QwtColorMap is used to map values into colors. More...

#include <qwt_color_map.h>

Inheritance diagram for QwtColorMap:

Public Types
enum	Format { RGB, Indexed }
Public Member Functions
	QwtColorMap (Format=QwtColorMap::RGB)
	Constructor.
virtual	~QwtColorMap ()
	Destructor.
Format	format () const
virtual QwtColorMap *	copy () const =0
	Clone the color map.
virtual QRgb	rgb (const QwtDoubleInterval &interval, double value) const =0
virtual unsigned char	colorIndex (const QwtDoubleInterval &interval, double value) const =0
QColor	color (const QwtDoubleInterval &, double value) const
virtual QValueVector< QRgb >	colorTable (const QwtDoubleInterval &) const

Detailed Description

QwtColorMap is used to map values into colors.

For displaying 3D data on a 2D plane the 3rd dimension is often displayed using colors, like f.e in a spectrogram.

Each color map is optimized to return colors for only one of the following image formats:

QImage::Format_Indexed8
QImage::Format_ARGB32

See also:: QwtPlotSpectrogram, QwtScaleWidget

Definition at line 44 of file qwt_color_map.h.

Member Enumeration Documentation

enum QwtColorMap::Format

RGB
The map is intended to map into QRgb values.
Indexed
The map is intended to map into 8 bit values, that are indices into the color table.

See also:: rgb(), colorIndex(), colorTable()

Enumerator:

RGB
Indexed

Definition at line 57 of file qwt_color_map.h.

    {
        RGB,
        Indexed
    };

Constructor & Destructor Documentation

QwtColorMap::QwtColorMap ( Format format = QwtColorMap::RGB )

Constructor.

Definition at line 164 of file qwt_color_map.cpp.

                                     :
    d_format(format)
{
}

QwtColorMap::~QwtColorMap ( ) [virtual]

Destructor.

Definition at line 170 of file qwt_color_map.cpp.

{
}

Member Function Documentation

QColor QwtColorMap::color	(	const QwtDoubleInterval &	interval,
		double	value
	)		const `[inline]`

Map a value into a color

Parameters:

interval	Valid interval for values
value	Value

Returns:: Color corresponding to value

Warning:: This method is slow for Indexed color maps. If it is necessary to map many values, its better to get the color table once and find the color using colorIndex().

Definition at line 198 of file qwt_color_map.h.

References colorIndex(), colorTable(), rgb(), and RGB.

{
    if ( d_format == RGB )
    {
        return QColor( rgb(interval, value) );
    }
    else
    {
        const unsigned int index = colorIndex(interval, value);
        return colorTable(interval)[index]; // slow
    }
}

virtual unsigned char QwtColorMap::colorIndex	(	const QwtDoubleInterval &	interval,
		double	value
	)		const `[pure virtual]`

Map a value of a given interval into a color index

Parameters:

interval	Range for the values
value	Value

Returns:: color index, corresponding to value

Implemented in QwtLinearColorMap.

Referenced by color(), QwtPainter::drawColorBar(), and QwtPlotSpectrogram::renderImage().

QwtColorTable QwtColorMap::colorTable ( const QwtDoubleInterval & interval ) const [virtual]

Build and return a color map of 256 colors

The color table is needed for rendering indexed images in combination with using colorIndex().

Parameters:

interval Range for the values

Returns:: A color table, that can be used for a QImage

Definition at line 183 of file qwt_color_map.cpp.

References int(), QwtDoubleInterval::isValid(), QwtDoubleInterval::minValue(), rgb(), and QwtDoubleInterval::width().

Referenced by color(), QwtPainter::drawColorBar(), and QwtPlotSpectrogram::renderImage().

{
    QwtColorTable table(256);

    if ( interval.isValid() )
    {
        const double step = interval.width() / (table.size() - 1);
        for ( int i = 0; i < (int) table.size(); i++ )
            table[i] = rgb(interval, interval.minValue() + step * i);
    }

    return table;
}