevels (const QList< double > & levels)

Set the levels of the contour lines

Parameters

levels Values of the contour levels

See also

contourLevels(), renderContourLines(), QwtRasterData::contourLines()

Note

contourLevels returns the same levels but sorted.

Definition at line 365 of file qwt_plot_spectrogram.cpp.

void QwtPlotSpectrogram::setData (QwtRasterData * data)

Set the data to be displayed

Parameters

data Spectrogram Data

See also

data()

Definition at line 393 of file qwt_plot_spectrogram.cpp.

void QwtPlotSpectrogram::setDefaultContourPen (const QColor & color, qrealwidth = 0.0, Qt::PenStyle style = Qt::SolidLine)

Build and assign the default pen for the contour lines

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()

Definition at line 256 of file qwt_plot_spectrogram.cpp.

void QwtPlotSpectrogram::setDefaultContourPen (const QPen & pen)

Set the default pen for the contour lines. If the spectrogram has a valid default contour pen a contour line is painted using the default contour pen. Otherwise (pen.style() == Qt::NoPen) the pen is calculated for each contour level using contourPen().

See also

defaultContourPen(), contourPen()

Definition at line 272 of file qwt_plot_spectrogram.cpp.

void QwtPlotSpectrogram::setDisplayMode (DisplayMode mode, bool on = true)

The display mode controls how the raster data will be represented.

Parameters

mode Display mode
on On/Off

The default setting enables ImageMode.

See also

DisplayMode, displayMode()

Definition at line 141 of file qwt_plot_spectrogram.cpp.

bool QwtPlotSpectrogram::testConrecFlag (QwtRasterData::ConrecFlag flag)const

Test an attribute of the CONREC algorithm, used to calculate the contour lines.

Parameters

flag CONREC flag

Returns

true, is enabled

The default setting enables QwtRasterData::IgnoreAllVerticesOnLevel

See also

setConrecClag(), renderContourLines(), QwtRasterData::contourLines()

Definition at line 350 of file qwt_plot_spectrogram.cpp.

bool QwtPlotSpectrogram::testDisplayMode (DisplayMode mode) const

The display mode controls how the raster data will be represented.

Parameters

mode Display mode

Returns

true if mode is enabled

Definition at line 161 of file qwt_plot_spectrogram.cpp.

Author

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Updated 2026-06-01 - jenkler.se | uex.se