conflicting packages
QwtPlotRasterItem(3) | Qwt User's Guide | QwtPlotRasterItem(3) |
NAME¶
QwtPlotRasterItem - A class, which displays raster data.SYNOPSIS¶
#include <qwt_plot_rasteritem.h> Inherits QwtPlotItem. Inherited by QwtPlotSpectrogram.Public Types¶
enum CachePolicy { NoCache, PaintCache }
Public Member Functions¶
QwtPlotRasterItem (const QString &title=QString::null)
Protected Member Functions¶
virtual QImage renderImage (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &area, const QSize &imageSize) const =0
Detailed Description¶
A class, which displays raster data.QwtPlotSpectrogram
Member Typedef Documentation¶
typedef QFlags<PaintAttribute> QwtPlotRasterItem::PaintAttributes¶
Paint attributes.Member Enumeration Documentation¶
enum QwtPlotRasterItem::CachePolicy .IP • 2¶
NoCacherenderImage() 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.
enum QwtPlotRasterItem::PaintAttribute Attributes to modify the drawing algorithm.¶
See also:setPaintAttribute(),
testPaintAttribute()
- 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.
Constructor & Destructor Documentation¶
QwtPlotRasterItem::QwtPlotRasterItem (const QString &title = QString::null) [explicit]¶
Constructor.QwtPlotRasterItem::QwtPlotRasterItem (const QwtText &title) [explicit]¶
Constructor.QwtPlotRasterItem::~QwtPlotRasterItem () [virtual]¶
Destructor.Member Function Documentation¶
int QwtPlotRasterItem::alpha () const Returns:¶
Alpha value of the raster item
See also:
setAlpha()
QRectF QwtPlotRasterItem::boundingRect () const [virtual] Returns:¶
Bounding rect of the data
See also:
QwtPlotRasterItem::interval()
QwtPlotRasterItem::CachePolicy QwtPlotRasterItem::cachePolicy () const Returns:¶
Cache policy
See also:
CachePolicy,
setCachePolicy()
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 rect of the plot canvas
QwtScaleMap QwtPlotRasterItem::imageMap (Qt::Orientationorientation, const QwtScaleMap &map, const QRectF &area, const QSize &imageSize, doublepixelSize) 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
QwtInterval QwtPlotRasterItem::interval (Qt::Axisaxis) 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
void QwtPlotRasterItem::invalidateCache () Invalidate the paint cache¶
See also:setCachePolicy()
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 neighboured 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()
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
void QwtPlotRasterItem::setAlpha (intalpha)¶
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.
alpha()
void QwtPlotRasterItem::setCachePolicy (QwtPlotRasterItem::CachePolicypolicy) Change the cache policy¶
The default policy is NoCache Parameters:policy Cache policy
See also:
CachePolicy, cachePolicy()
void QwtPlotRasterItem::setPaintAttribute (PaintAttributeattribute, boolon = true) Specify an attribute how to draw the raster item¶
Parameters:attribute Paint attribute
on On/Off /sa PaintAttribute, testPaintAttribute()
bool QwtPlotRasterItem::testPaintAttribute (PaintAttributeattribute) const¶
Return the current paint attributes. See also:PaintAttribute,
setPaintAttribute()
Author¶
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