A class, which displays raster data. More...
#include <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 |
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.
The default policy is NoCache
QwtPlotRasterItem::QwtPlotRasterItem | ( | const QString & | title = QString::null |
) | [explicit] |
Constructor.
QwtPlotRasterItem::QwtPlotRasterItem | ( | const QwtText & | title | ) | [explicit] |
Constructor.
QwtPlotRasterItem::~QwtPlotRasterItem | ( | ) | [virtual] |
Destructor.
int QwtPlotRasterItem::alpha | ( | ) | const |
QwtPlotRasterItem::CachePolicy QwtPlotRasterItem::cachePolicy | ( | ) | const |
void QwtPlotRasterItem::draw | ( | QPainter * | painter, | |
const QwtScaleMap & | xMap, | |||
const QwtScaleMap & | yMap, | |||
const QRect & | canvasRect | |||
) | const [virtual] |
Draw the raster data.
painter | Painter | |
xMap | X-Scale Map | |
yMap | Y-Scale Map | |
canvasRect | Contents rect of the plot canvas |
Implements QwtPlotItem.
Reimplemented in QwtPlotSpectrogram.
void QwtPlotRasterItem::invalidateCache | ( | ) |
Invalidate the paint cache
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.
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
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.
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.
alpha | Alpha value |
The default alpha value is -1.
void QwtPlotRasterItem::setCachePolicy | ( | QwtPlotRasterItem::CachePolicy | policy | ) |
Change the cache policy
The default policy is NoCache
policy | Cache policy |