QPainter Class

QPainter Class

The QPainter class performs low-level painting on widgets and other paint devices. 

Header:	#include <QPainter>
qmake:	QT += gui
Inherited By:	QStylePainter

Public Types

class	PixmapFragment
enum	CompositionMode { CompositionMode_SourceOver, CompositionMode_DestinationOver, CompositionMode_Clear, CompositionMode_Source, CompositionMode_Destination, …, RasterOp_SourceOrNotDestination }
enum	PixmapFragmentHint { OpaqueHint }
flags	PixmapFragmentHints
enum	RenderHint { Antialiasing, TextAntialiasing, SmoothPixmapTransform, HighQualityAntialiasing, NonCosmeticDefaultPen, …, LosslessImageRendering }
flags	RenderHints

Public Functions

Public Functions

	QPainter(QPaintDevice *device)
	QPainter()
	~QPainter()
const QBrush &	background() const
Qt::BGMode	backgroundMode() const
bool	begin(QPaintDevice *device)
void	beginNativePainting()
QRectF	boundingRect(const QRectF &rectangle, int flags, const QString &text)
QRect	boundingRect(const QRect &rectangle, int flags, const QString &text)
QRect	boundingRect(int x, int y, int w, int h, int flags, const QString &text)
QRectF	boundingRect(const QRectF &rectangle, const QString &text, const QTextOption &option = QTextOption())
const QBrush &	brush() const
QPoint	brushOrigin() const
QRectF	clipBoundingRect() const
QPainterPath	clipPath() const
QRegion	clipRegion() const
QTransform	combinedTransform() const
QPainter::CompositionMode	compositionMode() const
QPaintDevice *	device() const
const QTransform &	deviceTransform() const
void	drawArc(const QRectF &rectangle, int startAngle, int spanAngle)
void	drawArc(const QRect &rectangle, int startAngle, int spanAngle)
void	drawArc(int x, int y, int width, int height, int startAngle, int spanAngle)
void	drawChord(const QRectF &rectangle, int startAngle, int spanAngle)
void	drawChord(int x, int y, int width, int height, int startAngle, int spanAngle)
void	drawChord(const QRect &rectangle, int startAngle, int spanAngle)
void	drawConvexPolygon(const QPointF *points, int pointCount)
void	drawConvexPolygon(const QPolygonF &polygon)
void	drawConvexPolygon(const QPoint *points, int pointCount)
void	drawConvexPolygon(const QPolygon &polygon)
void	drawEllipse(const QRectF &rectangle)
void	drawEllipse(const QRect &rectangle)
void	drawEllipse(int x, int y, int width, int height)
void	drawEllipse(const QPointF &center, qreal rx, qreal ry)
void	drawEllipse(const QPoint &center, int rx, int ry)
void	drawGlyphRun(const QPointF &position, const QGlyphRun &glyphs)
void	drawImage(const QRectF &target, const QImage &image, const QRectF &source, Qt::ImageConversionFlags flags = Qt::AutoColor)
void	drawImage(const QRect &target, const QImage &image, const QRect &source, Qt::ImageConversionFlags flags = Qt::AutoColor)
void	drawImage(const QPointF &point, const QImage &image, const QRectF &source, Qt::ImageConversionFlags flags = Qt::AutoColor)
void	drawImage(const QPoint &point, const QImage &image, const QRect &source, Qt::ImageConversionFlags flags = Qt::AutoColor)
void	drawImage(const QRectF &rectangle, const QImage &image)
void	drawImage(const QRect &rectangle, const QImage &image)
void	drawImage(const QPointF &point, const QImage &image)
void	drawImage(const QPoint &point, const QImage &image)
void	drawImage(int x, int y, const QImage &image, int sx = 0, int sy = 0, int sw = -1, int sh = -1, Qt::ImageConversionFlags flags = Qt::AutoColor)
void	drawLine(const QLineF &line)
void	drawLine(const QLine &line)
void	drawLine(int x1, int y1, int x2, int y2)
void	drawLine(const QPoint &p1, const QPoint &p2)
void	drawLine(const QPointF &p1, const QPointF &p2)
void	drawLines(const QLineF *lines, int lineCount)
void	drawLines(const QVector<QLineF> &lines)
void	drawLines(const QPointF *pointPairs, int lineCount)
void	drawLines(const QVector<QPointF> &pointPairs)
void	drawLines(const QLine *lines, int lineCount)
void	drawLines(const QVector<QLine> &lines)
void	drawLines(const QPoint *pointPairs, int lineCount)
void	drawLines(const QVector<QPoint> &pointPairs)
void	drawPath(const QPainterPath &path)
void	drawPicture(const QPointF &point, const QPicture &picture)
void	drawPicture(int x, int y, const QPicture &picture)
void	drawPicture(const QPoint &point, const QPicture &picture)
void	drawPie(const QRectF &rectangle, int startAngle, int spanAngle)
void	drawPie(int x, int y, int width, int height, int startAngle, int spanAngle)
void	drawPie(const QRect &rectangle, int startAngle, int spanAngle)
void	drawPixmap(const QRectF &target, const QPixmap &pixmap, const QRectF &source)
void	drawPixmap(const QRect &target, const QPixmap &pixmap, const QRect &source)
void	drawPixmap(int x, int y, int w, int h, const QPixmap &pixmap, int sx, int sy, int sw, int sh)
void	drawPixmap(int x, int y, const QPixmap &pixmap, int sx, int sy, int sw, int sh)
void	drawPixmap(const QPointF &point, const QPixmap &pixmap, const QRectF &source)
void	drawPixmap(const QPoint &point, const QPixmap &pixmap, const QRect &source)
void	drawPixmap(const QPointF &point, const QPixmap &pixmap)
void	drawPixmap(const QPoint &point, const QPixmap &pixmap)
void	drawPixmap(int x, int y, const QPixmap &pixmap)
void	drawPixmap(const QRect &rectangle, const QPixmap &pixmap)
void	drawPixmap(int x, int y, int width, int height, const QPixmap &pixmap)
void	drawPixmapFragments(const QPainter::PixmapFragment *fragments, int fragmentCount, const QPixmap &pixmap, QPainter::PixmapFragmentHints hints = PixmapFragmentHints())
void	drawPoint(const QPointF &position)
void	drawPoint(const QPoint &position)
void	drawPoint(int x, int y)
void	drawPoints(const QPointF *points, int pointCount)
void	drawPoints(const QPolygonF &points)
void	drawPoints(const QPoint *points, int pointCount)
void	drawPoints(const QPolygon &points)
void	drawPolygon(const QPointF *points, int pointCount, Qt::FillRule fillRule = Qt::OddEvenFill)
void	drawPolygon(const QPolygonF &points, Qt::FillRule fillRule = Qt::OddEvenFill)
void	drawPolygon(const QPoint *points, int pointCount, Qt::FillRule fillRule = Qt::OddEvenFill)
void	drawPolygon(const QPolygon &points, Qt::FillRule fillRule = Qt::OddEvenFill)
void	drawPolyline(const QPointF *points, int pointCount)
void	drawPolyline(const QPolygonF &points)
void	drawPolyline(const QPoint *points, int pointCount)
void	drawPolyline(const QPolygon &points)
void	drawRect(const QRectF &rectangle)
void	drawRect(int x, int y, int width, int height)
void	drawRect(const QRect &rectangle)
void	drawRects(const QRectF *rectangles, int rectCount)
void	drawRects(const QVector<QRectF> &rectangles)
void	drawRects(const QRect *rectangles, int rectCount)
void	drawRects(const QVector<QRect> &rectangles)
void	drawRoundedRect(const QRectF &rect, qreal xRadius, qreal yRadius, Qt::SizeMode mode = Qt::AbsoluteSize)
void	drawRoundedRect(int x, int y, int w, int h, qreal xRadius, qreal yRadius, Qt::SizeMode mode = Qt::AbsoluteSize)
void	drawRoundedRect(const QRect &rect, qreal xRadius, qreal yRadius, Qt::SizeMode mode = Qt::AbsoluteSize)
void	drawStaticText(const QPointF &topLeftPosition, const QStaticText &staticText)
void	drawStaticText(const QPoint &topLeftPosition, const QStaticText &staticText)
void	drawStaticText(int left, int top, const QStaticText &staticText)
void	drawText(const QRectF &rectangle, int flags, const QString &text, QRectF *boundingRect = nullptr)
void	drawText(const QPointF &position, const QString &text)
void	drawText(const QPoint &position, const QString &text)
void	drawText(int x, int y, const QString &text)
void	drawText(const QRect &rectangle, int flags, const QString &text, QRect *boundingRect = nullptr)
void	drawText(int x, int y, int width, int height, int flags, const QString &text, QRect *boundingRect = nullptr)
void	drawText(const QRectF &rectangle, const QString &text, const QTextOption &option = QTextOption())
void	drawTiledPixmap(const QRectF &rectangle, const QPixmap &pixmap, const QPointF &position = QPointF())
void	drawTiledPixmap(int x, int y, int width, int height, const QPixmap &pixmap, int sx = 0, int sy = 0)
void	drawTiledPixmap(const QRect &rectangle, const QPixmap &pixmap, const QPoint &position = QPoint())
bool	end()
void	endNativePainting()
void	eraseRect(const QRectF &rectangle)
void	eraseRect(int x, int y, int width, int height)
void	eraseRect(const QRect &rectangle)
void	fillPath(const QPainterPath &path, const QBrush &brush)
void	fillRect(const QRectF &rectangle, const QBrush &brush)
void	fillRect(int x, int y, int width, int height, const QBrush &brush)
void	fillRect(const QRect &rectangle, const QBrush &brush)
void	fillRect(const QRectF &rectangle, const QColor &color)
void	fillRect(int x, int y, int width, int height, const QColor &color)
void	fillRect(const QRect &rectangle, const QColor &color)
void	fillRect(int x, int y, int width, int height, Qt::GlobalColor color)
void	fillRect(const QRect &rectangle, Qt::GlobalColor color)
void	fillRect(const QRectF &rectangle, Qt::GlobalColor color)
void	fillRect(int x, int y, int width, int height, Qt::BrushStyle style)
void	fillRect(const QRect &rectangle, Qt::BrushStyle style)
void	fillRect(const QRectF &rectangle, Qt::BrushStyle style)
void	fillRect(int x, int y, int width, int height, QGradient::Preset preset)
void	fillRect(const QRect &rectangle, QGradient::Preset preset)
void	fillRect(const QRectF &rectangle, QGradient::Preset preset)
const QFont &	font() const
QFontInfo	fontInfo() const
QFontMetrics	fontMetrics() const
bool	hasClipping() const
bool	isActive() const
Qt::LayoutDirection	layoutDirection() const
qreal	opacity() const
QPaintEngine *	paintEngine() const
const QPen &	pen() const
QPainter::RenderHints	renderHints() const
void	resetTransform()
void	restore()
void	rotate(qreal angle)
void	save()
void	scale(qreal sx, qreal sy)
void	setBackground(const QBrush &brush)
void	setBackgroundMode(Qt::BGMode mode)
void	setBrush(const QBrush &brush)
void	setBrush(Qt::BrushStyle style)
void	setBrushOrigin(const QPointF &position)
void	setBrushOrigin(int x, int y)
void	setBrushOrigin(const QPoint &position)
void	setClipPath(const QPainterPath &path, Qt::ClipOperation operation = Qt::ReplaceClip)
void	setClipRect(const QRectF &rectangle, Qt::ClipOperation operation = Qt::ReplaceClip)
void	setClipRect(const QRect &rectangle, Qt::ClipOperation operation = Qt::ReplaceClip)
void	setClipRect(int x, int y, int width, int height, Qt::ClipOperation operation = Qt::ReplaceClip)
void	setClipRegion(const QRegion &region, Qt::ClipOperation operation = Qt::ReplaceClip)
void	setClipping(bool enable)
void	setCompositionMode(QPainter::CompositionMode mode)
void	setFont(const QFont &font)
void	setLayoutDirection(Qt::LayoutDirection direction)
void	setOpacity(qreal opacity)
void	setPen(const QPen &pen)
void	setPen(const QColor &color)
void	setPen(Qt::PenStyle style)
void	setRenderHint(QPainter::RenderHint hint, bool on = true)
void	setRenderHints(QPainter::RenderHints hints, bool on = true)
void	setTransform(const QTransform &transform, bool combine = false)
void	setViewTransformEnabled(bool enable)
void	setViewport(const QRect &rectangle)
void	setViewport(int x, int y, int width, int height)
void	setWindow(const QRect &rectangle)
void	setWindow(int x, int y, int width, int height)
void	setWorldMatrixEnabled(bool enable)
void	setWorldTransform(const QTransform &matrix, bool combine = false)
void	shear(qreal sh, qreal sv)
void	strokePath(const QPainterPath &path, const QPen &pen)
bool	testRenderHint(QPainter::RenderHint hint) const
const QTransform &	transform() const
void	translate(const QPointF &offset)
void	translate(const QPoint &offset)
void	translate(qreal dx, qreal dy)
bool	viewTransformEnabled() const
QRect	viewport() const
QRect	window() const
bool	worldMatrixEnabled() const
const QTransform &	worldTransform() const

Detailed Description

QPainter provides highly optimized functions to do most of the drawing GUI programs require. It can draw everything from simple lines to complex shapes like pies and chords. It can also draw aligned text and pixmaps. Normally, it draws in a "natural" coordinate system, but it can also do view and world transformation. QPainter can operate on any object that inherits the QPaintDevice class.

The common use of QPainter is inside a widget's paint event: Construct and customize (e.g. set the pen or the brush) the painter. Then draw. Remember to destroy the QPainter object after drawing. For example:

void SimpleExampleWidget::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    painter.setPen(Qt::blue);
    painter.setFont(QFont("Arial", 30));
    painter.drawText(rect(), Qt::AlignCenter, "Qt");
}

参考：https://doc.qt.io/qt-5/qpainter.html

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