QwtPlotRasterItem Class Reference

Inheritance diagram for QwtPlotRasterItem:

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Collaboration diagram for QwtPlotRasterItem:

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List of all members.

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 36 of file qwt_plot_rasteritem.h.

Public Types

enum  CachePolicy {
  NoCache,
  PaintCache,
  ScreenCache
}

Public Member Functions

 QwtPlotRasterItem (const QString &title=QString::null)
 QwtPlotRasterItem (const QwtText &title)
virtual ~QwtPlotRasterItem ()
void setAlpha (int alpha)
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
virtual QSize rasterHint (const QwtDoubleRect &) const

Protected Member Functions

virtual QImage renderImage (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QwtDoubleRect &area) const=0


Member Enumeration Documentation

enum QwtPlotRasterItem::CachePolicy

The default policy is NoCache

Definition at line 56 of file qwt_plot_rasteritem.h.


Constructor & Destructor Documentation

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

Constructor.

Definition at line 91 of file qwt_plot_rasteritem.cpp.

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

Constructor.

Definition at line 98 of file qwt_plot_rasteritem.cpp.

QwtPlotRasterItem::~QwtPlotRasterItem (  )  [virtual]

Destructor.

Definition at line 105 of file qwt_plot_rasteritem.cpp.


Member Function Documentation

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

The default alpha value is -1.

See also:
alpha()

Definition at line 143 of file qwt_plot_rasteritem.cpp.

References QwtPlotItem::itemChanged().

int QwtPlotRasterItem::alpha (  )  const

Returns:
Alpha value of the raster item
See also:
setAlpha()

Definition at line 163 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 176 of file qwt_plot_rasteritem.cpp.

References invalidateCache(), and QwtPlotItem::itemChanged().

QwtPlotRasterItem::CachePolicy QwtPlotRasterItem::cachePolicy (  )  const

Returns:
Cache policy
See also:
CachePolicy, setCachePolicy()

Definition at line 192 of file qwt_plot_rasteritem.cpp.

void QwtPlotRasterItem::invalidateCache (  ) 

Invalidate the paint cache

See also:
setCachePolicy

Definition at line 201 of file qwt_plot_rasteritem.cpp.

Referenced by setCachePolicy(), QwtPlotSpectrogram::setColorMap(), and QwtPlotSpectrogram::setData().

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

Draw the raster data.

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

Implements QwtPlotItem.

Reimplemented in QwtPlotSpectrogram.

Definition at line 229 of file qwt_plot_rasteritem.cpp.

References QwtPlotItem::boundingRect(), QwtPlotItem::invTransform(), QwtPlotItem::paintRect(), renderImage(), QwtScaleMap::setPaintInterval(), and QwtPlotItem::transform().

Referenced by QwtPlotSpectrogram::draw().

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.

Reimplemented in QwtPlotSpectrogram.

Definition at line 217 of file qwt_plot_rasteritem.cpp.

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

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

Implemented in QwtPlotSpectrogram.

Referenced by draw().


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