A helper class for translating a series of points 更多...

#include <qwt_point_mapper.h>

类
class	PrivateData

Public 类型
enum	TransformationFlag { RoundPoints = 0x01 , WeedOutPoints = 0x02 , WeedOutIntermediatePoints = 0x04 , PixelColumnReduce = 0x08 , LTTBReduce = 0x20 , MinMaxReduce = 0x10 , AdaptiveColumnReduce = 0x40 }
	Flags affecting the transformation process 更多...

Public 成员函数
	QwtPointMapper ()
	Constructor

void	setFlags (TransformationFlags)
	Set the flags affecting the transformation process

TransformationFlags	flags () const
	Get the flags affecting the transformation process

void	setFlag (TransformationFlag, bool on=true)
	Modify a flag affecting the transformation process

bool	testFlag (TransformationFlag) const
	Test if a flag is set

void	setBoundingRect (const QRectF &)
	Set a bounding rectangle for the point mapping algorithm

QRectF	boundingRect () const
	Get the bounding rectangle

void	setDevicePixelRatio (qreal ratio)
	Set the device pixel ratio of the target paint device

qreal	devicePixelRatio () const
	Get the device pixel ratio of the target paint device

QPolygonF	toPolygonF (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QwtSeriesData< QPointF > *series, int from, int to) const
	Translate a series of points into a QPolygonF

QPolygon	toPolygon (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QwtSeriesData< QPointF > *series, int from, int to) const
	Translate a series of points into a QPolygon

QPolygon	toPoints (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QwtSeriesData< QPointF > *series, int from, int to) const
	Translate a series of points into a QPolygon (scattered points)

QPolygonF	toPointsF (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QwtSeriesData< QPointF > *series, int from, int to) const
	Translate a series into a QPolygonF (scattered points)

QImage	toImage (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QwtSeriesData< QPointF > *series, int from, int to, const QPen &, bool antialiased, uint numThreads) const
	Translate a series into a QImage

详细描述

A helper class for translating a series of points

QwtPointMapper is a collection of methods and optimizations for translating a series of points into paint device coordinates. It is used by QwtPlotCurve but might also be useful for similar plot items displaying a QwtSeriesData<QPointF>.

成员枚举类型说明

◆ TransformationFlag

enum QwtPointMapper::TransformationFlag

Flags affecting the transformation process

参见: setFlag(), setFlags()

枚举值
RoundPoints	Round points to the device pixel grid ( see devicePixelRatio() )
WeedOutPoints	Try to remove points, that are translated to the same position
WeedOutIntermediatePoints	An even more aggressive weeding algorithm An even more aggressive weeding algorithm, that can be used in toPolygon(). A consecutive chunk of points being mapped to the same x coordinate is reduced to 4 points: first point point with the minimum y coordinate point with the maximum y coordinate last point In the worst case (first and last points are never one of the extremes) the number of points will be 4 times the width. As the algorithm is fast it can be used inside of a polyline render cycle.
PixelColumnReduce	Pixel-column based downsampling Allocates a bin array indexed by device pixel column ( see devicePixelRatio() ) and stores first/min/max/last Y per column. Output is at most 4 points per column. Requires a valid boundingRect() to determine the canvas width. Overrides WeedOutIntermediatePoints when both are set.
LTTBReduce	Largest-Triangle-Three-Buckets (LTTB) downsampling Divides the visible data into equal-count buckets and keeps the sample of each bucket, that forms the largest triangle with the previously selected point and the average of the next bucket. The first and last sample are always kept. Target bucket count is 4 * boundingRect() width in device pixels ( see devicePixelRatio() ), the output is at most one point per bucket. Overrides WeedOutIntermediatePoints when both are set.
MinMaxReduce	MinMax bucket downsampling Divides the visible data into equal-count buckets and keeps the min-Y and max-Y point from each bucket. Target bucket count is derived from boundingRect() width in device pixels ( see devicePixelRatio() ). Overrides WeedOutIntermediatePoints when both are set.
AdaptiveColumnReduce	Adaptive column reduce downsampling Single pass O(n) reduction combining a density gate with an ordered vertical tolerance selection, all pixel quantities in device pixels ( see devicePixelRatio() ): When the visible samples are not denser than 2 points per device pixel column the data is mapped 1:1 without any reduction, so zooming in always restores full fidelity. Otherwise the samples are clustered by device pixel column. Inside a cluster the first sample, every sample whose mapped y differs by at least 1 device pixel from the last kept sample and the last sample are kept - in their original order and at their real sub pixel coordinates. In contrast to the min/max envelope per column ( PixelColumnReduce ) ramps stay ramps instead of degenerating into a 1px staircase of vertical strokes and horizontal steps. When this selection of a cluster would emit more than K = 4 + ( cluster y span in device pixels ) points ( high frequency noise inside one column ) the cluster falls back to an ordered first/min/max/last quadruple, so the output per column is bounded by K + 1 points. The deviation from the original curve is bounded by 1 device pixel vertically and one column horizontally, visible features of at least 1 device pixel ( including in-column extrema and spikes ) are kept in sample order. For smooth data the output size is roughly the vertical pixel travel. Overrides all other reduction flags when set.

