A class, which displays raster data. More...

#include <qwt_plot_rasteritem.h>

Inheritance diagram for QwtPlotRasterItem:

Classes
class	PrivateData

Public Types
enum	CachePolicy { NoCache , PaintCache }
	Cache policy. More...

enum	PaintAttribute { PaintInDeviceResolution = 1 }
	Paint attributes. More...

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_PlotArrowMarker , Rtti_PlotBoxChart , Rtti_PlotUserItem = 1000 }
	Runtime type information. More...

enum	ItemAttribute { Legend = 0x01 , AutoScale = 0x02 , Margins = 0x04 }
	Plot Item Attributes. More...

enum	ItemInterest { ScaleInterest = 0x01 , LegendInterest = 0x02 }
	Plot Item Interests. More...

enum	RenderHint { RenderAntialiased = 0x1 }
	Render hints. More...

Public Member Functions
	QwtPlotRasterItem (const QString &title=QString())
	Constructor.

	QwtPlotRasterItem (const QwtText &title)

void	setPaintAttribute (PaintAttribute, bool on=true)
	Set a paint attribute.

bool	testPaintAttribute (PaintAttribute) const
	Test a paint attribute.

void	setAlpha (int alpha)
	Set an alpha value for the raster data.

int	alpha () const
	Get the alpha value of the raster item.

void	setCachePolicy (CachePolicy)
	Change the cache policy.

CachePolicy	cachePolicy () const
	Get the cache policy.

void	invalidateCache ()
	Invalidate the paint cache.

virtual void	draw (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect) const override
	Draw the raster data.

virtual QRectF	pixelHint (const QRectF &) const
	Pixel hint.

virtual QwtInterval	interval (Qt::Axis) const
	Get the bounding interval for an axis.

virtual QRectF	boundingRect () const override
	Get the bounding rectangle of the data.

Public Member Functions inherited from QwtPlotItem
	QwtPlotItem ()
	Default constructor.

	QwtPlotItem (const QString &title)
	Constructor with title as QString.

	QwtPlotItem (const QwtText &title)
	Constructor with title as QwtText.

virtual	~QwtPlotItem ()
	Destructor.

virtual void	attach (QwtPlot *plot)
	Attach the item to a plot.

void	detach ()
	Detach the item from the plot.

QwtPlot *	plot () const
	Get the plot the item is attached to.

void	setTitle (const QString &title)
	Set the title using a QString.

void	setTitle (const QwtText &title)
	Set the title using a QwtText.

const QwtText &	title () const
	Get the title.

virtual int	rtti () const
	Runtime type information.

void	setItemAttribute (ItemAttribute, bool on=true)
	Set an item attribute.

bool	testItemAttribute (ItemAttribute) const
	Test an item attribute.

void	setItemInterest (ItemInterest, bool on=true)
	Set an item interest.

bool	testItemInterest (ItemInterest) const
	Test an item interest.

void	setRenderHint (RenderHint, bool on=true)
	Set a render hint.

bool	testRenderHint (RenderHint) const
	Test a render hint.

void	setRenderThreadCount (uint numThreads)
	Set the number of render threads.

uint	renderThreadCount () const
	Get the number of render threads.

void	setLegendIconSize (const QSize &)
	Set the legend icon size.

QSize	legendIconSize () const
	Get the legend icon size.

double	z () const
	Get the z-value.

void	setZ (double z)
	Set the z-value.

void	show ()
	Show the item.

void	hide ()
	Hide the item.

virtual void	setVisible (bool)
	Set the visibility.

bool	isVisible () const
	Check if the item is visible.

void	setAxes (QwtAxisId xAxis, QwtAxisId yAxis)
	Set both axes.

void	setXAxis (QwtAxisId)
	Set the x-axis.

QwtAxisId	xAxis () const
	Get the x-axis.

void	setYAxis (QwtAxisId)
	Set the y-axis.

QwtAxisId	yAxis () const
	Get the y-axis.

virtual void	itemChanged ()
	Notify the plot that the item has changed.

virtual void	legendChanged ()
	Notify the item that the legend has changed.

virtual void	getCanvasMarginHint (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect, double &left, double &top, double &right, double &bottom) const
	Get margin hints for the canvas.

virtual void	updateScaleDiv (const QwtScaleDiv &, const QwtScaleDiv &)
	Update the item with new scale divisions.

virtual void	updateLegend (const QwtPlotItem *, const QList< QwtLegendData > &)
	Update the item with changes of the legend.

