Referencia de la Clase QwtPlotRasterItem

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

#include <qwt_plot_rasteritem.h>

Diagrama de herencias de QwtPlotRasterItem

Lista de todos los miembros.

Clases
class	PrivateData
Tipos públicos
enum	CachePolicy { NoCache, PaintCache, ScreenCache }
Métodos públicos
	QwtPlotRasterItem (const QString &title=QString::null)
	Constructor.
	QwtPlotRasterItem (const QwtText &title)
	Constructor.
virtual	~QwtPlotRasterItem ()
	Destructor.
void	setAlpha (int alpha)
	Set an alpha value for the raster data.
int	alpha () const
void	setCachePolicy (CachePolicy)
CachePolicy	cachePolicy () const
void	invalidateCache ()
virtual void	draw (QPainter *p, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRect &rect) const
	Draw the raster data.
virtual QSize	rasterHint (const QwtDoubleRect &) const
	Returns the recommended raster for a given rect.
Métodos protegidos
virtual QImage	renderImage (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QwtDoubleRect &area) const =0

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Descripción detallada

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.

Ver también:

QwtPlotSpectrogram

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Documentación de las enumeraciones miembro de la clase

enum QwtPlotRasterItem::CachePolicy

• NoCache
  renderImage() is called, whenever 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 only useful for improving the performance of hide/show operations. All other situations are already handled by the plot canvas cache.
• ScreenCache
  The screen cache is an image in size of the screen. As long as the scales don't change the target image is scaled from the cache. This might improve the performance when resizing the plot widget, but suffers from scaling effects.

The default policy is NoCache

Valores de enumeraciones:

NoCache
PaintCache
ScreenCache

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Documentación del constructor y destructor

QwtPlotRasterItem::QwtPlotRasterItem

(

const QString &

title = QString::null

)

[explicit]

Constructor.

QwtPlotRasterItem::QwtPlotRasterItem

(

const QwtText &

title

)

[explicit]

Constructor.

QwtPlotRasterItem::~QwtPlotRasterItem

(

)

[virtual]

Destructor.

---

Documentación de las funciones miembro

int QwtPlotRasterItem::alpha

(

)

const

Devuelve:

Alpha value of the raster item

Ver también:

setAlpha()

QwtPlotRasterItem::CachePolicy QwtPlotRasterItem::cachePolicy

(

)

const

Devuelve:

Cache policy

Ver también:

CachePolicy, setCachePolicy()

void QwtPlotRasterItem::draw	(	QPainter *	painter,
		const QwtScaleMap &	xMap,
		const QwtScaleMap &	yMap,
		const QRect &	canvasRect
	)		const [virtual]

Draw the raster data.

Parámetros:

painter	Painter
xMap	X-Scale Map
yMap	Y-Scale Map
canvasRect	Contents rect of the plot canvas

Implementa QwtPlotItem.

Reimplementado en QwtPlotSpectrogram.

void QwtPlotRasterItem::invalidateCache

(

)

Invalidate the paint cache

Ver también:

setCachePolicy

QSize QwtPlotRasterItem::rasterHint

(

const QwtDoubleRect &

)

const [virtual]

Returns the recommended raster for a given rect.

F.e the raster hint can be used to limit the resolution of the image that is rendered.

The default implementation returns an invalid size (QSize()), what means: no hint.

Reimplementado en QwtPlotSpectrogram.

virtual QImage QwtPlotRasterItem::renderImage	(	const QwtScaleMap &	xMap,
		const QwtScaleMap &	yMap,
		const QwtDoubleRect &	area
	)		const [protected, pure virtual]

Renders an image for an area

The format of the image must be QImage::Format_Indexed8, QImage::Format_RGB32 or QImage::Format_ARGB32

Parámetros:

xMap	Maps x-values into pixel coordinates.
yMap	Maps y-values into pixel coordinates.
area	Requested area for the image in scale coordinates

Implementado en 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.

Parámetros:

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.

Ver también:

alpha()

void QwtPlotRasterItem::setCachePolicy

(

QwtPlotRasterItem::CachePolicy

policy

)

Change the cache policy

The default policy is NoCache

Parámetros:

policy

Cache policy

Ver también:

CachePolicy, cachePolicy()

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La documentación para esta clase fue generada a partir de los siguientes ficheros:

• src/qwt/src/qwt_plot_rasteritem.h
• src/qwt/src/qwt_plot_rasteritem.cpp