qwtplotrasteritem(3)
NAME
QwtPlotRasterItem
SYNOPSIS
Inherits QwtPlotItem. Inherited by QwtPlotSpectrogram.
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, constQwtScaleMap &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
- · 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
- 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
- · 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 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().
Author
- Generated automatically by Doxygen for Qwt User's Guide from the source
code.