构造及析构函数说明

◆ QwtPointMapper()

QwtPointMapper::QwtPointMapper ( )

Constructor

Creates a QwtPointMapper with default settings.

Destructor

Destroys the QwtPointMapper and frees all allocated resources.

成员函数说明

◆ boundingRect()

QRectF QwtPointMapper::boundingRect ( ) const

Get the bounding rectangle

返回: Bounding rectangle

参见: setBoundingRect()

◆ devicePixelRatio()

qreal QwtPointMapper::devicePixelRatio ( ) const

Get the device pixel ratio of the target paint device

返回: Device pixel ratio

参见: setDevicePixelRatio()

◆ flags()

QwtPointMapper::TransformationFlags QwtPointMapper::flags ( ) const

Get the flags affecting the transformation process

返回: Flags affecting the transformation process

参见: setFlags(), setFlag()

◆ setBoundingRect()

void QwtPointMapper::setBoundingRect ( const QRectF & rect )

Set a bounding rectangle for the point mapping algorithm

A valid bounding rectangle can be used for optimizations.

参数

[in] rect Bounding rectangle

参见: boundingRect()

◆ setDevicePixelRatio()

void QwtPointMapper::setDevicePixelRatio ( qreal ratio )

Set the device pixel ratio of the target paint device

All pixel based reductions ( bucket counts, pixel columns ) and the rounding of RoundPoints are calculated in device pixels of the target paint device. On high DPI screens ( ratio > 1 ) this keeps the resolution of the reduction and the granularity of the rounding aligned with what the device can actually display. The mapped coordinates themselves remain in paint coordinates.

参数

[in] ratio Device pixel ratio - values <= 0 are reset to 1.0

参见: devicePixelRatio(), QwtPainter::devicePixelRatio()

◆ setFlag()

void QwtPointMapper::setFlag	(	TransformationFlag	flag,
		bool	on = `true`
	)

Modify a flag affecting the transformation process

参数

[in]	flag	Flag type
[in]	on	Value

参见: testFlag(), setFlags()

◆ setFlags()

void QwtPointMapper::setFlags ( TransformationFlags flags )

Set the flags affecting the transformation process

参数

[in] flags Flags

参见: flags(), setFlag()

◆ testFlag()

bool QwtPointMapper::testFlag ( TransformationFlag flag ) const

Test if a flag is set

参数

[in] flag Flag type

返回: True when the flag is set

参见: setFlag(), setFlags()

◆ toImage()

QImage QwtPointMapper::toImage	(	const QwtScaleMap &	xMap,
		const QwtScaleMap &	yMap,
		const QwtSeriesData< QPointF > *	series,
		int	from,
		int	to,
		const QPen &	pen,
		bool	antialiased,
		uint	numThreads
	)		const

Translate a series into a QImage

参数

[in]	xMap	x map
[in]	yMap	y map
[in]	series	Series of points to be mapped
[in]	from	Index of the first point to be painted
[in]	to	Index of the last point to be painted
[in]	pen	Pen used for drawing a point of the image, where a point is mapped to
[in]	antialiased	True when the dots should be displayed antialiased
[in]	numThreads	Number of threads to be used for rendering. If numThreads is set to 0, the system specific ideal thread count is used.

