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 The default policy is NoCache. More...

enum	PaintAttribute { PaintInDeviceResolution = 1 }
	Attributes to modify the drawing algorithm. 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_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/绘图项关注的事件类型 More...

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

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

	QwtPlotRasterItem (const QwtText &title)
	Constructor.

virtual	~QwtPlotRasterItem ()
	Destructor.

void	setPaintAttribute (PaintAttribute, bool on=true)
	Specify an attribute how to draw the raster item.

bool	testPaintAttribute (PaintAttribute) const

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

int	alpha () const

void	setCachePolicy (CachePolicy)
	Change the cache policy.

CachePolicy	cachePolicy () const

void	invalidateCache ()
	Invalidate the paint cache.

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

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

virtual QwtInterval	interval (Qt::Axis) const

virtual QRectF	boundingRect () const QWT_OVERRIDE

Public Member Functions inherited from QwtPlotItem
	QwtPlotItem ()
	Constructor.

	QwtPlotItem (const QString &title)
	Constructor.

	QwtPlotItem (const QwtText &title)
	Constructor.

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)
	Set a new title.

void	setTitle (const QwtText &title)
	Set a new title.

const QwtText &	title () const

virtual int	rtti () const
	Return rtti for the specific class represented.

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

bool	testItemAttribute (ItemAttribute) const
	Test an item attribute.

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

bool	testItemInterest (ItemInterest) const
	Test an item interest.

void	setRenderHint (RenderHint, bool on=true)
	Toggle an render hint.

bool	testRenderHint (RenderHint) const
	Test a render hint.

void	setRenderThreadCount (uint numThreads)
	On multi core systems rendering of certain plot item ( f.e QwtPlotRasterItem ) can be done in parallel in several threads.

uint	renderThreadCount () const

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

QSize	legendIconSize () const

double	z () const
	Plot items are painted in increasing z-order.

void	setZ (double z)
	Set the z value.

void	show ()
	Show the item.

void	hide ()
	Hide the item.

virtual void	setVisible (bool)
	Show/Hide the item.

bool	isVisible () const

void	setAxes (QwtAxisId xAxis, QwtAxisId yAxis)
	Set X and Y axis.

void	setXAxis (QwtAxisId)
	Set the X axis.

QwtAxisId	xAxis () const
	Return xAxis.

void	setYAxis (QwtAxisId)
	Set the Y axis.

QwtAxisId	yAxis () const
	Return yAxis.

virtual void	itemChanged ()
	Update the legend and call QwtPlot::autoRefresh() for the parent plot.

virtual void	legendChanged ()
	Update the legend of the parent plot.

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 =0
	Render an image.

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 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. ( f.e 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

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.

Member Function Documentation

◆ alpha()

int QwtPlotRasterItem::alpha ( ) const

Returns: Alpha value of the raster item

See also: setAlpha()

◆ boundingRect()

QRectF QwtPlotRasterItem::boundingRect ( ) const

virtual

Returns: Bounding rectangle of the data

See also: QwtPlotRasterItem::interval()

Reimplemented from QwtPlotItem.

◆ cachePolicy()

QwtPlotRasterItem::CachePolicy QwtPlotRasterItem::cachePolicy ( ) const

Returns: Cache policy

See also: CachePolicy, setCachePolicy()

◆ draw()

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

virtual

Draw the raster data.

Parameters

painter	Painter
xMap	X-Scale Map
yMap	Y-Scale Map
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

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

Returns: Bounding interval for an axis

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

Parameters

axis	X, Y, or Z 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 calculated the resolution and alignment of the rendered image.

Width and height of the hint need to be the horizontal and vertical distances between 2 neighbored 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 ( f.e screen ) resolution.

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: 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

Render an image.

An implementation of render() might iterate over all pixels of imageRect. Each pixel has to be translated into the corresponding position in scale coordinates using the maps. This position can be used to look up a value in a implementation specific way and to map it into a color.

Parameters

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

Returns: Rendered image

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. ( f.e 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.

Parameters

alpha Alpha value

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.

See also: alpha()

◆ setCachePolicy()

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

Change the cache policy.

The default policy is NoCache

Parameters

policy Cache policy

See also: CachePolicy, cachePolicy()

◆ setPaintAttribute()

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

Specify an attribute how to draw the raster item.

Parameters

attribute	Paint attribute
on	On/Off /sa PaintAttribute, testPaintAttribute()

◆ testPaintAttribute()

bool QwtPlotRasterItem::testPaintAttribute ( PaintAttribute attribute ) const

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

Classes

Public Types

Public Member Functions

Protected Member Functions

Detailed Description

Member Enumeration Documentation

◆ CachePolicy

◆ PaintAttribute

Member Function Documentation

◆ alpha()

◆ boundingRect()

◆ cachePolicy()

◆ draw()

◆ imageMap()

◆ interval()

◆ invalidateCache()

◆ pixelHint()

◆ renderImage()

◆ setAlpha()

◆ setCachePolicy()

◆ setPaintAttribute()

◆ testPaintAttribute()