QRectF	scaleRect (const QwtScaleMap &, const QwtScaleMap &) const
	Calculate the scale rectangle.

QRectF	paintRect (const QwtScaleMap &, const QwtScaleMap &) const
	Calculate the paint rectangle.

virtual QList< QwtLegendData >	legendData () const
	Return legend data.

virtual QwtGraphic	legendIcon (int index, const QSizeF &) const
	Return a legend icon.

Protected Member Functions
virtual QImage	renderImage (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &area, const QSize &imageSize) const =0

virtual QwtScaleMap	imageMap (Qt::Orientation, const QwtScaleMap &map, const QRectF &area, const QSize &imageSize, double pixelSize) const
	Get the image map.

Protected Member Functions inherited from QwtPlotItem
QwtGraphic	defaultIcon (const QBrush &, const QSizeF &) const
	Create a default icon.

Detailed Description

A class, which displays raster data.

Raster data is a grid of pixel values, that can be represented as a QImage. It is used for many types of information like spectrograms, cartograms, geographical maps ...

Often a plot has several types of raster data organized in layers. (e.g a geographical map, with weather statistics ). Using setAlpha() raster items can be stacked easily.

QwtPlotRasterItem is only implemented for images of the following formats: QImage::Format_Indexed8, QImage::Format_ARGB32.

See also: QwtPlotSpectrogram

Member Enumeration Documentation

◆ CachePolicy

enum QwtPlotRasterItem::CachePolicy

Cache policy.

The default policy is NoCache

Enumerator

NoCache

renderImage() is called each time the item has to be repainted

PaintCache

renderImage() is called, whenever the image cache is not valid, or the scales, or the size of the canvas has changed.

This type of cache is useful for improving the performance of hide/show operations or manipulations of the alpha value. All other situations are handled by the canvas backing store.

◆ PaintAttribute

enum QwtPlotRasterItem::PaintAttribute

Paint attributes.

Attributes to modify the drawing algorithm.

See also: setPaintAttribute(), testPaintAttribute()

Enumerator

PaintInDeviceResolution

When the image is rendered according to the data pixels ( QwtRasterData::pixelHint() ) it can be expanded to paint device resolution before it is passed to QPainter. The expansion algorithm rounds the pixel borders in the same way as the axis ticks, what is usually better than the scaling algorithm implemented in Qt. Disabling this flag might make sense, to reduce the size of a document/file. If this is possible for a document format depends on the implementation of the specific QPaintEngine.

Constructor & Destructor Documentation

◆ QwtPlotRasterItem()

QwtPlotRasterItem::QwtPlotRasterItem ( const QString & title = QString() )

explicit

Constructor.

Parameters

[in] title Title of the raster item

Constructor with title

Parameters

[in] title Title of the raster item

Destructor

Member Function Documentation

◆ alpha()

int QwtPlotRasterItem::alpha ( ) const

Get the alpha value of the raster item.

Returns: Alpha value of the raster item

See also: setAlpha()

◆ boundingRect()

QRectF QwtPlotRasterItem::boundingRect ( ) const

overridevirtual

Get the bounding rectangle of the data.

Returns: Bounding rectangle of the data

See also: QwtPlotRasterItem::interval()

Reimplemented from QwtPlotItem.

◆ cachePolicy()

QwtPlotRasterItem::CachePolicy QwtPlotRasterItem::cachePolicy ( ) const

Get the cache policy.

Returns: Cache policy

See also: CachePolicy, setCachePolicy()

◆ draw()

void QwtPlotRasterItem::draw	(	QPainter *	painter,
		const QwtScaleMap &	xMap,
		const QwtScaleMap &	yMap,
		const QRectF &	canvasRect
	)		const

overridevirtual

Draw the raster data.

Parameters

[in]	painter	Painter
[in]	xMap	X-Scale Map
[in]	yMap	Y-Scale Map
[in]	canvasRect	Contents rectangle of the plot canvas

Implements QwtPlotItem.

Reimplemented in QwtPlotSpectrogram.

◆ imageMap()

QwtScaleMap QwtPlotRasterItem::imageMap	(	Qt::Orientation	orientation,
		const QwtScaleMap &	map,
		const QRectF &	area,
		const QSize &	imageSize,
		double	pixelSize
	)		const

protectedvirtual

Get the image map.

Calculate a scale map for painting to an image.

Parameters

orientation	Orientation, Qt::Horizontal means a X axis
map	Scale map for rendering the plot item
area	Area to be painted on the image
imageSize	Image size
pixelSize	Width/Height of a data pixel

Returns: Calculated scale map

◆ interval()

QwtInterval QwtPlotRasterItem::interval ( Qt::Axis axis ) const

virtual

Get the bounding interval for an axis.

This method is intended to be reimplemented by derived classes. The default implementation returns an invalid interval.

Parameters

[in] axis X, Y, or Z axis

Returns: Bounding interval for an axis

Reimplemented in QwtPlotSpectrogram.

◆ invalidateCache()

void QwtPlotRasterItem::invalidateCache ( )

Invalidate the paint cache.

See also: setCachePolicy()

◆ pixelHint()

QRectF QwtPlotRasterItem::pixelHint ( const QRectF & area ) const

virtual

Pixel hint.

The geometry of a pixel is used to calculate the resolution and alignment of the rendered image. Width and height of the hint need to be the horizontal and vertical distances between 2 neighboring points. The center of the hint has to be the position of any point (it doesn't matter which one). Limiting the resolution of the image might significantly improve the performance and heavily reduce the amount of memory when rendering a QImage from the raster data. The default implementation returns an empty rectangle (QRectF()), meaning that the image will be rendered in target device (e.g. screen) resolution.

Parameters

[in] area In most implementations the resolution of the data doesn't depend on the requested area

Returns: Bounding rectangle of a pixel

See also: render(), renderImage()

Reimplemented in QwtPlotSpectrogram.

◆ renderImage()

virtual QImage QwtPlotRasterItem::renderImage	(	const QwtScaleMap &	xMap,
		const QwtScaleMap &	yMap,
		const QRectF &	area,
		const QSize &	imageSize
	)		const

protectedpure virtual

Implemented in QwtPlotSpectrogram.

◆ setAlpha()

void QwtPlotRasterItem::setAlpha ( int alpha )

Set an alpha value for the raster data.

Often a plot has several types of raster data organized in layers. (e.g. a geographical map, with weather statistics). Using setAlpha() raster items can be stacked easily. The alpha value is a value [0, 255] to control the transparency of the image. 0 represents a fully transparent color, while 255 represents a fully opaque color.

alpha >= 0: All alpha values of the pixels returned by renderImage() will be set to alpha, beside those with an alpha value of 0 (invalid pixels).
alpha < 0: The alpha values returned by renderImage() are not changed. The default alpha value is -1.
Parameters

[in] alpha Alpha value

See also
alpha()

◆ setCachePolicy()

void QwtPlotRasterItem::setCachePolicy ( QwtPlotRasterItem::CachePolicy policy )

Change the cache policy.

The default policy is NoCache

Parameters

[in] policy Cache policy

See also: CachePolicy, cachePolicy()

◆ setPaintAttribute()

void QwtPlotRasterItem::setPaintAttribute	(	PaintAttribute	attribute,
		bool	on = `true`
	)

Set a paint attribute.

Parameters

[in]	attribute	Paint attribute
[in]	on	On/Off

See also: PaintAttribute, testPaintAttribute()

◆ testPaintAttribute()

bool QwtPlotRasterItem::testPaintAttribute ( PaintAttribute attribute ) const

Test a paint attribute.

Parameters

[in] attribute Paint attribute

Returns: True, when attribute is enabled

See also: PaintAttribute, setPaintAttribute()

The documentation for this class was generated from the following files:

/home/runner/work/QWT/QWT/src/plot/qwt_plot_rasteritem.h
/home/runner/work/QWT/QWT/src/plot/qwt_plot_rasteritem.cpp

Classes

Public Types

Public Member Functions

Protected Member Functions

Detailed Description

Member Enumeration Documentation

◆ CachePolicy

◆ PaintAttribute

Constructor & Destructor Documentation

◆ QwtPlotRasterItem()

Member Function Documentation

◆ alpha()

◆ boundingRect()

◆ cachePolicy()

◆ draw()

◆ imageMap()

◆ interval()

◆ invalidateCache()

◆ pixelHint()

◆ renderImage()

◆ setAlpha()

◆ setCachePolicy()

◆ setPaintAttribute()

◆ testPaintAttribute()