返回: Image displaying the series

◆ toPoints()

QPolygon QwtPointMapper::toPoints	(	const QwtScaleMap &	xMap,
		const QwtScaleMap &	yMap,
		const QwtSeriesData< QPointF > *	series,
		int	from,
		int	to
	)		const

Translate a series of points into a QPolygon (scattered points)

WeedOutPoints & boundingRect().isValid(): All points that are mapped to the same position will be one point. Points outside of the bounding rectangle are ignored.
WeedOutPoints & !boundingRect().isValid(): All consecutive points that are mapped to the same position will one point.
!WeedOutPoints & boundingRect().isValid(): Points outside of the bounding rectangle are ignored.

参数

[in]	xMap	x map
[in]	yMap	y map
[in]	series	Series of points to be mapped
[in]	from	Index of the first point to be painted
[in]	to	Index of the last point to be painted

返回: Translated polygon

◆ toPointsF()

QPolygonF QwtPointMapper::toPointsF	(	const QwtScaleMap &	xMap,
		const QwtScaleMap &	yMap,
		const QwtSeriesData< QPointF > *	series,
		int	from,
		int	to
	)		const

Translate a series into a QPolygonF (scattered points)

WeedOutPoints & RoundPoints & boundingRect().isValid(): All points that are mapped to the same position will be one point. Points outside of the bounding rectangle are ignored.
WeedOutPoints & RoundPoints & !boundingRect().isValid(): All consecutive points that are mapped to the same position will one point.
WeedOutPoints & !RoundPoints: All consecutive points that are mapped to the same position will one point.
!WeedOutPoints & boundingRect().isValid(): Points outside of the bounding rectangle are ignored.

When RoundPoints is set, all points are rounded to the device pixel grid ( see devicePixelRatio() ) but returned as PolygonF - what only makes sense when the further processing of the values need a QPolygonF.

参数

[in]	xMap	x map
[in]	yMap	y map
[in]	series	Series of points to be mapped
[in]	from	Index of the first point to be painted
[in]	to	Index of the last point to be painted

返回: Translated polygon

◆ toPolygon()

QPolygon QwtPointMapper::toPolygon	(	const QwtScaleMap &	xMap,
		const QwtScaleMap &	yMap,
		const QwtSeriesData< QPointF > *	series,
		int	from,
		int	to
	)		const

Translate a series of points into a QPolygon

When the WeedOutPoints flag is enabled, consecutive points that are mapped to the same position will be one point.

参数

[in]	xMap	x map
[in]	yMap	y map
[in]	series	Series of points to be mapped
[in]	from	Index of the first point to be painted
[in]	to	Index of the last point to be painted

返回: Translated polygon

◆ toPolygonF()

QPolygonF QwtPointMapper::toPolygonF	(	const QwtScaleMap &	xMap,
		const QwtScaleMap &	yMap,
		const QwtSeriesData< QPointF > *	series,
		int	from,
		int	to
	)		const

Translate a series of points into a QPolygonF

When the WeedOutPoints flag is enabled, consecutive points that are mapped to the same position will be one point. When RoundPoints is set, all points are rounded to the device pixel grid ( see devicePixelRatio() ) but returned as PolygonF - what only makes sense when the further processing of the values need a QPolygonF. When WeedOutIntermediatePoints is enabled, an even more aggressive weeding algorithm is enabled. It rounds to device pixels on its own and does not require RoundPoints to be set.

参数

[in]	xMap	x map
[in]	yMap	y map
[in]	series	Series of points to be mapped
[in]	from	Index of the first point to be painted
[in]	to	Index of the last point to be painted

返回: Translated polygon

该类的文档由以下文件生成:

/home/runner/work/QWT/QWT/src/plot/qwt_point_mapper.h
/home/runner/work/QWT/QWT/src/plot/qwt_point_mapper.cpp

类

Public 类型

Public 成员函数

详细描述

成员枚举类型说明

◆ TransformationFlag

构造及析构函数说明

◆ QwtPointMapper()

成员函数说明

◆ boundingRect()

◆ devicePixelRatio()

◆ flags()

◆ setBoundingRect()

◆ setDevicePixelRatio()

◆ setFlag()

◆ setFlags()

◆ testFlag()

◆ toImage()

◆ toPoints()

◆ toPointsF()

◆ toPolygon()

◆ toPolygonF()