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 }
typedef QFlags< PaintAttribute >	PaintAttributes
	Paint attributes.
Public Member Functions
int	alpha () const
virtual QRectF	boundingRect () const
CachePolicy	cachePolicy () const
virtual void	draw (QPainter *p, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &rect) const
	Draw the raster data.
virtual QwtInterval	interval (Qt::Axis) const
void	invalidateCache ()
virtual QRectF	pixelHint (const QRectF &) const
	Pixel hint.
	QwtPlotRasterItem (const QString &title=QString::null)
	Constructor.
	QwtPlotRasterItem (const QwtText &title)
	Constructor.
void	setAlpha (int alpha)
	Set an alpha value for the raster data.
void	setCachePolicy (CachePolicy)
void	setPaintAttribute (PaintAttribute, bool on=true)
bool	testPaintAttribute (PaintAttribute) const
virtual	~QwtPlotRasterItem ()
	Destructor.
Protected Member Functions
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.
virtual QImage	renderImage (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &area, const QSize &imageSize) const =0
	Render an image.
Private Member Functions
QImage	compose (const QwtScaleMap &, const QwtScaleMap &, const QRectF &imageArea, const QRectF &paintRect, const QSize &imageSize, bool doCache) const
void	init ()
QwtPlotRasterItem &	operator= (const QwtPlotRasterItem &)
	QwtPlotRasterItem (const QwtPlotRasterItem &)
Private Attributes
PrivateData *	d_data

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

Definition at line 37 of file qwt_plot_rasteritem.h.

Member Typedef Documentation

typedef QFlags<PaintAttribute> QwtPlotRasterItem::PaintAttributes

Paint attributes.

Definition at line 84 of file qwt_plot_rasteritem.h.

Member Enumeration Documentation

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.

Definition at line 44 of file qwt_plot_rasteritem.h.

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.

Definition at line 66 of file qwt_plot_rasteritem.h.

Constructor & Destructor Documentation

QwtPlotRasterItem::QwtPlotRasterItem ( const QString & title = QString::null ) [explicit]

Constructor.

Definition at line 428 of file qwt_plot_rasteritem.cpp.

QwtPlotRasterItem::QwtPlotRasterItem ( const QwtText & title ) [explicit]

Constructor.

Definition at line 435 of file qwt_plot_rasteritem.cpp.

QwtPlotRasterItem::~QwtPlotRasterItem ( ) [virtual]

Destructor.

Definition at line 442 of file qwt_plot_rasteritem.cpp.

QwtPlotRasterItem::QwtPlotRasterItem ( const QwtPlotRasterItem & ) [explicit, private]

Member Function Documentation

int QwtPlotRasterItem::alpha ( ) const

Returns:: Alpha value of the raster item

See also:: setAlpha()

Definition at line 524 of file qwt_plot_rasteritem.cpp.

QRectF QwtPlotRasterItem::boundingRect ( ) const [virtual]

Returns:: Bounding rectangle of the data

See also:: QwtPlotRasterItem::interval()

Reimplemented from QwtPlotItem.

Definition at line 782 of file qwt_plot_rasteritem.cpp.

QwtPlotRasterItem::CachePolicy QwtPlotRasterItem::cachePolicy ( ) const

Returns:: Cache policy

See also:: CachePolicy, setCachePolicy()

Definition at line 553 of file qwt_plot_rasteritem.cpp.

QImage QwtPlotRasterItem::compose	(	const QwtScaleMap &	xMap,
		const QwtScaleMap &	yMap,
		const QRectF &	imageArea,
		const QRectF &	paintRect,
		const QSize &	imageSize,
		bool	doCache
	)		const `[private]`

Definition at line 817 of file qwt_plot_rasteritem.cpp.

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.

Definition at line 608 of file qwt_plot_rasteritem.cpp.

QwtScaleMap QwtPlotRasterItem::imageMap	(	Qt::Orientation	orientation,
		const QwtScaleMap &	map,
		const QRectF &	area,
		const QSize &	imageSize,
		double	pixelSize
	)		const `[protected, virtual]`

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

Definition at line 915 of file qwt_plot_rasteritem.cpp.

void QwtPlotRasterItem::init ( ) [private]

Definition at line 447 of file qwt_plot_rasteritem.cpp.

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.

Definition at line 772 of file qwt_plot_rasteritem.cpp.

void QwtPlotRasterItem::invalidateCache ( )

Invalidate the paint cache

See also:: setCachePolicy()

Definition at line 562 of file qwt_plot_rasteritem.cpp.

QwtPlotRasterItem& QwtPlotRasterItem::operator= ( const QwtPlotRasterItem & ) [private]

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.

Definition at line 595 of file qwt_plot_rasteritem.cpp.

virtual QImage QwtPlotRasterItem::renderImage	(	const QwtScaleMap &	xMap,
		const QwtScaleMap &	yMap,
		const QRectF &	area,
		const QSize &	imageSize
	)		const `[protected, pure 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.

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()

Definition at line 504 of file qwt_plot_rasteritem.cpp.

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

Change the cache policy

The default policy is NoCache

Parameters:

policy Cache policy

See also:: CachePolicy, cachePolicy()

Definition at line 537 of file qwt_plot_rasteritem.cpp.

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()

Definition at line 464 of file qwt_plot_rasteritem.cpp.

bool QwtPlotRasterItem::testPaintAttribute ( PaintAttribute attribute ) const

Returns:: True, when attribute is enabled

See also:: PaintAttribute, setPaintAttribute()

Definition at line 476 of file qwt_plot_rasteritem.cpp.

Member Data Documentation

PrivateData* QwtPlotRasterItem::d_data [private]

Reimplemented from QwtPlotItem.

Reimplemented in QwtPlotSpectrogram.

Definition at line 146 of file qwt_plot_rasteritem.h.

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

Classes

Public Types

Public Member Functions

Protected Member Functions

Private Member Functions

Private Attributes

Detailed Description

Member Typedef Documentation

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation