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

#include <qwt_plot_rasteritem.h>

Inheritance diagram for QwtPlotRasterItem:

Collaboration diagram for QwtPlotRasterItem:

Classes
class	PrivateData
Public Types
enum	CachePolicy { NoCache, PaintCache, ScreenCache }
Public Member Functions
	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.
Protected Member Functions
virtual QImage	renderImage (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QwtDoubleRect &area) const =0

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.

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

Enumerator:

NoCache
PaintCache
ScreenCache

Definition at line 56 of file qwt_plot_rasteritem.h.

    {
        NoCache,
        PaintCache,
        ScreenCache
    };

Constructor & Destructor Documentation

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

Constructor.

Definition at line 91 of file qwt_plot_rasteritem.cpp.

                                                        :
    QwtPlotItem(QwtText(title))
{
    init();
}

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

Constructor.

Definition at line 98 of file qwt_plot_rasteritem.cpp.

                                                        :
    QwtPlotItem(title)
{
    init();
}

QwtPlotRasterItem::~QwtPlotRasterItem ( ) [virtual]

Destructor.

Definition at line 105 of file qwt_plot_rasteritem.cpp.

{
    delete d_data;
}

Member Function Documentation

int QwtPlotRasterItem::alpha ( ) const

Returns:: Alpha value of the raster item

See also:: setAlpha()

Definition at line 163 of file qwt_plot_rasteritem.cpp.

References QwtPlotRasterItem::PrivateData::alpha.

Referenced by setAlpha().

{
    return d_data->alpha;
}

QwtPlotRasterItem::CachePolicy QwtPlotRasterItem::cachePolicy ( ) const

Returns:: Cache policy

See also:: CachePolicy, setCachePolicy()

Definition at line 192 of file qwt_plot_rasteritem.cpp.

References QwtPlotRasterItem::PrivateData::cache, and QwtPlotRasterItem::PrivateData::ImageCache::policy.

{
    return d_data->cache.policy;
}

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 QwtPlotRasterItem::PrivateData::alpha, QwtPlotItem::boundingRect(), QwtPlotRasterItem::PrivateData::cache, QwtPlotRasterItem::PrivateData::ImageCache::image, QwtPlotItem::invTransform(), NoCache, PaintCache, QwtPlotItem::paintRect(), QwtPlotRasterItem::PrivateData::ImageCache::policy, QwtPlotRasterItem::PrivateData::ImageCache::rect, renderImage(), ScreenCache, QwtScaleMap::setPaintInterval(), QwtPlotRasterItem::PrivateData::ImageCache::size, toRgba(), and QwtPlotItem::transform().

{
    if ( canvasRect.isEmpty() || d_data->alpha == 0 )
        return;

    QwtDoubleRect area = invTransform(xMap, yMap, canvasRect);
    if ( boundingRect().isValid() )
        area &= boundingRect();

    const QRect paintRect = transform(xMap, yMap, area);
    if ( !paintRect.isValid() )
        return;

    QImage image;

    bool doCache = true;
    if ( painter->device()->devType() == QInternal::Printer 
            || painter->device()->devType() == QInternal::Picture )
    {
        doCache = false;
    }

    if ( !doCache || d_data->cache.policy == NoCache )
    {
        image = renderImage(xMap, yMap, area);
        if ( d_data->alpha >= 0 && d_data->alpha < 255 )
            image = toRgba(image, d_data->alpha);

    }
    else if ( d_data->cache.policy == PaintCache )
    {
        if ( d_data->cache.image.isNull() || d_data->cache.rect != area
            || d_data->cache.size != paintRect.size() )
        {
            d_data->cache.image = renderImage(xMap, yMap, area);
            d_data->cache.rect = area;
            d_data->cache.size = paintRect.size();
        }

        image = d_data->cache.image;
        if ( d_data->alpha >= 0 && d_data->alpha < 255 )
            image = toRgba(image, d_data->alpha);
    }
    else if ( d_data->cache.policy == ScreenCache )
    {
        const QSize screenSize =
            QApplication::desktop()->screenGeometry().size();

        if ( paintRect.width() > screenSize.width() ||
            paintRect.height() > screenSize.height() )
        {
            image = renderImage(xMap, yMap, area);
        }
        else
        {
            if ( d_data->cache.image.isNull() || d_data->cache.rect != area )
            {
                QwtScaleMap cacheXMap = xMap;
                cacheXMap.setPaintInterval( 0, screenSize.width());

                QwtScaleMap cacheYMap = yMap;
                cacheYMap.setPaintInterval(screenSize.height(), 0);

                d_data->cache.image = renderImage(
                    cacheXMap, cacheYMap, area);
                d_data->cache.rect = area;
                d_data->cache.size = paintRect.size();
            }

            image = d_data->cache.image;
        }
        image = toRgba(image, d_data->alpha);
    }

    painter->drawImage(paintRect, image);
}

void QwtPlotRasterItem::invalidateCache ( )

Invalidate the paint cache

See also:: setCachePolicy()

Definition at line 201 of file qwt_plot_rasteritem.cpp.

References QwtPlotRasterItem::PrivateData::cache, QwtPlotRasterItem::PrivateData::ImageCache::image, QwtPlotRasterItem::PrivateData::ImageCache::rect, and QwtPlotRasterItem::PrivateData::ImageCache::size.

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

{
    d_data->cache.image = QImage();
    d_data->cache.rect = QwtDoubleRect();
    d_data->cache.size = QSize();
}

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.

{
    return QSize();
}

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().

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 alpha(), QwtPlotRasterItem::PrivateData::alpha, and QwtPlotItem::itemChanged().

{
    if ( alpha < 0 )
        alpha = -1;

    if ( alpha > 255 )
        alpha = 255;

    if ( alpha != d_data->alpha )
    {
        d_data->alpha = alpha;

        itemChanged();
    }
}

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 QwtPlotRasterItem::PrivateData::cache, invalidateCache(), QwtPlotItem::itemChanged(), and QwtPlotRasterItem::PrivateData::ImageCache::policy.

{
    if ( d_data->cache.policy != policy )
    {
        d_data->cache.policy = policy;

        invalidateCache();
        itemChanged();
    }
}

The documentation for this class was generated from the following files:

QwtPlotRasterItem Class Reference

Classes

Public Types

Public Member Functions

Protected Member Functions

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation