Paint System

A system for painting on the screen or on print devices using the same API

Qt's paint system enables painting on screen and print devices using the same API, and is primarily based on the QPainter, QPaintDevice, and QPaintEngine classes.

QPainter is used to perform drawing operations, QPaintDevice is an abstraction of a two-dimensional space that can be painted on using a QPainter, and QPaintEngine provides the interface that the painter uses to draw onto different types of devices. The QPaintEngine class is used internally by QPainter and QPaintDevice, and is hidden from application programmers unless they create their own device type.

The main benefit of this approach is that all painting follows the same painting pipeline making it easy to add support for new features and providing default implementations for unsupported ones.

Topics

Classes for Painting

These classes provide support for painting onto a paint device.

QBitmap

Monochrome (1-bit depth) pixmaps

QBrush

Defines the fill pattern of shapes drawn by QPainter

QColor

Colors based on RGB, HSV or CMYK values

QColormap

Maps device independent QColors to device dependent pixel values

QConicalGradient

Used in combination with QBrush to specify a conical gradient brush

QDirectPainter

Direct access to the underlying hardware in Qt for Embedded Linux

QFont

Specifies a font used for drawing text

QFontMetrics

Font metrics information

QFontMetricsF

Font metrics information

QGenericMatrix

Template class that represents a NxM transformation matrix with N columns and M rows

QGradient

Used in combination with QBrush to specify gradient fills

QIcon

Scalable icons in different modes and states

QIconEngine

Abstract base class for QIcon renderers

QIconEngineV2

Abstract base class for QIcon renderers

QImage

Hardware-independent image representation that allows direct access to the pixel data, and can be used as a paint device

QImageReader

Format independent interface for reading images from files or other devices

QImageWriter

Format independent interface for writing images to files or other devices

QLine

Two-dimensional vector using integer precision

QLineF

Two-dimensional vector using floating point precision

QLinearGradient

Used in combination with QBrush to specify a linear gradient brush

QMargins

Defines the four margins of a rectangle

QMovie

Convenience class for playing movies with QImageReader

QPaintDevice

The base class of objects that can be painted

QPaintEngine

Abstract definition of how QPainter draws to a given device on a given platform

QPainter

Performs low-level painting on widgets and other paint devices

QPainterPath

Container for painting operations, enabling graphical shapes to be constructed and reused

QPainterPathStroker

Used to generate fillable outlines for a given painter path

QPalette

Contains color groups for each widget state

QPen

Defines how a QPainter should draw lines and outlines of shapes

QPicture

Paint device that records and replays QPainter commands

QPixmap

Off-screen image representation that can be used as a paint device

QPixmapCache

Application-wide cache for pixmaps

QPoint

Defines a point in the plane using integer precision

QPointF

Defines a point in the plane using floating point precision

QPolygon

Vector of points using integer precision

QPolygonF

Vector of points using floating point precision

QRadialGradient

Used in combination with QBrush to specify a radial gradient brush

QRect

Defines a rectangle in the plane using integer precision

QRectF

Defines a rectangle in the plane using floating point precision

QRegion

Specifies a clip region for a painter

QSize

Defines the size of a two-dimensional object using integer point precision

QSizeF

Defines the size of a two-dimensional object using floating point precision

QStylePainter

Convenience class for drawing QStyle elements inside a widget

QSvgGenerator

Paint device that is used to create SVG drawings

QSvgRenderer

Used to draw the contents of SVG files onto paint devices

QSvgWidget

Widget that is used to display the contents of Scalable Vector Graphics (SVG) files

QTransform

Specifies 2D transformations of a coordinate system

QVector2D

Represents a vector or vertex in 2D space

Alternatively, Qt provides the QtOpenGL module, offering classes that makes it easy to use OpenGL in Qt applications. Among others, the module provides an OpenGL widget class that can be used just like any other Qt widget, except that it opens an OpenGL display buffer where the OpenGL API can be used to render the contents.

Notes provided by the Qt Community

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